Exam 4

four basic types of volcanoes

(a) shield volcano, (b) cinder cone, (c) composite cone, also known as stratovolcano, and (d) plug dome

Good Soil

(about 3% of Earth) represents areas with good soils for agriculture to feed the world's population

NRCS Soil Orders

12 soil orders based on a variety of characteristics and processes that can be recognized by examining a soil and its profile

Mesozoic Era

248 million to 65 million years ago, a time when the large continents of Gondwana and Laurasia each gradually split apart as new ocean floors widened, creating the continents that are familiar to us today, the age of the dinosaurs, but other life also thrived, such as marine plants and invertebrates, reptiles, insects, mammals, and the earliest birds, ended with a great extinction event that included the end of the dinosaurs and virtually all large terrestrial animals

schist

A common metamorphic rock with thin foliation layers

Spodic horizon

A dark colored layer beneath an A2 horizon formed by the illuviation of humus and oxides of aluminum and/or iron

Mollic epipedon

A dark-colored surface layer with a high content of basic substances (calcium, magnesium, and potassium)

Ochric epipedon

A light-colored surface horizon that is either very low in organic matter or very thin

Albic horizon

A sandy and light-colored A2 horizon above a spodic horizon, because of the removal of clay and iron oxides

clay minerals

A small (clay-sized) hydrous aluminum silicate material typically created by chemical weathering, especially hydrolysis, commonly occupy cracks and voids in rocks and are subject to hydration and dehydration

Salic horizon

A soil layer, common in desert basins, that is at least 6 inches thick and contains at least 2% salt

Calcic horizon

A subsurface horizon that is rich in accumulated calcium carbonate or magnesium carbonate

Gypsic horizon

A subsurface soil horizon that is rich in accumulated gypsum

Black Soil

A very dark color may indicate a high amount of organic material present in the soil

Acidity and Alkalinity

An important aspect of soil chemistry is acidity, alkalinity (baseness), or neutrality, can affect the nutrients that are available for plant growth, Plants absorb nutrients that are dissolved in liquid. However, soil water that lacks some degree of acidity has little ability to dissolve these nutrients

flowing artesian wells

Artificially dug outlet that allows naturally pressurized groundwater to flow to Earth's surface, water tapped by the well rises to the ground surface and flows out onto the surface under its own pressure, without pumping

O horizon

At the surface, but only in locations where there is a sufficient cover of decomposed vegetation litter, a layer of organic debris and humus

plastic asthenosphere

Below the lithosphere, but still in the upper part of the mantle

E horizon

Beneath the A horizon, lighter-colored, named for the action of strong eluviation

clasts

Broken fragments of rock

clasts

Broken fragments of solids, solid broken piece of rock, bone, or shell, In order of increasing size, clasts range from clay, silt, and sand, to gravel, which is a general category for any fragment larger than sand (larger than 2.0 mm) and includes granules, pebbles, cobbles, and boulders, consist of fragments of previously existing rocks, shells, or bones that were deposited on a river bed, beach, sand dune, lake bottom, the ocean floor, and other environments where fragments of solids accumulate

Chemical Elements in Soils

Carbon, hydrogen, nitrogen, sodium, potassium, zinc, copper, iodine, and compounds of these elements

ions

Charged particles, form part of a molecule in a mineral that may leave or be traded for other substances, generally weakening the mineral structure and forming the chemical basis of rock weathering

lithospheric plates

Earth's exterior is broken into several of these large regions (plates) of rigid and brittle crust and upper mantle (lithosphere), large segments of the structural lithosphere, By acknowledging that the entire lithosphere, rather than just continental crust, is broken into multiple sections that move, the theory of plate tectonics allows a plausible explanation, which had eluded Wegener, of the driving force for the movement—convection in the mantle

mass wasting

Gravity-induced downslope movement of rock material that happens without the assistance of a geomorphic agent, as in the case of a rock falling from a cliff

Cl, O, R, P, T

Hans Jenny's list of soil formation factors: Climate, Organics, Relief, Parent material, and Time

freshwater

Ice and snow in the polar regions represent 70% of the freshwater on Earth, but it is generally unavailable for human use, rivers and lakes represent less than 1% of this crucial resource. The remaining freshwater, nearly 30%, lies close to, but beneath, Earth's surface. These underground resources make up an impressive 90% of the freshwater that is readily available for human use

solution sinkholes

If the depressions result primarily from the surface or near-surface solution of rock and removal of the dissolved materials by water infiltrating downward into the subsurface, tend to be funnel-shaped

Light Brown or Gray Soil Color

If the humus content is low because of limited organic activity or loss of organics through leaching

piedmont fault scarp

In areas of normal faults, unconsolidated sediments eroded from the uplifted block are deposited at the base of the slope near the fault zone and extending onto the downdropped block. If subsequent movement along the fault vertically offsets those unconsolidated sediments, it produces a piedmont fault scarp in the sediments

Accumulation of Humus

In hot equatorial regions, intense activities by soil microorganisms preclude a thick accumulation of organic debris or humus, the amounts of organic matter and humus in a soil increase toward the middle latitudes and away from polar regions and the tropics

light gray or white soil

In moist climates, indicates that iron has been leached out, leaving oxides of silicon and aluminum, but in dry climates, the same color typically indicates an accumulation of calcium or salts

Soil Degradation and Soil Loss

Land degradation by humans is a major cause of soil loss but impacts from changing climates, particularly desertification, also play a role, Overgrazing, deforestation, overuse of the land, and poor agricultural practices are the major human-related causes of soil loss

Slow Mass Wasting

Landscapes dominated by slow mass wasting tend toward rounded hillcrests and an absence of sharp angular features

Argillic horizon

Layer beneath the A horizon by illuviation containing a high content of accumulated clays

marble

Limestone is metamorphosed into this much denser rock, impurities in the rock can produce a beautiful variety of colors, nonfoliated metamorphic rocks

extrusive igneous rock

Molten material that solidifies at Earth's surface, rock solidified at Earth's surface from lava; also called volcanic rock, made from lava

magma

Molten rock matter below Earth's surface, molten (melted) rock matter located beneath Earth's surface from which intrusive igneous rocks are formed

More about Soil

Most soils are actually microenvironments teeming with life that ranges from bacteria and fungi to earthworms, rodents, and other burrowers. Animals mix organic material deeper into the soil, and move inorganic fragments toward the surface. In addition, plants and their root systems are integral parts of the soil-forming system. Particularly strong relationships exist between a soil and its location's vegetation and climate.

calcretes

Much thicker accumulations form by the upward (capillary) movement of dissolved calcium in groundwater when the water table is near the surface

lahars

Mudflows composed of volcanic ash, rapid, gravity-driven downslope movement of wet, fine-grained volcanic sediment

joint set

Multiple joints that parallel each other in a rock, two joint sets will cross each other at an angle, preferential weathering and erosion in crossing joint sets leave rock in the central area between the fractures only slightly weathered, whereas the rock near the fractures acquires a more rounded appearance

Ogallala Aquifer

One of the largest aquifers supplying groundwater for irrigation, an artesian system also known as the High Plains aquifer, which underlies the Great Plains from west Texas northward to South Dakota, supplies more than 30% of the groundwater used for irrigation in the United States

caliche

Over hundreds to thousands of years, the calcium carbonate enriched dust concentrates in the B horizon, forming hard layers

Seismic Waves

P and S waves are either refracted or reflected when they reach the zones of major density change that mark the boundaries between Earth's various interior layers, Seismic waves refract if they cross a boundary and continue traveling but with a shift in direction caused by the change in material density. Waves that reflect bounce off the boundary and do not enter the next layer. Both P and S waves speed up in denser material and slow down when passing through material that is less dense, Velocity of seismic P (primary) waves increases with depth as material density increases.

Inclination

Paleoinclinations recorded from ancient basalts provide the latitude of their location at the time of cooling, Earth's magnetic field encircles the planet and makes a magnetized dip needle point downward at an angle that equals the latitude of the needle's location

Factors Affecting Soil Formation

Parent Material, Organic Activity, Climate, Relief, Time

Soil Air

Perhaps as much as nearly 50% of a soil consists of open spaces between soil particles and clumps (aggregates of soil particles), Compared to the composition of the lower atmosphere, the air in a soil is likely to have less oxygen, more carbon dioxide, and a fairly high relative humidity because of the presence of capillary and hygroscopic water, For most microorganisms and plants that live in the ground, soil air supplies oxygen and carbon dioxide necessary for life processes

productivity potential

Plants need a variety of chemical substances for growth, and knowing a soil's mineral and chemical content is necessary for determining this

fold limbs

Rock layers that form the flanks of anticlinal crests and synclinal troughs

fine-grained texture

Rocks composed of small-sized individual minerals not visible to the unaided eye

clastic sedimentary rocks

Sedimentary rocks that form from fragments of preexisting rocks, shells, or bones, rock formed by the compaction and cementation of preexisting rock debris, Examples of clastic sedimentary rocks include conglomerate, sandstone, siltstone, and shale

Tectonic Plates

Seven major plates have proportions as large as or larger than continents or ocean basins. Five other plates are of minor size, although they have maintained their own identity and direction of movement for some time. Several additional plates are even smaller and exist in active zones at the boundaries between major plates. All major plates consist of both continental and oceanic crust, although the largest, the Pacific plate, is primarily oceanic. In some places, plates pull away from each other (diverge), in other places they push together (converge), and elsewhere they slide alongside each other (move laterally).

quartzite

Silica-rich sandstones fuse into this, brittle, harder than steel, and almost inert chemically. It is virtually immune to chemical weathering and commonly forms cliffs or rugged mountain peaks after the surrounding, less resistant rocks have been removed by erosion, nonfoliated metamorphic rocks

Gravitational Attraction

Sir Isaac Newton determined that the degree to which particles are drawn to each other by gravity depends in part on the mass of each particle, which is commonly expressed in units of grams (g) or kilograms (kg), gravitational force of attraction is greater for objects that have a larger mass than for those with a smaller mass, Earth materials that have the greatest density have the greatest gravitational force of attraction

rockslides

Slides of large sections of bedrock, are common in mountainous terrain where originally horizontal sedimentary rock layers have been tilted by tectonism, most common in wet years, or after a rainstorm or snowmelt

residual soils

Soils developed on a bedrock surface

Time

Soils have a tendency to develop toward a state of equilibrium with their environment, A soil is sometimes called "mature" when it has reached such an equilibrium condition, as soils develop, their influence of their parent material decreases and they increasingly reflect their climate and vegetative environments

Soil Color

Soils vary in color from black to brown to red, yellow, gray, and near-white. A soil's color is typically related to its physical and chemical characteristics.

Slope

Steep slopes are generally better drained than gentler ones, and they are also subject to rapid runoff of surface water, less infiltration of water on steeper slopes, which inhibits soil development, sometimes to the extent that there might be no soil, On gentler slopes, where there is less runoff and higher infiltration, more water is available to encourage soil development and to support vegetation growth, and erosion is not as intense

Acidic Soils

Strongly acidic soils are also detrimental to plant growth, can generally be corrected by adding lime to the soil

Oxic horizon

Subsurface horizon, in low-elevation tropical and subtropical climates containing oxides of iron and aluminum

Polarity

The basaltic seafloor has recorded the polarity history of Earth's magnetic field and the widening of the Atlantic Ocean

Organic Matter or Humus

The decayed remains of plant and animal materials, partially transformed by bacterial action, organic matter found in the surface soil layers that is in various stages of decomposition as a result of bacterial action, an important catalyst in chemical reactions that help plants extract soil nutrients, Soils that are rich in humus are workable and have a good capacity for water retention, also provides an abundant food source for microscopic soil organisms

magnetic dip

The magnetic field surrounding Earth causes a magnetic compass needle not only to point north but also to dip downward in a straight-line direction to north, a needle's angle off of horizontal approximates its latitudinal location

Landform Development by Solution

The principal mechanical role of subsurface water in landform development is to encourage mass movement by adding weight and reducing the strength of soil and sediments, thereby contributing to slumps, mud or debris slides, mud or debris flows, and landslides, Through the chemical breakdown of rock materials by carbonation and other forms of solution, and the deposition of those dissolved substances elsewhere, underground water is an effective land-shaping agent, especially in areas where limestone is present

reverse fault

The steep, high-angle fault resulting from compressional forces, high angle break with rocks on one side pushed up relative to those on the other side by compressional forces; hanging wall up, footwall down

Blue, Silver, Gray Soil

These tones mean that the soil has likely been reduced; in other words, oxygen has been removed from the soil

White Soil

Usually means that calcium carbonate or salts (such as NaCl) may be present in the soil

gravitational water

Water that percolates down through a soil under the force of gravity, meteoric water that passes through the soil under the influence of gravitation, moves downward through voids between soil particles and toward the water table, The quantity of gravitational water in a soil is related to several conditions, including the amount of precipitation, the time since it fell, evaporation rates, the space available for water storage, and how easily the water can move through the soil. As gravitational water percolates downward, it dissolves soluble minerals and carries them into deeper levels of the soil, perhaps to the zone where all open spaces are saturated. Gravitational water moving down through a soil also can wash the finer solid particles (clay and silt) away from upper soil layers

earthflow

When a relatively thick unit of predominantly fine-grained, unconsolidated hillside sediment or shale becomes saturated and mixes and tumbles as it moves, Earthflows occur as independent gravity-induced events or in association with slumps in a compound feature called a slump-earthflow

intrusive igneous rock

When molten rock beneath Earth's surface, that is, magma, changes to a solid (freezes), rock that solidified within Earth from magma; also called plutonic rock, Large masses of intrusive rock matter solidifying deep inside Earth cool very slowly because, like all rocks, those surrounding the magma are poor conductors and inhibit heat loss, Slow cooling allows more time for crystal formation prior to solidification

igneous rock

When molten rock material cools and solidifies, one of the three major categories of rock; formed from the cooling and solidification of molten rock matter, classified in terms of their mineral composition as well as the size of constituent minerals, which is referred to as texture, Igneous rocks are distinguished on the basis of texture (crystal size) and whether their mineral composition is mafic, felsic, or intermediate, Rocks that cool rapidly, at or near Earth's surface, have fine (small) crystals. Those that cool slowly, deep beneath the surface, have coarse crystalline texture (large crystals), Many igneous rocks are fractured, often by multiple cracks that may be evenly spaced or arranged in regular geometric patterns

thrust fault

Where compression pushes a mass of rock along a low-angle fault so that it overrides rocks on the other side of the fault, low angle break with rocks on one side pushed over those of the other side by compressional forces

platy

Where foliation layers are moderately thin, individual minerals exhibit a flattened elongate structure, rocks tend to flake apart along these bands

dolomite

Where magnesium is a major constituent along with calcium carbonate, chemical precipitate sedimentary rock

gneiss

Where the foliation develops into broad mineral bands, the rock is extremely hard, Coarse-grained rocks, such as granite, generally metamorphose into gneiss, whereas fine-grained rocks tend to become schist

aa

a blocky, angular surface of a lava flow, sharp-edged, jagged blocks, Lavas of slightly greater viscosity flow more slowly, allowing a thicker surface layer to harden while the still-molten interior lava keeps on flowing

geologic timescale

a calendar of Earth history, divided into eras, which are long units of time, and eras are divided into periods, Epochs are shorter time units and are used to subdivide the periods of the Cenozoic Era, for which geologic evidence is more abundant, Today, we are in the Holocene Epoch (last 10,000 years) of the Quaternary Period (last 2.6 million years) of the Cenozoic Era (last 65 million years).

island arcs

a chain of volcanic islands along a deep oceanic trench; found near tectonic plate boundaries where subduction is occurring, Where oceanic crust lies on both sides of a convergent plate boundary, the plate with the denser oceanic crust subducts below the other plate, composed of relatively low density rock and are not subducted down into the trench with the oceanic plate

solution

a chemical reaction causes mineral-forming ions to dissociate and the separated ions are carried away in the water, dissolving material in a fluid, such as water, or the liquid containing dissolved material; water transports dissolved load in solution, Most minerals that are insoluble or only slightly soluble in pure water will dissolve more readily if the water is acidic.

carbonation

a common type of solution that involves carbon dioxide and water molecules reacting with, and thereby decomposing, rock material, carbon dioxide in water chemically combining with other substances to create new compounds, most effective on carbonate rocks, particularly limestone, which is an abundant sedimentary rock composed of calcium carbonate, carbonate rocks overall, tend to weather extensively in humid regions but are resistant and often form cliffs in arid climates

Groundwater

a critical natural resource for large numbers of people and wildlife. Half the population of the United States derives its drinking water from groundwater, groundwater is often described as "hard water," in comparison with "softer" (less mineralized) rainwater

quartz

a crystalline silica; as a crystal, it adopts a distinctive prismatic shape. Because it is one of the last silicate minerals to form from solidifying molten rock matter, it is a relatively hard and resistant mineral

subsurface horizons

a distinct horizontal soil layer that lies beneath the surface, characteristic of vertical zonation in soils

strike-slip fault

a fault with horizontal motion, where movement takes place along the strike of the fault, the direction of slip-page is parallel to the surface trace, or strike, of the fault, also called a a lateral fault, The direction of motion along a strike-slip fault is described as left lateral or right lateral. Direction of motion is determined by imagining yourself standing on one block looking across the strike-slip fault to assess if the other block moved to your left or right.

Granite

a felsic, coarse-grained, intrusive rock, has the same chemical and mineral composition as rhyolite, a fine-grained, extrusive rock

viscosity

a fluid's resistance to flowing, Variations in eruptive style and in the landforms produced by volcanism stem mainly from differences in the viscosity of the magma feeding the eruption and in its gas content, Viscosity and gas content are determined especially by the chemical properties of the magma, but temperature is also involved, The primary material component that contributes to a higher viscosity in molten rock is silica content, Everything else being equal, because they are rich in silica, felsic magmas have a higher viscosity than mafic magmas, which contain less silica, an increase in temperature reduces to at least some extent the viscosity of any type of magma (makes it flow more easily), Magma viscosity influences the explosiveness of a volcanic eruption through its effect on the gas content of the magma

Shearing tectonic forces

a force that works to move two objects past each other in opposite directions, slide parts of Earth's crust past each other, Vertical displacement along a fault occurs when the rocks on one side move up or drop down relative to rocks on the other side

Regolith

a generic term for broken bedrock fragments at or very near the surface

Thermal springs

a groundwater spring flowing with hot or warm water, often with a high dissolved mineral content, have water temperatures that are higher than the surrounding mean annual atmospheric temperature and are further separated into warm springs and hot springs

sill

a horizontal sheet of igneous rock intruded and solidified between other rock layers, Magma sometimes intrudes between rock layers without doming them upward, solidifying as a horizontal sheet of intrusive igneous rock

caldera

a large depression formed by a volcanic eruption, often a crater formed by the inward collapse of a volcano

batholith

a large, irregular mass of intrusive igneous rock (pluton) at least (40 sq mi) in size, complex masses of solidified magma, usually granite, represent large plutons that, during their development kilometers beneath Earth's surface, melted, metamorphosed, or pushed aside other rocks, form the core of many major mountain ranges

Conglomerate

a lithified mass of cemented, roughly rounded pebbles, cobbles, and boulders and may have clay, silt, or sand filling in spaces between those larger particles

outcrop

a mass of bedrock exposed at Earth's surface that is not concealed by regolith or soil

hot spots

a mass of hot molten rock material at a fixed location beneath a lithospheric plate, a mass of molten rock in the mantle that does not move with the lithospheric plate, occur in both continental and oceanic locations, created each of the volcanic Hawaiian Islands in succession

igneous intrusions

a mass of igneous rock that cooled and solidified beneath the surface, also called plutons

earthquake intensity

a measure of the impact of an earthquake on humans and their built environment

relief

a measurement or expression of the difference between the highest and lowest location (or point) in a specified area or surface feature

geomorphic agent

a medium that erodes, transports, and deposits Earth materials; includes water, wind, and glacial ice, a medium that picks up, moves, and eventually lays down pieces of broken or dissolved rock matter

episodic processes

a period of relative calm and little change continues until a certain threshold condition is reached, resulting in a short burst of rapid, often intense activity that causes significant environmental modification, Many physical processes in the Earth system operate according to this punctuated equilibrium

isostatic depression

a process in which the lithosphere subsides, until it attains a new equilibrium level, as a result of a massive accumulation of glacial ice, lake water, or sediments

isostatic rebound

a process in which the region will tend to rise if the surface accumulation is later removed

soil surveys

a publication that describes the soil types in an area and includes maps that show their distribution, books that outline and describe the kinds of soils in a region and include maps of the distribution of soil types, usually at the county level.

Calcite

a relatively soft but widespread mineral that consists of one atom of calcium (Ca) linked together with a carbonate molecule, which is composed of one atom of carbon (C) plus three atoms of oxygen (O)

rock cycle

a representation of the processes and pathways by which Earth material becomes different types of rocks, a conceptual model for understanding processes that generate, alter, transport, and deposit mineral materials to produce different kinds of rocks

discontinuity

a significant change of density, The interface between the mantle and the overlying crust is marked by a significant change of density, indicated by an abrupt decrease in the velocity of seismic waves as they travel up through this internal boundary

Gully erosion or gullying

a significant problem that can often be avoided or overcome by proper agricultural practices, can alter the landscape to the point that the original productivity of the land cannot be regained

Pangaea

a single supercontinent, later divided into two large landmasses, one in the Southern Hemisphere (Gondwana) and one in the Northern Hemisphere (Laurasia)

pahoehoe

a smooth, ropy surface of a lava flow, Extremely fluid lavas

Loam

a soil with a texture in which none of the three soil grades (sand, silt, or clay) predominate over the others, generally best suited for supporting vegetation growth

Laterization

a soil-forming regime that occurs in humid tropical and subtropical climates as a result of high temperatures and abundant precipitation, soil-forming process of hot, wet climates. Oxisols, the typical end product of the process, are characterized by the presence of little or no humus, the removal of soluble and most fine soil components, and the heavy accumulation of iron and aluminum compounds, Despite the dense vegetation that is typical of these climate regions, little humus is incorporated into the soil because the plant litter decomposes so rapidly.

rock

a solid consolidated aggregate of various types of minerals or a consolidated aggregate of multiple individual pieces (grains) of the same kind of mineral, not one single, uniform crystal, Each constituent mineral in a rock remains separate and retains its own distinctive characteristics, properties of the rock as a whole are a composite of those of its various mineral constituents

Elastic solid

a solid that withstands stress with little deformation until a maximum value is reached, whereupon it breaks, materials are rigid and brittle, At the threshold value, elastic solids fail by fracturing

escarpment

a steep slope, or cliff, of any height regardless of the geomorphic or geologic process by which it formed, often shortened to scarp

plug dome

a steep-sided, explosive type of volcano with its central vent or vents plugged by the rapid congealing of its highly viscous, silica-rich lava, Where extremely viscous silica-rich magma pushes up into the vent of a volcanic cone but does not flow farther, Solidified outer portions of this blockage create the dome-shaped summit, and jagged blocks that break away from the plug, or preexisting parts of the cone, form the steep side slopes of the volcano, potential for extremely violent explosive eruptions, including pyroclastic flows

landforms

a terrain feature, such as a mountain, valley, and plateau, represent the interplay of one set of processes that elevate, depress, or disrupt Earth's surface, creating topographic inequalities, and another set of processes that wear down, fill in, and work to level the landscape, reflect the balance between endogenic and exogenic factors

polarity reversals

a time in geologic history when the south magnetic pole became the north magnetic pole and vice versa

dip-slip faults

a vertical fault where the movement is up and down the dip of the fault surface, Reverse and normal faults have dip-slip motion

clayey soil

a very fine-grained mineral particle, often the product of weathering, dominant size consists of clay particles; defined as having diameters of less than 0.002 millimeter, tiny, sheet-like particles that cannot be seen, retard water movement, becoming waterlogged and deficient in air

supervolcano

a volcanic center that has experienced an eruptive blast that emitted a volume of volcanic material greater than 1,000 cubic kilometers (240 cubic miles)

nonfoliated

absence of platy surfaces or wavy alignments of light and dark minerals that form during metamorphism

alluvium

accumulating sediment on river floodplains

deposition

accumulation of Earth materials at a new site after being moved by gravity, water, wind, or glacial ice

accretion

adding numerous chunks of crust to the main continent by collision, how Earth scientists consider continents to grow

Soil fertilization

adding nutrients to the soil to meet the conditions that certain plants require

Moisture conditions

affect the development and character of soils more directly than any other climatic factor, Extremely high rainfall will cause leaching of nutrients, and a relatively infertile soil. Extreme aridity may result in the absence of any soil development.

pyroclastic flows

airborne density current of hot gases and rock fragments unleashed by an explosive volcanic eruption, fast-moving density currents of airborne volcanic ash, hot gases, and steam that flow downslope close to the ground in a manner similar to some avalanches

Mass wasting

also called mass movement, is a collective term for the downslope transport of surface materials in direct response to gravity, Friction and rock strength are factors that resist this downslope movement of materials, Friction increases with the roughness and angularity of a rock fragment and the roughness of the surface on which it rests. Rock strength depends on physical and chemical properties of the rock and is reduced by any kind of break or gap in the rock, the steeper the slope angle—the easier it is for the gravitational forces to overcome the resistance provided by friction and rock strength

nonthermal spring

also known as a cold spring, is at or below the mean annual temperature of the atmosphere in the area of the spring

availability of groundwater

amount of precipitation that falls in the area and the amount that falls in adjacent regions that drain into it. A second important factor is the rate of evaporation. Third is the capacity of the ground to accept and transmit water to the subsurface through infiltration. A fourth factor involves the amount and type of vegetation cover, Two additional factors that affect the amount and availability of groundwater are the porosity and permeability of the sediments and rocks

modified Mercalli scale

an earthquake intensity scale with Roman numerals from I to XII used to assess spatial variations in the degree of impact on people and structures that a tremor generates

fissures

an extensive crack or break in rocks along which lava may be extruded, which is called a fissure flow, deep fractures in the crust can be independent of mountains or hills of volcanic origin

montmorillonite

an important component of moderately weathered soils, expands and contracts the most upon hydration and dehydration

unconformity

an interruption in the accumulation of different rock layers; often represents a period of erosion, Where markedly mismatching strata meet along an irregular, eroded surface, that contact between the rocks, indicates a gap in the section caused by removal of sediment from the top of one layer before deposition of the overlying sediment

stock

an irregular mass of intrusive igneous rock (pluton) smaller than a batholith, irregularly shaped intrusion, covers an area smaller than 100 square kilometers (40 sq mi)

principle of buoyancy

an object will float in a fluid as long as its total mass is less than that of the fluid it displaces, The difference in density (mass per unit volume) between the object and the fluid is represented by the proportion of the object that floats above the surface

plastic solid

any solid material that changes its shape under stress, and retains that deformed shape after the stress is relieved, movement within the plastic asthenosphere drives tectonic forces

What range of mean annual temperatures is most favorable for the accumulation of humus?

approximately 35-75 degrees F

five suborders of alfisols

aqualfs (seasonally wet and can be found in mesothermal areas such as Louisiana, Mississippi, and Florida), boralfs (found in moist, microthermal climates such as Montana, Wyoming, and Minnesota), udalfs (common in both microthermal and mesothermal climates that are moist enough to support agriculture without irrigation, such as Wisconsin, Ohio, and Tennessee), ustalfs (found in mesothermal climates that are intermittently dry, such as Texas and New Mexico), xeralfs (found in California's Mediterranean climate, which is characterized by wet winters and long, dry summers)

Volcanoes

are mountains or hills that form from the eruption of molten rock material from Earth's subsurface to the exterior

Wells

artificial opening that reaches the zone of saturation for the purpose of extracting groundwater, augments natural outflows of groundwater, artificial openings dug or drilled down to a point below the water table to extract groundwater

nonflowing artesian well

artificially dug outlet into which groundwater flows under its own pressure, but not reaching Earth's surface, If water in a well rises above the local water table but not to the point of flowing out of the well and onto the ground surface

bedrock collapse

associated with a growing underground cavern relatively near the ground surface, If continued solution makes the rock roof of the cavern thinner and thinner, eventually the rock can become so thin that it fails, crashing into the cavern void below

recumbent folds

asymmetrically folded rocks that have become overturned and so compressed that the fold lies horizontally

Tectonic forces

at the largest scale move the lithospheric plates, also cause bending, warping, folding, and fracturing of Earth's crust at continental, regional, and even local scales

NRCS soil classification system

based on the development and composition of soil horizons

geologic age of a rock

based on the time when it assumed its current state; melting, lithification, or metamorphism resets the age of origin

Soil development

begins when plants and animals colonize rocks or deposits of rock fragments

graben

block of crustal rocks between two parallel normal faults that has slid downward relative to adjacent blocks, Each block that slid downward between two normal faults, or that remained in place while blocks on either side slid upward along the faults, form basins, downdropped blocks

Soil Water

both an ingredient and a catalyst for chemical reactions that sustain life and influence soil development, adheres to soil particles and soil clumps by surface tension (the property that causes small water droplets to form rounded beads instead of spreading out in a thin film), also found as a very thin film, invisible to the naked eye that is bound to the surfaces of soil particles by strong electrical forces

bedding plane

boundary between different sedimentary layers that represent separate depositional events, denote a pause or some change in the nature of deposition, and the strata may differ in grain size, color, or composition

Bacteria

break down organic matter, humus, and the debris of living things into organic and inorganic components, allowing the formation of new organic compounds that promote plant growth

exogenic processes

break down rocks and erode rock fragments from sites of higher energy, transporting them to locations of lower energy, Rates of the exogenic processes depend on factors such as rock resistance to weathering and erosion, the amount of relief, and climate.

fault

breakage zone along which rock masses have slid past each other

normal faults

breakage zone with rocks on one side sliding down relative to rocks on the other side because of tensional forces; footwall up, hanging wall down, the direction of motion along a normal fault is opposite to that along a reverse or thrust fault

Chemical weathering

breakdown of rock material by chemical reactions that change the rock's mineral composition (decomposition), decomposes rock through chemical reactions that remove ions from the original rock-forming minerals

Physical weathering

breakdown of rocks into smaller fragments (disintegration) by physical forces without chemical change, also known as mechanical weathering, tends to be more pronounced where temperature and rainfall are low

freeze-thaw weathering

breaking apart of rock by the expansive force of water freezing in cracks; also called frost weathering or ice wedging

Soil Structure

can be influenced by external factors such as moisture regime and plant nutrient cycles interchanging chemicals with the soil, The absence of smaller particles typically hinders the development of a well-defined soil structure

Cones of depression

can develop in the water table as a result of pumping water from wells, In areas with many wells, adjacent cones of depression intersect, lowering the regional water table and causing shallow wells to go dry

perched water table

can develop where impermeable rock lies between a permeable layer and the regional water table, a minor zone of saturation overlying an aquiclude that exists above the regional water table, accumulation of groundwater above an aquiclude

tsunamis

caused by earthquakes that occur beneath or near the ocean, sets of large ocean waves generated by the sudden displacement of water

kaolinite

characteristic of highly weathered soils

Relief

characteristics of the land surface, such as the topography, the slope, and its aspect (the direction it faces),

oxidation

chemical union of oxygen atoms with another substance to create a new product, Metals, particularly iron and aluminum, are commonly oxidized in rock weathering and form iron and aluminum oxides as the new products

columns

column-shaped speleothem resulting from the joining of a stalactite and a stalagmite

silica

combination of oxygen and silicon, the two most abundant elements in Earth's crust

chemical constituents of a soil

come from multiple sources, including the breakdown (weathering) of underlying rocks, deposits of loose sediments, and minerals dissolved in water. Organic activities help to disintegrate rocks, create new chemical compounds, and release gases into the soil

Alkaline soils

common in the arid regions and in areas of limestone bedrock, can be made more productive by flushing the soil with irrigation water

terrestrial sandstones

commonly derive from sediments deposited in desert or floodplain environments on land

A horizon

commonly referred to as "topsoil," generally dark because it contains decomposed organic matter

Strike

compass direction of the line formed at the intersection of a tilted rock layer and a horizontal plane, used to describe the orientation of inclined rock layers

siltstone

composed of silt-sized particles, individual grains not easily visible with the unaided eye

Silicate minerals

compounds of oxygen and silicon that also include one or more metals and/or bases, created when molten rock matter containing these elements cools and solidifies, causing the crystallization of different minerals at successively lower temperatures and pressures, Dark, heavy, iron-rich silicate minerals crystallize first (at high temperatures), and light-colored, lower density, iron-poor minerals crystallize later at cooler temperatures, silicate minerals that crystallize later tending to be more stable and more resistant to breakdown

center of the planet

comprised of high-density iron and nickel, Earth's interior is primarily composed of solids, the densest of the three states of matter

Sandstone

consists of cemented sand-sized particles, most commonly grains of quartz. Sandstone is usually granular (has visible grains), porous, and resistant to weathering, but the cementing material influences its strength and hardness. If cemented by silica, sandstone tends to be more resistant to weathering than if it is cemented by calcium carbonate or iron oxide

Rocks

contain valuable resources, contribute to soil formation, are a major factor in determining Earth's surface elevation changes, and record various aspects of Earth's history, contain evidence of the environmental conditions that existed on Earth at the time and place of their formation

Rock salt

contains the mineral halite (NaCl), is quite susceptible to solution in water.

Water

contributes to weathering, which prepares rock matter for mass movement, adds weight to porous materials on a slope, decreases the strength of unconsolidated slope sediments, and can increase the slope angle

Coal

created by the accumulation and compaction of partially decayed vegetation in acidic, swampy environments where water-saturated ground prevents oxidation and complete decay of the organic matter. The initial transformation of such organic material produces peat, which, when subjected to deeper burial and further compaction, is lithified to produce coal. Most of the world's greatest coal deposits originated between 290 and 354 million years ago during the Mississippian and subsequent Pennsylvanian Periods of geologic time

transform faults

crosshatched plate boundaries along which lateral movement takes place, result when adjacent plates travel at variable rates, causing lateral movement of one plate relative to the other

horst

crustal block between two parallel normal faults that has slid upward relative to adjacent blocks, A fault block that moved relatively upward between two normal faults—that is, it actually moved up or it remained in place while adjacent blocks slid downward, form mountain ranges, upthrown blocks

basalt

dark-colored, mafic, fine-grained extrusive chemical and mineral equivalent of gabbro, a coarse-grained intrusive rock that cools at depth

soil

denotes a thin layer of predominantly fine-grained, unconsolidated surface material

hardpan

dense, compacted, clay-rich layer occasionally found in the subsoil (B horizon) that is an end product of excessive illuviation

density continuum (spectrum)

densest materials at Earth's center to the least dense substances at the outer edge of the atmosphere

avalanche

density current of pulverized (powdered) Earth material (including ice and snow) traveling rapidly downslope by the pull of gravity, a type of mass movement in which much of the involved material is pulverized—that is, broken into small, powdery fragments—and then flows rapidly as an airborne density current along Earth's surface, Avalanches of pulverized bedrock, called rock avalanches, and those of a very poorly sorted mixture of gravel, sands, silts, and clays, called debris avalanches, are also common and have caused considerable loss of life and destruction in mountain communities around the world

travertine or dripstone

deposit of calcium carbonate caused by dripping water

illuviation

deposition of fine soil components in the subsoil (B horizon) by gravitational water, As gravitational water percolates downward, it deposits the fine materials that were removed from the topsoil at a lower level in the soil, may eventually cause the subsoil to become dense and compact, forming a clay hardpan

Sedimentary Rocks

derived from sediment, that is, unconsolidated fragments that have accumulated together in a loose collection, one of three major rock categories; formed by compaction and cementation of rock fragments, organic remains, or chemical precipitates, After the fragments accumulate, often in horizontal layers, pressure from the addition of more material above compacts the sediment, expelling water and reducing pore space, Cementation occurs when silica, calcium carbonate, or iron oxide bonds the fragments together, three major categories of sedimentary rocks are clastic, organic, and chemical precipitate, become jointed, or fractured, when they are subjected to crustal stresses after they lithify

Punctuated equilibrium

describes Earth processes that operate slowly most of the time but are occasionally interrupted by events that cause major change in a landscape or natural system in a short time

Cleavage

describes how a mineral tends to break along preferred planes determined by its molecular structure

The Mercalli Scale of earthquake intensity (I-XII)

devised to measure a tremor's impact on people and the structures we have built

Debris flows and mudflows

differ from each other primarily in grain size and sediment attributes. Both flow faster than earthflows, often move down gullies or canyon stream channels for at least part of their travel, create raised channel rims called debris-flow or mudflow levees, and leave lobate (tongue-shaped) deposits where they spill out of the channel. They result from torrential rainfall or rapid snowmelt on steep, poorly vegetated slopes, and they are the most fluid of all mass movements

fault blocks

discrete block-like region of crustal rocks bordered on two opposite sides by normal faults

crystalline substance

displays a specific, repeated, three-dimensional structure at the molecular level

soluble minerals

dissolved chemicals held in solution, Most minerals found in soils are combinations of the common elements of surface rocks: silicon, aluminum, oxygen, and iron

strata

distinct layers of sediment accumulation

stratification

distinct layers within sedimentary rocks, called strata, Leaching and eluviation both strongly influence the characteristic layered changes with depth, Fine particles and substances dissolved from the upper soil are deposited in lower levels, which become dense and may be strongly colored by accumulated iron compounds

soil horizons

distinct soil layer characteristic of vertical zonation in soils; horizons are distinguished by their general appearances and their specific chemical and physical properties

Spreading centers

divergent plate boundaries that have new crustal material emerging along active rift zones, eventually pushing older rock progressively away from the boundary in both directions

artificial recharge

diverting surface water to permeable terrain for the purpose of replenishing groundwater supplies

30 inch annual precipitation isohyet

dividing line for distribution of alkaline and acidic soils in the United States

shield volcano

dome-shaped accumulation of multiple successive lava flows extruded from one or more vents or fissures, numerous successive basaltic lava flows that eventually pile up into the shape of a large mountain, resembles a giant knight's shield resting on Earth's surface, erupt extremely hot mafic lava, major feature of shield volcanoes is the outpouring of fluid basaltic lava flows, Compared with other volcano types, these eruptions are not very explosive, although they are still potentially dangerous and damaging

eluviation

downward removal of soil components by water

Most Common Elements in Earth's Crust

eight elements account for almost 99% of Earth's crust by weight, Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, and Magnesium, (the most common mineral groups are silicates, oxides, and carbonates)

basaltic plateaus

elevated, relatively flat-topped tablelands constructed from multiple layers of basalt flows

topographic variation

endogenic processes that create relief, exogenic processes that shape landforms and reduce relief, and the relative strength or resistance of different rock types to weathering and erosion

conical hills

erosional remnant hill in a limestone region with a shape similar to cones or haystacks

lava flows

erupted molten rock matter that oozed over the landscape and solidified, Layers of erupted rock matter that poured or oozed over the landscape when they were molten, can be made from any composition of lava, but basalt is by far the most common because its low viscosity and hot eruptive temperature allow gases to escape, greatly reducing the potential for an explosive eruption, Solidified lava flows tend to have many fractures, known as joints

Permeability

expresses the relative ease with which water flows through void spaces in Earth material, Despite the high porosity of clay sediments and shale, the pore spaces are poorly interconnected, giving them a low permeability, increases significantly if these materials have joints or fractures that provide interconnections to facilitate flow, The inherently high permeability of sands and gravels often offsets their low porosity to make them good sources from which to obtain water, presence of fractures is critical for providing permeability in many areas of igneous rocks, affects the rates and volumes of groundwater movement and is facilitated by the presence of large pore spaces, bedding planes, joints, faults, and even caverns

core

extremely hot and dense innermost portion of Earth's interior; the molten outer core is 2400 kilometers (1500 mi) thick; the solid inner core is 1120 kilometers (700 mi) thick, contains one third of Earth's mass, under enormous pressure, composed primarily of iron and nickel and consists of two distinct sections, the inner core and the outer core, the melting temperature of rock matter increases with pressure, and pressure increases with depth beneath Earth's surface

andesite

extrusive rock, intermediate composition

slides

fast mass wasting in which Earth material moves downslope in continuous contact with a discrete surface below, a cohesive or semi cohesive unit of Earth material slips downslope in continuous contact with the land surface, Debris slides, which contain a poorly sorted mixture of gravel and fine-grained sediment, and mudslides, which are dominated by wet silts and clays, are also common

Tensional tectonic forces

force originating within Earth that acts to pull two adjacent areas of rock away from each other (divergence), pull parts of the crust away from each other, pull in opposite directions in a way that stretches and thins the impacted part of the crust, commonly cause the crust to break into discrete blocks

Collapse sinkholes

form when the land surface caves into large subsurface voids created by solution of bedrock some distance beneath the surface, tend to have steep walls

joints

fracture or crack in rock, Joints caused by regional stresses in the crust are common features in any type of rock, including igneous rocks. Igneous rocks, however, also develop joints because molten rock shrinks in volume as it cools and solidifies, resulting in fractures, Structures such as bedding planes and joints are important in the development of physical landscapes because they are weak points in the rock that weathering and erosion can attack with relative eas

Subsurface water

general term for all water that lies beneath Earth's surface, including soil water and groundwater, includes water found in association with soil, sediments, and rock, arrives in the subsurface by means of precipitation from the atmosphere

Speleothem

generic term for any chemical precipitate feature deposited in caves, general term for any cavern feature made by secondary (later) precipitation of minerals from subsurface water, also referred to as cave decoration

crystals

geometric forms visible to the unaided eye and consisting of smooth faces and sharp edges, shape of a crystal is an expression of the mineral's molecular structure

soil creep

gradual downslope motion primarily affecting a relatively thin surface layer of weathered rock particles, Rates of soil creep are greater near the surface and diminish into the subsurface of a slope because the factors instigating it are more frequent near the surface and because frictional resistance to movement increases with depth

slow mass wasting

gravity-induced downslope movement of Earth material occurring so slowly that people cannot observe it directly

fast mass wasting

gravity-induced downslope movement of Earth material that people can witness directly

artesian wells

groundwater rises to a level above the local water table

slate

hard metamorphic rock, shale changes to this, cleaves along parallel planar surfaces that actually represent extremely thin foliation

Slope aspect

has a direct effect on microclimates and vegetative cover in areas outside of the equatorial tropics, North-facing slopes in the middle and high latitudes of the Northern Hemisphere have microclimates that are cooler and wetter than the warmer, drier south-facing exposures, which receive the sun's rays at a steeper angle

Mature Soils

have well-developed horizons that indicate the conditions under which they formed

Pacific Ring of Fire

high density of earthquakes and volcanoes around the margin of the Pacific Ocean

tower karst

high, steep-sided hills formed by solution of limestone or other soluble rocks in karst areas

cinder cone

hill composed of fragments of volcanic rock (pyroclastics) erupted from a central vent, smallest type of volcano, consist of predominantly gravel-sized pyroclastics, Each eruptive burst ejects more pyroclastics that fall and cascade down the sides to build an internally layered volcanic cone., typically have a rhyolitic composition but can be made of basalt if conditions of temperature and viscosity keep gases from escaping easily, form of a cinder cone is distinctive, with steep straight sides and a crater (depression) at the top of the hill,

transform movement

horizontal sliding of tectonic plates alongside and past each other, occurs where plates neither pull apart nor converge but instead slide past each other as they move in opposite directions, exists along the San Andreas Fault zone in California,

isoseismals

how the spatial variation in Mercalli intensity for a given earthquake is portrayed on map, lines connecting points of equal shaking and earthquake damage expressed in Mercalli intensity levels

flood basalts

huge amounts of basalt issued from some fissures

Folds are symmetrical

if the two limbs have approximately the same dip angle, which results from compressional forces that were relatively equal from both sides

dike

igneous intrusion with a wall-like shape, solidified magma in this case has a wall-like shape, When exposed by erosion of surrounding, less resistant rocks, dikes appear as vertical or near-vertical walls of rock rising above the surrounding topography

Laurasia

in the Northern Hemisphere, consisted of North America, Europe, and Asia

Gondwana

in the Southern Hemisphere, was made up of South America, Africa, Australia, Antarctica, and India

dip

inclination of a rock layer from the horizontal; always measured at right angles to the strike

Four Major Components of Soil

inorganic materials, soil water, soil air, and organic matter

Inorganic Materials

insoluble materials, soluble materials, minerals, chemicals

seismograph

instrument used to measure amplitude of passing seismic waves

International Ocean Discovery Program

international scientific partnership, will try to drill through the ocean floor where the distance to the Moho is only 5 to 6 kilometers (3 to 4 mi). Rock samples eventually retrieved from cores drilled through the Moho will add greatly to our understanding of the composition and structure of Earth's interior.

diorite

intrusive rock, intermediate composition

Chemical Weathering

ions from a rock are either released into water or recombine with other substances to form new materials, such as clay minerals, New materials made by chemical weathering are generally more stable at Earth's surface than the original rocks, The most important catalysts and reactive agents performing chemical weathering are water, oxygen, and carbon dioxide, all of which are common in soil, precipitation, surface water, groundwater, and air, chemical weathering increases as more water comes into contact with rocks, is particularly effective and rapid in humid climates, Most chemical reactions proceed faster at higher temperatures, In the tropical rainforest, savanna, and monsoon climates, chemical weathering is more significant than physical weathering, soils are deep, and landforms appear rounded

exogenic processes

land-forming process originating at or very near Earth's surface, tend to decrease relief, consist of various means of rock breakdown, collectively termed weathering, and the removal, movement, and relocation of those weathered rock products in the continuum of processes known, respectively, as erosion, transportation, and deposition

endogenic processes

landforming process originating within Earth, tend to increase the amount of surface relief, Tectonic and igneous processes

uvalas

large surface depression resulting from coalescing of sinkholes in karst areas, Sinkholes can grow in area and merge over time to form larger karst depressions, also called valley sinks

exfoliation dome

large, smooth, convex (dome-shaped) mass of exposed rock undergoing exfoliation due to weathering by unloading, an unloaded exfoliating outcrop of rock with a domelike surface form

tectonic forces

large-scale forces from inside Earth that break and deform the lithosphere, sometimes resulting in earthquakes and often responsible for mountain building, force originating within Earth that breaks and deforms Earth's crust

soil order

largest classification of soils based on development and composition of soil horizons

stratification

layering in rocks

landslide

layperson's term for any fast mass wasting; used by some earth scientists for massive slides that involve a variety of Earth materials, large, rapid mass wasting events that are difficult to classify because they contain elements of more than one category of motion or because multiple types of material—rock, debris, earth, soil, and mud—are involved in a single massive slide

midoceanic ridges

linear seismic mountain range that interconnects through the major oceans; it is where new molten crustal material rises through the oceanic crust, revealed spatial trends remarkably similar to those of the continental coastlines, rocks become progressively younger toward the midoceanic ridges, temperatures of rocks on the ocean floor vary significantly, being hottest near the midoceanic ridges and progressively cooler farther away

overthrust

low angle fault with rocks on one side pushed a considerable distance over those of the opposite side by compressional forces; the wedge of rocks that have overridden others in this way, the shallow displacement

mafic

lower in silica and rich in heavy minerals, such as compounds of magnesium and iron, type of chemical composition of igneous rocks

R horizon

lowest layer, unchanged parent material, either bedrock or transported deposits of rock fragments

Pyroclastic rocks

made of fragments ejected during a volcanic eruption

rift valleys

major lowland consisting of one or more crustal blocks down-faulted as a result of tensional tectonic forces, long and comparatively narrow zones of crust downdropped between normal faults

density

mass per unit volume, used to compare how equal amounts of various materials differ in mass

laccolith

massive igneous rock intrusion that bows overlying rock layers upwards in a domal fashion, a mushroom-shaped intrusion that develops where molten magma pushes its way between preexisting horizontal layers of other rock, causing the overlying strata to bulge upward as the intrusion grows

angle of repose

maximum angle at which a slope of loose sediment can stand without particles tumbling or sliding downslope, the steepest angle that a pile of loose material can maintain without rocks sliding or rolling downslope

Metamorphic Rocks

means "changed form.", Enormous heat and pressure deep in Earth's crust can alter (metamorphose) an existing rock into a new rock type that is completely different from the original by recrystallizing the minerals without creating molten rock matter, one of the three major categories of rock; formed by heat and pressure changing a pre-existing rock, typically harder and more compact, have a reoriented crystalline structure, and are more resistant to weathering when compared with the original rocks, two major categories of metamorphic rocks, foliated and nonfoliated

earthquake magnitude

measurement representing an earthquake's size in terms of energy released, developed by Charles F. Richter, expressed the size of earthquakes as recorded by a seismographs, a sensitive instruments that measure ground shaking, any whole number increase in earthquake magnitude (for example, from 6.0 to 7.0) represents a 10 times increase in amplitude on the seismograph trace

plankton

microscopic drifting organism

recrystallization

mineral grains or their constituent atoms and molecules are compacted and rearranged into a new form that is more stable at the higher temperature and pressure

mantle

moderately dense, relatively thick (2885 km/1800 mi) middle layer of Earth's interior that separates the crust from the outer core, representing nearly two thirds of Earth's mass, largest of Earth's interior zones, Seismic P and S waves both pass through the mantle, indicating that it is composed of solid rock matter, consists of silicate rocks (high in silicon and oxygen) that also contain significant amounts of iron and magnesium, Heat from decaying radioactive materials inside Earth drives the thermal convection currents that exist in much of the mantle

lava

molten rock material at the surface, molten (melted) rock matter erupted onto Earth's surface; solidifies into extrusive igneous (volcanic) rocks, the only form of molten rock matter that we can see

effusive eruptions

molten rock pours less violently onto the surface as flowing streams of lava

Mount St. Helens

most destructive eruption in U.S. history, blew gases and pyroclastic debris out laterally

Soil Characteristics

most important properties include color, texture, structure, acidity or alkalinity, and the capacity to hold and transmit water and air

transportation

movement of Earth materials from one site to another by gravity, water, wind, or glacial ice

plate divergence

movement of lithospheric plates away from each other, Tectonic forces that act to pull rock masses apart cause the crust to thin and weaken. Shallow earthquakes are often associated with this crustal stretching, and basaltic magma from the mantle wells up along crustal fractures. When oceanic crust is pulled apart, the process creates new ocean floor as the plates move away from each other along a spreading center, also called constructive plate margins, Most plate divergence occurs along oceanic ridges, but this process can also break apart continental crust, eventually reducing the size of the continents involved

plate convergence

movement of lithospheric plates toward each other and colliding, the incredible energy involved in convergence causes the crust to crumple as one plate overrides another, mark locations of major, and some of the tectonically more active, landforms on our planet, Deep trenches, volcanic activity, and mountain ranges can develop at convergent plate boundaries, depending on the type of crust involved in the plate collision, If one or both margins of a convergent plate boundary consist of oceanic crust, the margin of one plate—always one composed of oceanic crust—is forced deep below the surface in the process of subduction (The subducting plate is heated, and rocks are melted, as the edge of the plate plunges downward into the mantle)

seafloor spreading

movement of oceanic crust in opposite directions away from the midoceanic ridges, associated with the formation of new crust at the ridges and subduction of old crust at ocean margins, evidenced by the symmetrical pattern of increasing age with distance from the ridge and the symmetrical pattern of paleomagnetism measured in those rocks

tectonic processes

movements of parts of the crust and upper mantle, constitute the primary geomorphic mechanisms that increase the topographic irregularities on Earth's surface

slump-earthflow

moves as a cohesive unit along a concave surface in the middle and upper reaches of the failure, the slump part, Downslope of the failure plane, the mass continues to move but in the more fluid-like, less cohesive manner of an earthflow

volcanic ash

much like tiny slivers of glass. It is abrasive and causes respiratory problems in people and animals, clogging of air intakes for engines, destructive scratching and pitting of metal and glass, and the collapse of building roofs under the heavy weight of significant ash accumulations

pedosphere

name for separate system because soils integrate these major subsystems so well, characteristics of a soil reflect the atmospheric, hydrologic, lithologic, and biotic conditions under which it developed

geyser

natural eruptive outflow of water that alternates between hot water and steam, Where geothermal water flow is intermittent and somewhat eruptive, erupt when temperature and pressure of the water at depth reach critical levels, forcing a column of superheated water and steam out of the fissure in an explosive manner

artesian spring

natural flow of groundwater to the surface from below due to pressure, when water is under so much pressure that if it finds an outlet it will flow upward to a level above the local water table, conditions required for artesian water flow: First, a permeable aquifer, often sandstone or limestone, must be exposed at the surface in an upland area that receives high recharge by precipitation. The aquifer must receive water from the ground surface by infiltration, incline downward often hundreds of meters below the surface, and be confined between impermeable layers that prevent escape of the water except to the artesian springs. These conditions cause the aquifer to act as a pipe that conducts water through the subsurface

Springs

natural outflow of groundwater to the surface, where an aquifer intersects the ground surface and releases water that entered the water-bearing strata elsewhere at a higher elevation, commonly lie along fault zones or in other structural settings where a water-bearing permeable rock layer tilts downslope into a laterally adjacent impermeable rock layer, causing the water level to rise in the aquifer, commonly classified as nonthermal or thermal springs based on the temperature of the emerging groundwater

soil peds

naturally forming soil aggregate or clump with a distinctive shape that characterizes a soil's structure, particles clumped into masses, range from columns, prisms, and angular blocks to nutlike spheroids, laminated plates, crumbs, and granules, Although the peds may form a variety of shapes, some of the more common are granular (denoting a presence of sand) and platy (showing a presence of clay)

Rockfalls

nearly vertical drop of individual rocks or a rock mass through air pulled downward by the force of gravity, the most common type of fall, particularly common during the spring when snowmelt, rain and alternating freezing and thawing loosen and disturb rocks positioned on cliffs or steep slopes

thermal expansion and contraction

notion that rocks can weather due to expansion and contraction effects of alternating heating and cooling

Subduction zones

occur where two plates converge, with the margin of at least one of them consisting of oceanic crust. The plate with the denser oceanic crust is subducted beneath the less dense plate, whether it is continental or oceanic crust. Deep ocean trenches and either volcanic mountain ranges (continental crust) or island arcs (oceanic crust) lie along subduction zones

gleization

occurs in poorly drained areas under cold and wet environmental conditions, The resulting soils have a heavy surface layer of humus with a water-saturated clay horizon directly beneath

Podzolization

occurs mainly in the high midlatitudes where the climate is moist with short, cool summers and long, severe winters, soil-forming process of humid climates with long cold winter seasons. Spodosols, the typical end product of the process, are characterized by the surface accumulation of raw humus, strong acidity, and the leaching or eluviation of soluble bases and iron and aluminum compounds, coniferous forests, can take place outside its typical cold, moist climate regions if the parent material is highly acidic

Metamorphism

occurs most commonly where crustal rocks are subjected to great pressures by tectonic processes or deep burial, where rising magma generates heat that modifies the nearby rock, or where rocks are altered by both pressure and heat

regolith collapse (or cover collapse)

occurs where vertical gaps in the subsurface rock exist as a result of solution along joints or along other forms of weakness in the rock, most common after the water table subsequently falls below the subsurface gaps, such as during drought periods or by excessive pumping from wells, The drop in the water table leaves the regolith in a zone in which some pore spaces fill with air and through which water percolates downward toward the airfilled gap or cavern below

catastrophism

once-popular theory that Earth's landscapes developed in a relatively short time by cataclysmic events, largely rejected after about 1830

Limestone caverns

originate when subsurface water, sometimes flowing much like an underground stream, dissolves rock, leaving networks of passageways, Interaction between the cave air and mineral-saturated subsurface water percolating down to the cavern from above will then begin to precipitate minerals, especially calcium carbonate, on the cave ceiling, walls, and floor, decorating them with often-intricate depositional forms

rock "fins" of Arches National Park, Utah

owe their vertical, tabular shape to vertical joints in great beds of sandstone

caverns or caves

passageways above the zone of saturation, a system of connected passageways within the soluble bedrock, All caves formed by solution show some evidence of previous water flow, such as deposits of clay and silt on the cavern floor; in some caves water still actively flows, The majority of caverns develop just below the water table, where the rate of solution is most rapid, A subsequent lowering of the water table level, caused by the incision of surface streams, climate change, or tectonic uplift, fills the cavern with air, allowing calcium carbonate deposition to begin, much of the water that percolates into the cave from above first acquires carbon dioxide from the soil and then uses it to dissolve calcium carbonate (by carbonation) from the rocks and sediment it encounters on its way to the cave, degassing of carbon dioxide from the water essentially reverses the carbonation process, causing the water to precipitate calcium carbonate

weathering

physical (mechanical) fragmentation and chemical decomposition of rocks and minerals at and near Earth's surface, breakdown of rock material, A rock fragment broken (weathered) from a larger mass will be removed from that mass (eroded), moved (transported), and set down (deposited) in a new location, (weathering, erosion, transportation, and deposition actually represent a chain or continuum of processes that begins with the breakdown of rock), the principal source of the inorganic constituents of soil, without which most vegetation could not grow, Air pollution that contributes to the acidity of atmospheric moisture accelerates weathering rates

Unloading

physical weathering process whereby removal of overlying weight leads to rock expansion and breakage, erosional removal of overlying weight, Weathering by unloading is especially common on granite, but sometimes it affects other rocks that lack internal bedding and other planes of weakness

pyroclastic materials

pieces of volcanic rock, including cinders and ash, solidified from molten material erupted into the air, (fire fragments), also known as tephra, These rock fragments erupt in a range of sizes from volcanic ash, which is sand-sized or smaller, to cinders (2-4 mm), lapilli (4-64 mm), and blocks, include volcanic "bombs," large spindle-shaped clasts that solidified while flying through the air

vent

pipelike conduit for the eruption

Continental collision zones

places where two continental plates collide. Massive nonvolcanic mountains are built in those locations as the crust thickens because of compression

Biological Weathering

plant roots physically wedge into and expand cracks in rocks causing them to break further, Acids from decaying organic matter contribute to chemical weathering by solution, Lichens growing on rocks can physically dislodge particles and they also secrete acidic substances that mix with water from precipitation, encouraging chemical weathering by solution

epicenter

point on Earth's surface directly above the focus of an earthquake, where the strongest shock is normally felt

focus

point within Earth's crust or upper mantle where an earthquake originated, The subsurface location where rock displacement and the resulting earthquake originate, may be located anywhere from near the surface to a depth of 700 kilometers (435 mi)

foliated

presence of platy surfaces or wavy alignments of light and dark minerals that form during metamorphism.

Subduction

process associated with plate tectonic theory whereby an oceanic crustal plate is forced downward into the mantle beneath a lighter continental plate when the two converge, the process by which Earth material moves down to the subsurface in these zones

cryoturbation

process in which repeated cycles of freezing and thawing mix and churn the upper soil, Only the upper part of the soil undergoes freeze-thaw cycles. Permafrost does not permit soil water to percolate downward, so gelisol soils are typically water saturated when they are not frozen at the surface, occur in tundra and subarctic climate regions where soil development tends to be slow because chemical processes operate slowly in cold environments

lithify

process of compaction and cementation transform that turns sediments into solid, coherent layers of rock

soil-forming regimes

processes that create soils, The characteristics that make major soil types distinctive and different from one another, three primary soil-forming regimes: laterization, podzolization, and calcification

Shale

produced from the compaction of very fine-grained sediments, especially clays, often thinly layered with a smooth surface and a low permeability, easily cracked, broken apart, and eroded

Soil

provide nutrients that directly or indirectly support much of life on Earth, a dynamic body of natural materials capable of supporting a vegetative cover. It contains chemical solutions, gases, organic refuse, flora, and fauna, a dynamic, natural layer on Earth's surface that is a complex mixture of inorganic minerals, organic materials, microorganisms, water, and air, responds to climatic conditions (especially temperature and moisture), to the land surface configuration, to vegetative cover and composition, and to animal activity, been called "the skin of the Earth," a critical natural resource that functions as an open system

Compressional tectonic forces

pushing together from opposite sides (convergence), push crustal rocks together, How the affected rocks respond to compressional forces depends on how brittle (breakable) the rocks are and the speed with which the forces are applied, tend to shorten and thicken the crust

flows

rapid downslope movement of wet unconsolidated Earth material that experiences considerable mixing, masses of water-saturated unconsolidated sediments that move downslope because of the pull of gravity

mudflows

rapid mass wasting of wet, fine-grained sediment; may deposit levees and lobate (tongue-shaped) masses

Debris flows

rapid, gravity-induced downslope movement of wet, poorly sorted Earth material, flows transport more coarse-grained sediment than mudflows do, often originate on steep slopes, especially in arid or seasonally dry regions

Porosity

refers to the amount of space between the particles that make up the sediments or rocks, expressed as the volume of voids compared to the total volume of the material (including voids), Sediments and rocks consisting of clay-sized clasts, perhaps surprisingly, have a relatively high porosity and therefore can contain considerable amounts of water in the large number of very tiny pores, controls the potential amount of groundwater storage by providing available spaces for the water to be held

rock weathering

refers to the many natural processes that break rocks down into smaller fragments, All soils contain weathered rock fragments

fracture

refers to the nature of irregular breaks not along the preferred planes

igneous processes

related to the eruption and solidification of molten rock matter, constitute the primary geomorphic mechanisms that increase the topographic irregularities on Earth's surface

crust

relatively thin, approximately 8-64 kilometers (5-40 mi) deep, low-density surface layer of Earth, composed of a great variety of rock types that respond in diverse ways and at varying rates to surface processes, the only portion of the lithosphere of which Earth scientists have direct knowledge, yet it represents only about 1% of Earth's planetary mass, crust comprises the ocean floor and the continents, Two kinds of Earth crust, oceanic and continental, cold compared with the mantle and behaves in a more rigid and brittle fashion

leaching

removal by gravitational water of soluble inorganic soil components from the surface layers of the soil, Depleting nutrients in the soil by the through-flow of water, Leaching caused by high rainfall gradually replaces soil elements such as sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) with hydrogen

erosion

removal of Earth materials from a site by gravity, water, wind, or glacial ice

recharges

replenishing the amount of stored water, particularly in the subsurface

intermediate composition

represented by a rough balance between felsic and mafic minerals

parent material

residual (derived from bedrock directly beneath) or transported (by water, wind, or ice) mineral matter from which soil is formed, It is the development and action of organic matter through the life cycles of organisms and the climatic conditions that are primarily responsible for changing fragmented rocks or other parent materials into a soil, On a global basis, climate and the associated plant communities produce greater variations in soil characteristics compared with the influence of parent materials. Soil differences that are related to differences in parent material are most visible on a local level

Surface salinity

results from the upward capillary movement of water and evaporation at the surface causing deposits of salt

Obsidian or volcanic glass

results when molten lava cools too quickly for crystals to form, cools so rapidly that it is essentially a glass

felsic

rich in light-colored, lighter weight minerals, especially silicon and aluminum (fel for the mineral feldspar; si for silica), type of chemical composition of igneous rocks

weather

rock begins to break into smaller pieces (known as regolith) when exposed to the environmental conditions at Earth's surface

breccia

rock composed of lithified fragments that are angular rather than rounded

Organic sedimentary rocks

rock created from deposits of organic material, such as carbon from plants (coal), lithify from the remains of organisms, both plants and animals

chemical precipitate sedimentary rocks

rock created from dissolved minerals that have precipitated out of water, When the amounts of dissolved minerals in ocean or lake water reach saturation they begin to precipitate and build up as a deposit on the sea or lake bottom, Some fine-grained limestone rocks form in this manner from chemical precipitates of calcium carbonate

insoluble materials

rock fragments and minerals that will not readily dissolve in water

residual parent material

rock fragments that form a soil and have accumulated in place through weathering

transported parent material

rock fragments that form a soil and originated elsewhere and then were transported and deposited in the new location

aquifer

rock layer that is a container and transmitter of groundwater; it is both porous and permeable, most aquifers that supply water for human use are sandstones, limestones, or deposits of loose, coarse sediment (sand and gravel)

aquiclude

rock layer that restricts flow and storage of groundwater; it is impermeable and nonporous, such as shale or slate

differential weathering and erosion

rock types vary in resistance to weathering and erosion, causing the processes to occur at different rates and often producing distinctive landform features, topographic effects of differential weathering and erosion tend to be more prominent and obvious in landscapes of arid and semiarid climates

hydration

rock weathering due to substances in cracks swelling and shrinking with the addition and removal of water molecules, water molecules attach to the crystalline structure of a mineral without causing a permanent change in that mineral's composition, when hydrating materials expand in cracks or voids within rocks, pieces of the rock can wedge apart

coarse-grained

rocks with large minerals that are visible without magnification

sinkholes

roughly circular surface depression related to the solution of rock in karst areas, also called dolines, which are prominent features of many karst landscapes, The two processes, solution and collapse, actually cooperate to create most sinkholes in soluble rocks, rapid formation of sinkholes may result from excessive groundwater withdrawal for human use or from significant drought periods

spheroidal weathering

rounded shape of rocks often caused by preferential weathering along joints of cross-jointed rocks, develops especially well on jointed crystalline rocks, such as granite, is not a specific weathering process; it is a form that some rocks acquire as a result of weathering

pH scale

scale from 0 to 14 that describes the acidity or alkalinity of a substance and that is based on a measurement of hydrogen ions; pH values below 7 indicate acidic conditions; pH values above 7 indicate alkaline conditions, indicates the concentration of reactive hydrogen ions present, The pH scale is logarithmic, meaning that each change in a whole pH number represents a tenfold change, also an inverted scale—a lower pH means a greater amount of hydrogen ions (higher acidity). Low pH values indicate an acidic soil, and high pH indicates alkaline conditions, Most complex plants will grow only in soils with levels between pH 4 and pH 10, although the optimum pH for vegetation growth varies with the plant species, between pH 5 and pH 7 is a common range for humid region soils; and between pH 7 and pH 9 for soils in arid regions.

Sandy soil

sediment particles ranging in size from about 0.05 millimeter to 2.0 millimeters, mostly sand-sized particles, Rocks larger than 2.0 millimeters (less than 1 in.) are regarded as pebbles, gravel, or rock fragments and technically are not considered to be soil particles.

silty soil

sediment particles with a grain size between 0.002 millimeter and 0.05 millimeter, dominant silt particles

Geomorphologists

seek explanations for the origin, shape, and spatial distribution of terrain features of all kinds and for the processes that modify and destroy them

microplate terranes

segments of crust, have their own distinct geology from that of the continent to which they are now joined, may have originally been offshore island arcs, undersea volcanoes, or islands made of continental fragments, added to continents through subduction processes

Earthquakes

series of shock waves set in motion by sudden movement along a fault, evidence of present-day tectonic activity, are ground motions of Earth caused when accumulating tectonic stress is relieved by the sudden displacement of rocks along a fault, The abrupt, lurching movement of crustal blocks past one another to new positions releases energy that moves through Earth as traveling seismic waves

capillary water

serves as a stored water supply for plants, soil water that clings to soil peds and individual soil particles as a result of surface tension. Capillary water moves in all directions through the soil from areas of surplus water to areas of deficit, can move in all directions through soil because it migrates from areas with more water to areas with less, during dry periods, when there is no gravitational water flowing through the soil, capillary water can move upward or horizontally to supply plant roots with moisture and dissolved nutrients.

Declination

shows the direction to the magnetic pole, The information provided by these paleodeclinations is the orientation of ancient landmasses

talus

slope (sometimes cone-shaped) of angular, broken rocks at the base of a cliff deposited by rockfall, sometimes referred to as a talus slope or, where cone-shaped, a talus cone

creep

slow downslope movement of Earth material involving the lifting and falling action of sediment particles, Most hillslopes covered with weathered rock or soil undergo this, the most widespread and persistent form of mass wasting because it affects nearly all slopes that have soil or weathered rock fragments at the surface

solifluction

slow movement of saturated soil downslope by the pull of gravity; especially common in permafrost areas, literally means "soil flow," refers to the slow downslope movement of water-saturated soil or regolith, Solifluction is most common in high-latitude or high-elevation tundra regions that have permafrost, a subsurface layer of permanently frozen ground

spatter cone

small volcanic hill, ejects molten lava much like a miniature volcano

colloidal

smaller than 0.0001 millimeter, Having colloidal-sized materials in the soil benefits soil fertility because colloids increase the cation exchange capacity of the soil, which is essentially the ability of the soil to hold plant nutrients

Mollisols

soil that develops in grassland regions, are among the best soils for sustained agriculture, Because they are located in semiarid climates, mollisols are not heavily leached and they have a generous supply of bases, especially calcium, thick, dark-colored surface layer rich in organic matter from the decay of abundant root material

Histosols

soil that develops in poorly drained areas, such as swamps, meadows, or bogs, as a product of gleization, largely composed of decomposing plant material, waterlogged soil conditions deprive bacteria of the oxygen necessary to decompose the organic matter, most common in tundra areas or in recently glaciated, high-latitude locations such as Scandinavia, Canada, Ireland, and Scotland, primary source of peat, which is a fuel source in some regions, and also is used in landscaping

Spodosols

soil that develops in porous substrates such as glacial drift or beach sand, most closely associated with the podzolization soil-forming process, strong horizon development, There is often a white or light-gray E horizon (albic horizon) covered with a thin, black layer of partially decomposed humus and underlain by a colorful B horizon enriched in relocated iron and aluminum compounds (spodic horizon), low in bases

Vertisols

soil that develops in regions with strong seasonality of precipitation such as the tropical wet and dry climates, most common where the parent materials produce clay-rich soils, constant shrink-swell process disrupts horizon formation to the point that soil scientists often describe vertisols as "self-plowing" soils, Vertical soil movement may damage highways, sidewalks, foundations, and basements that are built on shrink-swell soils, dark-colored, are high in bases, and contain considerable organic material derived from the grasslands or savanna vegetation with which they are normally associated, can be agriculturally productive

Andisols

soil that develops on volcanic parent material, usually volcanic ash, the dust-sized particles emitted by volcanoes, Because many of these soils are replenished by eruptions, they are often fertile

Oxisols

soil that develops over a long period of time in tropical regions with high temperatures and heavy annual rainfall, are almost entirely leached of soluble bases and are characterized by a thick development of iron and aluminum oxides, soil consists mainly of minerals that resist weathering (for example, quartz, clays, and hydrated oxides), most closely associated with the humid tropics, but they also extend into savanna and tropical thorn forest regions

Gelisols

soil that experiences frequent freezing and thawing, above permafrost, permanently frozen subsoil

Ultisols

soil that has a subsurface clay horizon, is low in bases, and is often red or yellow in color, are low in bases because they develop in moist or wet regions, characterized by a subsurface clay horizon (argillic horizon) and are often yellow or red because of residual iron and aluminum oxides in the A horizon, most closely associated with the southeastern United States, Ultisols remain productive only with the continuous application of fertilizers.

Alfisols

soil that has a subsurface clay horizon, is medium to high in bases, and is light colored, occur in a wide variety of climate settings, characterized by a subsurface clay horizon (argillic B horizon), a medium to high base supply, and a light-colored ochric epipedon, Because of their abundant bases, alfisols can be very productive agriculturally if local deficiencies are corrected: irrigation for the dry suborders and properly drained fields for the wet suborders

Entisols

soil with little or no development, lack horizons because they have only recently begun to form, often associated with the continuing erosion of sloping land in mountainous regions or with the frequent deposition of alluvium by flooding or in areas of windblown sand

salinization

soil-forming process of low-lying areas in desert regions; the resulting soils are characterized by a high concentration of soluble salts as a result of the evaporation of surface water, concentration of salts in the soil, is often detrimental to plant growth, poor drainage, occurs in stream valleys, interior basins, and other low-lying areas, particularly in arid regions with high groundwater tables

calcification

soil-forming process of subhumid and semiarid climates. Soil types in the mollisol order, the typical end products of the process, are characterized by little leaching or eluviation and by the accumulation of both humus and mineral bases (especially calcium carbonate), occurs in regions where evapotranspiration significantly exceeds precipitation, important in the climate regions where moisture penetration is shallow, shrubs or shallow-rooted grass are the primary forms of vegetation, Grasses and their dense root networks provide large amounts of organic matter, which is mixed deep into the soil by burrowing animals, Middle-latitude grassland soils are rich in bases and in humus and are the world's most productive agricultural soils, a soil development process that is most prominent in cool to hot subhumid or semiarid climate regions, particularly in grassland regions but also in deserts

Aridisols

soils of desert regions that develop primarily under conditions where precipitation is much less than half of potential evaporation, most aridisols reflect the calcification process, where groundwater tables are high, evidence of salinization may also be present, Although aridisols tend to have weak horizon development because of limited water movement in the soil, there is often a subsurface accumulation of calcium carbonate (calcic horizon), salt (salic horizon), or calcium sulfate (gypsic horizon). Soil humus is minimal because vegetation is sparse in deserts; therefore, aridisols are often light in color, usually alkaline, can support productive agriculture if irrigated to reduce the pH and salinity, most common soils on Earth

Dark Brown or Black Soil Color

soils rich in humus, tend to be very fertile, often referred to as rich

bedrock

solid rock of Earth's crust that underlies soil and other unconsolidated materials, A mass of consolidated rock that has not been weathered, whether exposed at the surface or buried, often lies buried under regolith or under rock fragments deposited by other surface processes, such as stream flow or gravity

Luster

specifies the shininess of a mineral

stalactites

spire-shaped speleothem that hangs from the ceiling of a cavern

stalagmites

spire-shaped speleothem that rises up from a cavern floor, created by water saturated with calcium carbonate dripping onto the floor of a cavern

disappearing streams

stream that has its flow diverted entirely to the subsurface

paleogeography

study of the past geographical distribution of environments, tries to reconstruct the past environment of a geographic region based on geologic and climatic evidence

intermediate zone

subsurface water layer between the zone of aeration above and the zone of saturation below; saturated only during times of ample precipitation, The water table fluctuates through this middle layer, which alternates between unsaturated and saturated conditions

percolation

subsurface water moving downward to lower zones by the pull of gravity

zone of saturation

subsurface water zone in which all voids in rock and soil are filled with water; the top of this zone is the water table

exfoliation

successive removal of outer rock sheets or slabs broken from the main rock mass by weathering, each concentric broken layer of rock is an exfoliation sheet

epipedons

surface layers that usually exhibit dark shading associated with organic material (humus), surface soil layer that possesses specific characteristics essential to the identification of soils in the National Resources Conservation Service System

water mining

taking more groundwater out of an aquifer through pumping than is being replaced by natural processes in the same period of time

origin of continents

tend to have a core area of very old igneous and metamorphic rocks that are interpreted as representing the deeply eroded roots of ancient mountains

cleave

tendency to break apart

pyroclastics

term for the accumulation of fragments of volcanic rock, dust-sized or larger that settle out of the air as a result of very explosive eruptions of molten rock material, also known as tephra

porosity

the amount of space that may contain fluids, characteristic of soil or bedrock that relates to the amount of pore space between individual peds or soil and rock particles and that determines the water storage capacity of Earth material

continental shields

the ancient part of a continent that consists of crystalline rock, history of tectonic stability over an immense period of time

topography

the arrangement of high and low elevations in a landscape

Folding

the bending or wrinkling of Earth's crust due to compressional tectonic forces, occurs when compressional forces are applied to rocks that are ductile (bendable) rather than brittle, rocks deep within the crust typically fold rather than break in response to compressional forces, more likely than fracturing when the compressional forces are applied slowly, Eventually if the stress is great enough, the rocks can break, with one section pushed up over another

biological weathering

the breakdown of rocks related to vegetational processes or animal activities, Disintegration and decomposition of rock matter accomplished in ways influenced by organisms

Minerals

the building blocks of rocks, an inorganic, naturally occurring, crystalline substance represented by a specific chemical formula and crystalline structure, Minerals with weak internal bonds undergo chemical alteration most easily.

soil taxonomy

the classification and naming of soils

effluent

the condition of groundwater seeping into a stream, keeps the stream flowing between rains or during dry seasons

influent

the condition of stream water seeping into the channel bed and adding to groundwater, dry periods in which the streams lose water by seepage into the ground below

plate tectonics

the continual movement of segments of Earth's surface over millions of years

Soil texture

the distribution of particle sizes in a soil that give it a distinctive "feel," refers to the particle sizes (or distribution of sizes) that make up a soil, determined by sieving the soil to determine the percentage of particles falling into the size ranges for clay, silt, and sand, helps determine a soil's capacity to retain moisture and air that are necessary for plant growth

synclines

the downfolded element of folded rock structure

volcanism

the eruption of molten rock matter onto Earth's surface, the eruption of molten rock material from Earth's subsurface to the exterior, increase surface relief

lithosphere

the extensive part of the Earth system that lies beneath our feet, the solid, or rock, portion of Earth, The crust and the uppermost part of the mantle, which is rigid like the crust, make up the lithosphere, brittle outer shell of Earth, including the crust and the rigid, uppermost mantle layer

massive

the fewer joints and bedding planes a rock has, more resistant to weathering

stress

the force per unit area

continental collision

the fusing together of landmasses as tectonic plates converge, Continental crust converging with continental crust, closes an ocean basin that once separated the colliding landmasses, and therefore it has also been called continental suturing, The crustal thickening that occurs along this type of plate boundary generally produces major mountain ranges resulting from massive folding and crustal block movement rather than volcanic activity

paleomagnetism

the historic record of changes in Earth's magnetic field, Iron-bearing minerals in rock record the magnetic field of Earth as it existed when the rock solidified, helped initiate this reassessment of Wegener's theory, revealed that the polarity of Earth's magnetic field has reversed many times in the past, the study of magnetic fields in mineral crystals within rocks of varying ages, Basaltic rocks, which are iron rich, are most commonly used, Three important characteristics that these rocks record are polarity (normal, like that of today, or reversed), declination, and inclination, which is measured with a vertically mounted compass needle

continental drift

the idea that continents and other landmasses have shifted their positions during Earth's history, theory proposed by Alfred Wegener stating that the continents joined, broke apart, and moved on Earth's surface; it was later replaced by the theory of plate tectonics

geothermal gradient

the idea that temperature increases with increasing depth inside Earth

regolith

the inorganic portion of soils

gabbro

the intrusive compositional equivalent of basalt, which is an extrusive igneous rock

silicates

the largest and most common mineral group, constituting 92% of Earth's crust

Continental crust

the less dense thicker portion of Earth's crust; underlies the continents, comprises the major landmasses on Earth that are exposed to the atmosphere, the average density of continental crust is less than that of oceanic crust, considerably thicker than oceanic crust, contains more light-colored rocks than oceanic crust does and can be regarded as granitic in composition

water table

the level below which all available spaces are filled with water

moment magnitude

the measure of an earthquake's size in terms of energy released, each earthquake has only one moment magnitude representing the earthquake's size in terms of energy released

Convection

the mechanism for plate tectonics, Heat causes convection currents of material in the mantle to rise toward the base of the solid lithosphere, where the flow becomes more horizontal. As the asthenosphere undergoes its slow, lateral flow, the overlying lithospheric plates are carried along because of friction at the boundary between the asthenosphere and lithosphere

microorganisms

the microscopic plants and animals that live in a soil, bacteria are perhaps the most important microorganisms that live in soils

Plate tectonics

the modern, comprehensive theory that explains seafloor spreading, subduction, and the horizontal movement of lithospheric plates, theory that superseded continental drift and is based on the idea that the lithosphere is composed of a number of segments or plates that move independently of one another, at varying speeds, over Earth's surface, (thermal convection currents in Earth's mantle cause the deformable, plastic asthenosphere, near the top of the mantle, to flow. As material in the asthenosphere flows horizontally, it carries along the overlying rigid and brittle lithosphere, causing it to break into lithospheric plates), The huge thermal convection cells driving plate tectonics consist of hot mantle material traveling upward toward Earth's surface and cooler material returning downward deeper into the mantle, Where rising mantle material in the convection cells reaches the asthenosphere, it spreads laterally and flows plastically in opposite directions (diverges), pulling apart the rigid overlying lithosphere. This opens a midoceanic ridge, which marks the boundary between two separate plates

foliation

the occurrence of banding or platy structure in metamorphic rocks, With enough heat and pressure, metamorphism causes minerals to recrystallize perpendicular to the applied stress, forming platy (elongated) flat surfaces or wavy bands (requires greater pressure than platy surface), Preexisting rocks composed of one dominant mineral do not develop foliation when metamorphosed

rock structure

the orientation, inclination, and arrangement of rock layers in Earth's crust, Sedimentary rocks are particularly useful for identifying tectonic deformation because most are originally horizontal, with each successive, overlying rock layer younger than the one beneath it. If strata are bent, fractured, offset, or otherwise out of sequence, some kind of structural deformation has occurred, reflects endogenic factors

infiltration

the process of water seeping downward into the soil or other surface materials, water moves from the ground surface into void spaces in soil and loose sediments, as well as into cracks, joints, and other fractures in rock, replenishes water in subsurface

Plutonism

the processes associated with the formation of rocks from magma cooling deep beneath Earth's surface, refers to the slow, subsurface cooling of magma into various types of intrusive igneous rock masses, increase surface relief

permeability

the rate at which water can pass through, characteristic of soil or bedrock that determines the ease with which water moves through Earth material, usually greatest in sandy soils and poorest in clayey soils

speleology

the scientific study of caverns

subsidence

the sinking of an air parcel to a lower altitude, or the sinking or lowering of a land surface, a sinking of the land where high groundwater demand has led to extensive pumping

swallow hole

the site where a surface stream is diverted to the subsurface, such as into a cavern system, In some cases these underground-flowing "lost rivers" reemerge at the surface as springs where they encounter impervious beds below the limestone

severity of an earthquake

the size of the event as a physical Earth process, and the degree of its impact on people

Faulting

the slippage or displacement of rocks along a fracture surface

inner core

the solid, innermost portion of Earth's core, probably of iron and nickel, that forms the center of Earth, has a radius of about 960 kilometers (600 mi), solid with a very high material density

fault scarp

the steep cliff or exposed face of a fault where one crustal block has been displaced vertically relative to another, A cliff that results from movement along a fault

geomorphology

the study of the origin and development of landforms, a major subfield of physical geography devoted to the scientific study of landforms

Isostasy

the term for equalization of hydrostatic pressure (fluid balance) between the lithosphere and asthenosphere, suggests that a column of lithosphere (and the overlying hydrosphere) anywhere on Earth weighs about the same as a column of equal diameter from anywhere else, regardless of vertical thickness, suggests that mountains are made of relatively low-density crustal materials and thus exist in areas of very thick crust, whereas regions of low elevation have thin, high-density crust

Oceanic crust

the thinner and denser, basaltic portion of Earth's crust; underlies the ocean basins, composed of basalt (basaltic rocks are the most common rocks on Earth), a heavy, dark-colored, iron-rich rock that is also high in silicon (Si) and magnesium (Mg)

anticlines

the upfolded element of folded rock structure

outer core

the upper portion of Earth's core; considered to be composed of molten iron liquefied by Earth's internal heat, Because the outer core blocks the passage of seismic S waves by reflecting them, but allows continuation of refracted P waves, Earth scientists know that the outer core is molten, that is, it consists of liquid (melted) rock matter.

active layer

the upper soil zone that thaws in summer in regions underlain by permafrost, freezes during winter but thaws during summer

Contour farming

the use of buffer zones between fields and along water courses, are excellent examples of soil conservation methods

C horizon

the weathered parent material from which the soil has developed—either fragments of the bedrock, or deposits of rock materials that were transported to the site by water, wind, glacial, or other surface processes

erosion

the world loses between 5 and 7 million hectares (12.36 and 17.30 million acres) of farmland every year

laterite

these soils are generally reddish in color from iron oxides; the term laterite means "brick-like.", iron-, aluminum-, and manganese-rich layer in the subsoil (B horizon) that can be an end product of laterization in the wet-dry tropics (tropical savanna climate), do not have an O horizon, and the A horizon loses fine soil particles and most minerals and bases except for iron and aluminum compounds, which are insoluble primarily because of the absence of organic acids, the topsoil is reddish, is coarse textured, and tends to be porous, In contrast to the A horizon, the B horizon in a lateritic soil has a heavy concentration of illuviated materials. rapid cycling of nutrients, only moderately acidic

Slumps

thick unit of unconsolidated fine-grained material sliding downslope on a concave, curved slip plane, rotational slides where earth—a thick block of fine-grained material—moves along a concave, curved surface

earth

thick unit of unconsolidated, predominantly fine-grained slope material, often tens of meters thick

asthenosphere

thick, plastic layer within Earth's mantle that flows in response to convection, instigating plate tectonic motion, Beneath the lithosphere, thick layer of the upper mantle that responds to stress by deforming and flowing slowly rather than by fracturing, Movement in the asthenosphere, in turn, is produced by thermal convection currents originating deeper in the mantle below the asthenosphere. These currents are driven by heat from decaying radioactive materials in the planet's interior

rock types

three major categories of rocks based on mode of formation: igneous, sedimentary, and metamorphic

seismic waves

traveling wave of energy released during an earthquake or other shock, most important evidence that scientists have used to gain indirect knowledge of Earth's interior

Illite and vermiculite

two clay minerals associated with slightly weathered soils

falls

type of fast mass wasting characterized by Earth material plummeting downward freely through air

S (secondary) waves

type of seismic wave produced by an earthquake, travel more slowly than P waves, thus they arrive at the seismograph later, can only move through solids; they do not travel through fluids, whether liquid or gas

P (primary) waves

type of seismic wave produced by an earthquake, waves travel faster and are the first to arrive at a recording seismograph, pass through all types of matter, including liquids and gases, responsible for the rumbling sound that we hear during an earthquake

cross bedding

type of stratification, thin layers within sedimentary rocks that were deposited at an angle to the dominant rock layering, characterized by multiple thin sediment layers that accumulated in inclined, rather than horizontal, beds, The compass direction toward which cross beds tilt often reflects the travel direction of the medium that deposited the cross-bedded sediment, whether waves along a coast, currents in streams, or winds over sand dunes

Gley soils

typically associated with peat bogs where the soil has an accumulation of humus overlying a blue-gray layer of thick, gummy, water-saturated clay

limestone

typically contains fossil shell and coral fragments, Rich in calcium carbonate, organic sedimentary rock, may vary from a jagged and cemented complex of visible shells or fossil skeletal material (an organic sedimentary rock) to a chemical precipitate sedimentary rock with a smooth surface, tends to be a weak rock in humid environments, but in arid or semiarid climates it tends to be resistant, can slowly dissolve in water

Molten basalt

typically erupts at very high temperatures, flows easily, and cools rapidly into a fine-grained extrusive igneous rock

Marine sandstones

typically form from sediments deposited in a nearshore coastal zone

Young or "immature" soils

typically have poorly developed, or perhaps no horizons at all

Red or yellow soils

typically indicate the presence of iron

Acid mine drainage

typically occurs when subsurface water flowing through mines or mine tailings undergoes chemical reactions that leave the water highly acidic (low pH) and metal rich, a serious environmental concern in some coal- and metal-mining regions, Mines that lie in the zone of the fluctuating water table between the soil water zone and the zone of saturation, like many mines in the Appalachian coal fields, are particularly susceptible to acid mine drainage because of the frequent introduction of new, moving, oxygenated water

Debris

unconsolidated slope material with a wide range of grain sizes including at least 20% gravel

karst

unique landforms and landscapes derived by the solution of soluble rocks, particularly limestone, A warm, humid climate with ample precipitation is most conducive to karst development, Compared with colder humid climates, warmer humid climates have greater amounts of vegetation, which supplies carbon dioxide to subsurface water. Carbon dioxide is necessary for carbonation of limestone and it increases the acidity of water, which encourages solution in general, Another important factor in the development of karst landforms is movement of subsurface water, After intense and long-term karst development, especially in wet tropical conditions, only limestone remnants are left standing above insoluble rock below

water table

upper limit of the zone of saturation below which all pore spaces are filled with water, does not remain at a fixed depth below the land surface, but in any given area it fluctuates with the quantity of recent precipitation, loss by outflow to the surface, and the amount of removal by pumping

zone of aeration

uppermost layer of subsurface water where pore spaces typically contain both air and water, found under conditions of moderate precipitation and good drainage, rarely becomes saturated

halite

used as table salt, has the specific chemical formula NaCl and, as a crystal, adopts a cubic form

Red Soil

usually indicates that oxidation has been an active process—oxygen has chemically reacted with the soil minerals. Red also indicates that iron is in the soil. Just like rusting iron, many iron-rich minerals turn red when oxidized. The formula for this process is (ferrous oxide + oxygen becomes hematite, a reddish iron oxide).

Fast Mass Wasting

usually leave a visible upslope scar on the landscape, revealing where material has been removed, and a definite deposit where transported Earth material has come to rest at a lower elevation

heaving

various means by which particles are lifted perpendicular to a sloping surface, then fall straight down by gravity

soil profile

vertical cross-section of a soil that displays the various horizons or soil layers that characterize it; used for classification, vertical cross-section of a soil from the surface down to the parent material

volcanic neck

vertical igneous intrusion that solidified in the vent of a volcano, ex. Shiprock, NM, a resistant remnant of rock that in molten form pushed into the pipe of a volcano

Explosive eruptions

violently blast pieces of molten and solid rock into the air

composite cone

volcano formed from alternating layers of lava and pyroclastic materials; generally known for violent eruptions, results when formative eruptions are sometimes effusive and sometimes explosive, composed of a combination—that is, they represent a composite—of lava flows and pyroclastic materials, also known as stratovolcanoes because they are constructed of layers (strata) of pyroclastics and lava, form from andesite, which is a volcanic rock intermediate in silica content and explosiveness between basalt and rhyolite, As a composite cone grows larger, the vent eventually becomes plugged with unerupted andesitic rock, composed of lava flows as well as pyroclastic material and have distinctive concave side slopes, Most of the world's best-known volcanoes are composite cones

base flow

water from the zone of saturation seeps directly into the channel beneath the stream's water surface

geothermal water

water heated by contact with hot rocks in the subsurface, Hot springs form where geothermal waters flow out onto Earth's surface fairly continuously, usually associated with areas of tectonic and volcanic activity, especially along lithospheric plate boundaries and over hot spots

groundwater

water in the saturated zone below the water table

hygroscopic water

water in the soil that adheres to mineral particles, does not move through the soil, nor does it supply plants with the moisture they need

soil water

water in the zone of aeration, the uppermost subsurface water layer

hydrolysis

water molecules chemically recombining with other substances to form new compounds, water molecules alone, rather than oxygen or carbon dioxide in water, react with chemical components of rock-forming minerals to create new compounds, Hydrolysis of silicate minerals often produces clay minerals, some of which swell and shrink considerably when hydrated and dehydrated, and thereby contribute to physical weathering by hydration, chemical weathering by hydrolysis, however, that produces many of the clay minerals

infiltrate

water seeping downward into the soil or other surface materials

salt crystal growth

weathering by the expansive force of salts growing in cracks in rocks; common in arid and coastal regions, leads to granular disintegration in coarse crystalline (intrusive igneous) rocks and to the removal of clastic particles from sedimentary rocks, especially sandstones

granular disintegration

weathering feature of coarse crystalline rocks in which visible individual mineral grains fall away from the main rock mass, differential thermal expansion and contraction of individual mineral grains in coarse crystalline rocks contributes to it

Mud

wet, fine-grained sediment, particularly clay and silt sizes, indicates saturated sediment composed mainly of clay and silt, which are the smallest particle sizes

Lime (calcium carbonate)

when deposited by evaporating soil water can build up to produce a cement-like layer, called caliche, which like a clay hardpan prevents the downward percolation of water.

loess

when dust settles out of the atmosphere to form blankets of wind-deposited silts

Transform plate boundaries

where shearing forces and lateral sliding occurs, also experience many earthquakes, Volcanic activity along transform plate boundaries ranges from moderate on the seafloor to slight in continental locations.

uniformitarianism

widely accepted theory that Earth's geological processes operate today as they have in the past, the idea that internal and external Earth processes operated in the geologic past not by cataclysms unparalleled in recent centuries, but slowly as they do today

Mineral salts

will precipitate to form a variety of sedimentary deposits that are useful to humans, These include gypsum (used in wallboard), halite (common salt), and borates, which are important in hundreds of products such as fertilizer, fiberglass, detergents, and pharmaceuticals

The extreme uppermost part of the mantle

with a thickness of about 100 kilometers (60 mi), has a chemical composition like the rest of the mantle, but it responds to applied stress like the overlying Earth layer, the crust. The response is that of an elastic solid.

Inceptisols

young soil with weak horizon development, The processes of A horizon depletion (eluviation) and B horizon deposition (illuviation) are just beginning, usually because of a very cold climate, repeated flood-related deposition, or a high rate of soil erosion

Mohorovičić discontinuity or Moho

zone marking the transition between Earth's crust and the denser mantle, named after the Croatian geophysicist who first detected it in 1909, does not lie at a constant depth but generally mirrors the surface topography, being deepest under mountain ranges where the crust is thick and rising to within 8 kilometers (5 mi) of the thin ocean floor

B horizon

zone of accumulation, where much of the materials removed from the A and E horizons are deposited, generally has little humus