Geography

Geomorphology

the study of the characteristics, orgin and development of landforms

Igneous Rocks

"ingi" latin for fire. Solidified hot molten lava (magma) that originated below the Earth's crust. Subduction of the sedimentary & metamorphic rock re-emerges as magma at great distances from the point of subduction and through solidification reforms into new igneous rocks. "The mother of all rocks" All rocks begin as igneous. 2 types: Extrusive: formed when lava is extruded to the surface through volcanic activity. It quickly cools to form fine crystalline rocks such as Basalt, rhyolite, or andesite. Intrusive: Formed when magma cools and solidifies in subsurface chambers or is intruded between overlying layers of rock, creating course crystalline rocks such as gabbo (iron & Silica) or Granite (rich in Aluminum and silica) depending on the chemical compostion of the magma.

Landform

an individual topographic feature of whatever size.

Erosion features of Alpine Glaciation

aretes, horns, cirques( broad ampitheatre hollowed out at the head of a glacial valley), glacial troughs, and hanging valleys. Depositional features are terminal, lateral, and recessional medial moraines and tills.

Rock Cycles

The 3 rock types appear hard/permenant, but are a part of a cycle of formation and destruction.Igneous rocks are transformed by weathering and erosion into sedimentary rocks and into metmorphic rocks from heat and pressure. Sedimentary & metamorphic rocks by melting at subductions can become igneous rocks at solidification. Sedimentary rocks can become metamorphic rocks by heat and pressure. Metamorphic rocks can become sedimentary rocks by erosion and weathering.

Chemical Weathering

Usually, but not always, accompanies mechanical weathering. It is the dec omposition of rock by the chemical alteration of its minerals. Almost all minerals are subject to alteration through atmospheric and biotic agents.Quartz is resistant to chemical change. Requires moisture. More rapid in humid climates.

Denudation

An overall effect of disintegration, the weraing away and removal of rock by external forces. It involves 3 related external forces: Weathering Mass Wasting Erosion

Weathering

Breaks down rocks into smaller components by atmospheric and biotic agents. Refers to a group of processes by which surface rock disintegrates into smaller particles or dissolve into water due to the impact of the atmosphere and hydrosphere. Weathering processes are often slow (100 to 1000's of years). The amount of time the rocks and minerals are exposed at the Earth's suface influences the degree in which they have weathered. Divided into 3 catagories: Physical (mechanical) weathering, chemical weathering, and biological weathering.

Underground water

Can influence surface topography. Especially true in humid regions underlain by soluable rock such as limestone. Water beneath surface moves slowly through limestone structure and through chemical action dissolves the rock, creating erosion features such as caverns, stalamites and stalactites, and transporting some of the material and deposit it in new forms. Most activity takes place underground, but there are feautures that develop on the surface. The collection of these surface landforms is known as Karst topography. It is characterized by sinkholes, collapsed surfaces known as dolines and disappearing streams as seen on the Yucatan Peninsula in Mexico.

Coastal Water and related processes

Coastlines are shaped by agitated water crashing and lapping against them, with the result that coastal terrain is often quite different from the terrain of the shore just a short distance away. Coastal processes affect only a tiny fraction of the total area of Earth's surface but they create a landscape that is almost entirely different than any other on the planet. Landforms in coastal areas are primarily formed by waves and these waves are primarily a result of wind. Tides and infrequent diatrophic events (earthquakes generated tsunamis) can contribute to water motion in coastal regions but they are secondary to waves in the development of coastal landform features. Most notable features created by waves are rock cliffs and headlands. Other common landform complexes include wave cut cliffs and wave cut platforms. Extensive erosion changes the shape of coast lines after major storms. Despositional features are diverse, but the most common are beaches and sandbars. Others include barrier islands and spits.The outflows of sediment from river streams into oceans provide the sand for creating beaches. Most of the sediments are carried to shore by long shore currents and deposited on the shore to create beaches by wave action. Shorelines of emergence (rising because internal tectonic forces) and changes in sea level create unique landforms in some coastal regions such as the marine terraces.

Extrusive Vulcanism

Commonly known as Volcanism, can produce an almost infinate variety of terrain features, the most common are: Lava flows/Shield volcanoes, cinder cones. composite volcanoes, calderas, and volcanic necks. The magma that is extruded on Earth's surface is called lava. The explosive eruption of a volcano extrudes lava and often is accompanied by other material suchas rock fragments, solidified lava blobs, ashes, and dust. Collectively, these are known as PYROCLASTIC MATERIAL. Magma contains phospherous, potassium, calcium, magnesiuym, and sulfur which are essential to plant growth. Some of the Earth's most fertile areas occur in Volcanically active areas. Volcanism may be explosive and devestating as in the case of volcano eruptions or may take more subtle forms as lava flows slowly moving over Earth's surface.

Sedimentary rocks

Formed when loose grains from other rocks are transported to new locations arelater consoldated. Sandstone is solidified from the layers of desposited sand. Limestone from compaction of the remains of marine organisms. Main characteristic is that they occur in layers known as strata. Each layer reflects the conditions that were around when they were laid down. Most are formed by the transport by water of rocks that have been disintegrated by weathering and ultimately laid down in a quiet body of water, most commonly on the bottom of oceans. Sedimentary deposits can accumualte to great thickness, many 1000's of ft. Water perculating into sediment, carries cementing agent such as silica, calcium carbonate and iron oxide precipitate into the pores of the sediments and cause them to consolidate into sedimentary rocks. Majority are limestone, sandstone, shale. Strata is made visible through weathering and erosion. Layers are often folded due to internal forces associated with plate tectonics.

Diastrophism

General term that refers to the deformation of the Earth's crust. Term covers a variety of crustal movements in 2 catagories: Folding and Faulting. The process deals with solid rock. Rocks are bent and broken in a variety of ways in response to great pressures exerted either in the mantle of crust.

Distribution of rocks at/near Earth's surface

96% of crust Igneous and metamorphic. 4% is sedimentary. Whereas crust is primarily igneous, the portion of crust closest to and at the surface is sedimentary. Sedimentary rocks normally occurring in layers no thicker than 1.5 miles yet occupy 75% of exposed surface. Igneous and metamorphic rocks 25%. Extensive distribution of sedimentary rocks is primarily related to constant wearing down (weathering and erosion) of igneous and metamorphic rocks and the deposition of eroded material to other locations. Large quantities of biomass deposited along with sediments in shallow seas during the carboniferous period evovled into fossil fuels like oil, natural gas, and coal in sedimentary rock layers.

Vulcanism

All phenomena connected to the orgin and movement of molten rock (magma) that originated below the Earth's crust. Extrusive Vulcanism: Volcanism, when magma is expelled onto Earth's surface while still molten. Intrusive Vulcanism: When magma is solidified in the crust.

Metamorphic Rocks

Form from the alteration of other types of rock mainly by the melting, contorting, and recrystallizing of other rocks (by heat and pressure). Deep in the ground tectonic forces squeeze, fold, heat and recrystallize solid rock. Under these conditions chemical reactions can alter both the composition and structure of the component elements. The metamorphic rocks that form under extreme pressure and heat are rocks such as jade and diamonds. Metamorphic rocks that form under moderate heat and pressure conditions include graphite and talc. Other examples: Marble from alteration of limestone, slate from mudstone and shale, quartzite from sandstone.

Mass wasting

Involves downslpoe movement of broken rock material due to gravity. It can take many forms, from a deadly mudflow rushing down the mountain to devestating landslides which deliver tons of debris down the mountain side in just seconds. More sublte forms are Creep, where the movement downslope is almost imperceptible. Since slopes are most common landform, mass wasting operates over virtually the entire surface of the Earth.It is a continuous chain of processes that move Earth materials from the tops of the highest mountains down to the deep ocean floor. 2 driving forces: Tectonic activity, the uplifting & mountain building that continuouslt maintain the slopes, and Gravity, which tends to pull the slopes down and even out the landscape. Mass Wasting is a natural process that continuously shapes the landscapes.

Fluvial Processes.

Involves running water and is the most important agent of erosion because it happens almost everywhere from precipitation. Encompasses overland flow (unchanneled downslope movement of surface water) and stream flow (channeled movement of water along a valley bottom). Contibutes towards shaping landforms and sculturing the land more than any other external agents combined.The basic effect of running water is to smooth irregularities, to wear down the hills by erosion and fill up valleys by deposition.. Fluvial action often creates deep canyons and steep slopes that remain for long periods of time, particularly if the region is subjected to uplkift by internal forces (Grand Canyon). Erosive wroks of rivers is conspicuous. Major erosional features associated with fluvial processes are rills, gullies, V shaped canyons, valleys, straight channels, sinuous channels, meandering channels and floodplains.In desert regions prominent erosional features include measa and scraps, and the clearly sculptured nature of mountains. The effects of differential erosion of mountains are often visible in deserts. MAJOR DEPOSITIONAL features are deltas, natural levees, some floodplain features, meandering channels, and alluvial fans in desert regions.

Erosion

Involves the extensive and generally more distantremoval of weathered rock material by external agents of running water (Fluvial processes), moving ice (Glaciation), coastal waters, wind (aeolian processes) and subsurface waters (in order of impotance). Erosional processes are often distinct scultured landforms; leads to the formation of despositional features. It removes surface material from the Earth's crust, primarily soil and rock debris, and the transports of those materials by natural agencies from the point of removal.

Intrusive Vulcanism

Involves the solidification of magma within the Earth's crust. Some of these intrusions have a direct effect on topography as crustal material is raised. Many are far enough below surface to have no effect on topography. Common features are: batholiths, stocks, laccoliths, dikes, and sills.Often some of these intrusive features such as batholiths are a fundamental part of mountain building processes as is the case in the Sierra Nevadas. The granitic blocks of rock that make up most of the Sierra NV Mountain range are exposed portions of a batholith.This batholith is visible today since the original overlying crustal material has been eroded away.

Internal processes

Less extensive internal processes, Diastrophism & vulcanism, occur within tectonic plates and result in landform features that are less extensive from a geographic view in comparison to the plates themselves. The forces that create lanform features that characterize the topography of many regions. For example, the Sierra Nevada Mountain Range, the Rocky Mountains, and the Cascade Mountains of OR & WA. Vulcanism ad diastophism are intimately related to the larger tectonic movements of the plates.

Glaciation

Moving ice. Have modified topography on many parts of the continents and the results are imprinted on terrain. Most of the glacial features that we observe today were formed during the Pleistocene epoch (ice age), a period from approx. 2 million yrs ago to about 10,000 years ago. There were 5 glacial periods with 2 types of glaciers. Continental (ice sheets) & Alpine (highland). Continental glaciations modified flat landscapes greatly with the result that post glacial slope, drainage, and superficial material are most often totally different than they were before the glacier past. Alpine glaciation in mountainous regions results in metamorphisis of the landscape but to a lesser degree. However, topogrphy is deepened, steepened and sharpened creating spectacular landforms. Glacial processes are still at work today, but are less significant than it was a few thousand years ago.

Biological Weathering

Plants frequntly and animals occasionally contribute to weathering. They invlove living organisms. Most noatable is the penetration of growing plat roots into cracks and crevices. Burrowing by animals mixes soil effectively and sometimes is a factor in rock disintegration. Total effects of biotic actions is likely significant but difficult to evaluate because may be obscured by subsequent chemical and physical weathering.

Crustal rearrangement

Portions of the mantle circulate in convective currents that break the overlying crust into a mosaic of huge blocks known as Tectonic plates.The movement of the tectonic plates is crustal rearrangement.. 200 mil years ago, it is believed that there was one large continent, named Pangaea by Alfred Wegener when he published his theory of Continental Drift in 1913. This theory was criticized and in part discarded . In the late 60's, plate tectonics became established based on new scientific eveidence.

Faulting

Prominent feature of crustal stresses, the breaking apart of rock material.When rock is broken and is accompanying displacement (the actual movement of the crust on one or both sides of the break) the action is called faulting. Movement can be vertical, horizontal, or a combiunation of both. Normally takes place along Fault Zones, zones of weakness in the crust. Insection of fault zone and Earth's surface is a Fault line. Movements along a fault zone are sometimes very slow, but may occur as a sudden slippage. A single slippage may result in a displacement of ony a few inches but in some cases movement may be as much as 30 ft. Major faults penetrate many km into Earth's surface. Deeper fault zones serve as conduits to allow both water and heat from inside the Earth to approach the surface. Springs are frequently found along fault lines, sometimes gushing hot water. Volcanic activity is also associated with some fault zones as magma forces it way upward in the zone of weakness. Earthquake magnitude describes the relative amount of energy released. They are based on a logarithmic scale w/ an energy increase from one magnitude to the next of about 32 times. Ex: Magnitude 4 earthquake releases 32x's more energy than a magnitude 3. Types of faults: Strike slip, thrust, reverse, normal.

Physical Weathering

Same as Mechanical. Physical disintegration of rock material without any changes to its chemical composition.Big rocks are mechanically weathered into small rocks by various stresses that cause the rock to fracture into smaller fragments. Most occurs at or near the Earth's surface, but in certain conditions may occur at considerable depth. Exfoliation: curved layers peel off bedrock.

Relief

The difference in elevation between the highest and lowest points in an area. The vertical variation from a mountain top to a valley bottom.

Rocks

The solid inorganic portion of the Earth known as the lithosphere. They are made up of solid cohesive aggregates of inorganic solid material and are chartacterized by a mix of minerals and grain sizes. 3 types: Igneous, sedimentary, and metamorphic. A mineral is a naturally occurring inorganic solid with a definate chemical composition and specific internal crystal structure. Ice is a mineral for it has a crystal structure. Magma is not, but when it solidifies into a rock and crystals form it is then considered a mineral. Common minerals: silicates, oxides, sulfides, sulfates, carbonates, and halides.

Convergent Boundaries

Zones where the plates converge toward each other. 3 variations exist: Oceanic-Continental Oceanic-Oceanic Continental-Continental

Plate boundaries

There are 13 major plates and several smaller plates that have been identified. The crustal movements of these plates vary and are defined by the boundaries between them. The 3 boundaries between plates are convergent, divergent, and transform boundaries.

Folding

When crustal rocks are subjected to certain forces particularly lateral compression, they are often deformed by being bent in the process called folding. Can occur in any type of rock but it is most recognizable in sedimentary strata. Mostly takes place in constrictly subterranean environment; when exposed at the surface, erosion modifies them in a variety of ways. Major types of folds are anticlines (symetrical upfold), synclines (down fold), monoclines (one-sided fold- a slope connecting 2 horizontal or gently inclined strata), overturn (upfold that has been pushed so extensively from one side that it becomes oversteepened enough to have a reverse orientation on the other side) and overthrust (when pressure is enough to break the oversteepened limb and cause a sheering movement, which causes the older rock to ride above the younger rock).

Aeolian Processes

Wind action. Pronounced where ever fine-grained unconsolidated sedimentary material is exposed to atmosphere, without the protection of vegetation or moisture. Confined mainly to desert regions and along sandy beaches.The erosive force of the wind works trough deflation (the shifting of loose particles either being blown through the air or along the ground) and abrasion (when wind drives air particles into rock and soil forms as a result of this sandblasting action).Deflation causes shallow depressions(blowouts) and the pitting, etching, faceting, & polishing of rock surfaces. Most notable depostional feature is the formation of sand plains and sand dunes. Dunes patterns (almost infinate) 3 best known: Barchans, transverse dunes and seifs.

Oceanic-Continental Convergence Boundaries

Zone where oceanic lithosphere dives below continental lithosphere. This is known as the process of SUBDUCTION (some believe that this subduction action is a driving force in plate movements.Landform features that occur: Mountain ranges formed on land (ex: Andes) and parallel deep trenches at the sea floor. Earthquakes vary from shallow to increasingly deep siesmic events as the plate is subducted into the mantle.

Continental-Continental Convergence Boundaries

Zones where 2 continental plates collide. No subduction takes place in these zones because the continental material is too buoyant to subduct and extensive mountain ranges are built as the plates collide. (Himalayas-result of India crashing into asia- and the Alps). Under these conditions of continental collision, volcanoes are rare but shallow force earthquakes and regioal metamorphism are common.

Oceanic-Oceanic Convergence Boundaries

Zones where 2 oceanic plates converge.Normally, deep oceanic trenches are formed and a series of volcanoes form on the ocean floor. These types of volcanoes develop into a series of volcanic island arcs such as Aleutian and Mariana Islands. (Mariana trench extends 35,000 ft below sea level.) Seismic events are common in these areas often accompanied by l;arge displacements of crustal material which in turn may generate Tsunamis.

Divergence boundaries

Zones where 2 plates are moving away from each other because of magma upwelling from the mantle. Magma from the Asthensophere wells up in an opening betweeen plates and this flow of molten material produces a continuous line of active volcanoes that spill out Basalt onto the ocean floor creating new crustal material. Typically a ridge is formed in this area. Most divergent boundaries occur on the sea floor, but some appear on Continents such as the rift valley in E Africa. These are zones of shallow earthquakes, volcanic activity, and hyrothrmal metamorphism. Said to be constructive because material is being added to Earth's crust. The Atlantic ocean was created by the divergence of 2 plates.Ocean basins are formed where crustal material is forced apart by injection of magma.The Atlantic ocean, for example, is growing slowly as Europe and Africa pull apart from N & S America. This is known as seafloor spreading. Magma from below the crust is forced up through cracks and solidifies forming new oceanic crust that piles up underwater in midocean ridges, creating large and extensive mountain ranges in the ocean.

Transform boundaries

Zones where 2 plates slip past one another laterally. Unlike convergent and divergent zones, tyhis lateral movement neither creates nor destroys crustal material.They create extensive fractures known as transform faults and these zones are charaterized by a great deal of siesmic activity, such as those areas along the transform boundary in CA, the San Andres Fault, where the pacific plate is sliding past the North American plate. In 30 mil years, LA will pass SF as it drifts towards Alaska.

Erosional features of Continental Glaciation

glacial valleys that become lakes, roche moutonnee, ice-scoured rocky knobs and scooped out depressions that become lakes of varying sizes. Major depositional features are: till plains, moraines, and drumlins.

Topography

surface configuration of the Earth. The form of the land or landforms.