Chapter 16 Weather, Erosion, and Mass Wasting: Interactions Between the Climate and Plate Tectonic Systems

angle of repose

The slope angle of the sand pile is its ___ ____ ____, the maximum angle at which a slope of loose material will lie without cascading down

Weathering

_______ is the general process by which rocks are broken down at Earth's surface

slump

In a , a mass of unconsolidated material slides slowly downslope as a unit, leaving a scar at its source

rate of dissolution

A mineral's ___ ___ ___ is measured by the amount of that mineral that dissolves in an unsaturated solution in a given time. The faster the mineral dissolves, the less stable it is.

acid

An ____is a substance that releases hydrogen ions (H+) to a solution. A strong ____ produces abundant hydrogen ions; a weak one, relatively few. The strong tendency of hydrogen ions to combine chemically with other substances makes ____'s excellent solvents.

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Factors that influence weathering and erosion: Duration of weathering mineral composition temp amount of rainfall rainfall acidity topography

1. Parent material: the solubility of minerals, the sizes of grains, and the patterns of fragmentation, such as joints and cleavage, in the bedrock 2. Climate: temperatures, precipitation levels, and their seasonal patterns of variation 3. Topography: slope steepness and the direction the slope faces: gentler slopes that face toward the Sun promote better soil development 4. Organisms: the diversity and abundance of organisms living in the soil 5. Time: the amount of time that a soil has to form

Five factors important in soil formation:

soil

Geologists use the term____ to describe layers of material, initially created by fragmentation of rock during weathering, that experience additions of new materials, losses of original materials, and modification through physical mixing and chemical reactions.

Intro

In this chapter, we will describe three geologic processes that break down rocks and transport the products over short distances: weathering, erosion, and mass wasting. These three processes result from interactions between the climate and plate tectonic systems. Weathering is the first step in flattening the mountains that have been uplifted by plate tectonic processes. Even as mountains are being uplifted, chemical decay and physical fragmentation join with rainfall, wind, ice, and snow to wear them away.

*5 of 6 (Summary)* What are mass movements, and what kinds of materials do they move?

Mass movements are slides, flows, or falls of large masses of material downslope in response to the force of gravity. The movements may be imperceptibly slow or too fast for a human to outrun. The masses may consist of consolidated material, including rock and compacted or cemented sediments; or unconsolidated material. Mass movements of rock include rockfalls, rockslides, and rock avalanches. Mass movements of unconsolidated material include creep, slumps, debris slides, debris avalanches, earthflows, mudflows, and debris flows.

1. Nature of slope materials 2. Amount of water in materials 3. Steepness of slope

Mass wasting is influenced by three primary factors: the

carbonic

On Earth's surface, the most common acid—and the one most responsible for increasing weathering rates—is _____acid (H2CO3). This weak acid forms when carbon dioxide (CO2) gas from the atmosphere dissolves in rainwater: carbon dioxide + water -----> carbonic acid CO2 - H2O - H2CO3

frost wedging

One of the most efficient mechanisms for widening cracks in rock is _____ _____: breakage resulting from the expansion of freezing water. As water freezes, it expands, exerting an outward force strong enough to wedge open a crack and split a rock

humus

Organic matter, called _____, is an important component of most of Earth's soils; it consists of the remains and waste products of the many organisms that live in soil.

hematite

Oxygen atoms in air and water oxidize ferrous iron to form ferric iron. Thus, all the iron oxides formed at Earth's surface, the most abundant of which is ______ (Fe2O3), are ferric. Oxidation, like hydrolysis, is one of the important reactions of chemical weathering.

*3 of 6 (Summary)* What are the processes of physical weathering?

Physical weathering breaks rocks into fragments along preexisting zones of weakness or along joints and other fractures in massive rock. Physical weathering is promoted by frost wedging and by burrowing and tunneling by animals and tree roots, all of which expand cracks. Microorganisms contribute to both physical and chemical weathering. Patterns of breakage such as exfoliation probably result from interactions between chemical weathering and temperature changes.

paleosols

Recently, there has been much interest in ancient soils that have been preserved as rock in the geologic record. These ______, as they are called, are being studied as guides to ancient climates and even to the amounts of carbon dioxide and oxygen in the atmosphere in former times

*1 of 6 (Summary)* What is weathering and how is it controlled?

Rocks are broken down at Earth's surface by chemical weathering—the chemical alteration or dissolution of minerals—and by physical weathering—the fragmentation of rocks by mechanical processes. Erosion dislodges the products of weathering, which are the raw materials of sediments, and moves them away from their source. The properties of the parent rock affect weathering because different minerals weather at different rates and have differing susceptibilities to fracturing. Climate strongly affects weathering: warmth and heavy rainfall speed weathering; cold and dryness slow it down. The presence of soil accelerates weathering by providing moisture and acids secreted by organisms. The longer a rock weathers, the more completely it breaks down.

stress, biological, chemical

Rocks can break for a variety of reasons, including _____along natural zones of weakness and _____and _____ activity.

rind

Rocks that have been exposed to Earth's surface for many thousands of years form a ____ an external layer of weathered material ranging from several millimeters to several centimeters thick that surrounds fresh, unaltered rock.

*4 of 6 (Summary)* What factors are important in soil development?

Soil is a mixture of rock particles, clay minerals, and other products of weathering, as well as humus. It develops through inputs of new materials, losses of original materials, and modification through physical mixing and chemical reactions. The five key factors that affect soil development are parent material, climate, topography, organisms, and time.

solubility, Saturation

The _____ of a mineral is measured by the amount of that mineral dissolved in water when the solution is saturated. _____ is the point at which the water cannot hold any more of the dissolved substance.

soil profile

The composition and appearance of a soil is known as a ____ _____.

(1) properties of the parent rock, (2)the climate, (3)the presence or absence of soil, (4)and the length of time the rocks are exposed to the atmosphere

The four key factors that control rates of weathering are the: (1) (2) (3) (4)

oxidation

The iron in minerals may be present in one of three forms: metallic iron, ferrous iron, or ferric iron. In the metallic iron found in meteorites (and in manufactured items), the iron atoms are uncharged: they have neither gained nor lost electrons by reacting with another element. In the ferrous iron (Fe2+) found in silicate minerals, the iron atoms have lost two of the electrons they have in the metallic form and have thus become ions. In the ferric iron (Fe3+) found in iron oxide minerals, the iron atoms have lost three electrons. The electrons lost by the iron are gained by oxygen atoms in a process called _____.

creep

The slowest type of unconsolidated mass movement is _____: the gradual downhill movement of soil or other debris

*6 of 6 (Summary)* What factors are responsible for mass movements, and how are such movements triggered

The three factors that have the greatest bearing on the predisposition of material to move down a slope are the nature of the slope material, the water content of the material, and the steepness of the slope. Slopes made up of unconsolidated material become unstable when they are steeper than the angle of repose, the maximum slope angle that the material will assume without cascading downslope. Slopes made up of consolidated material may also become unstable when they are steepened or denuded of vegetation. Water absorbed by slope material contributes to instability by lowering internal friction and by lubricating planes of weakness in the material. Mass movements may be triggered by earthquakes, heavy rainfall, or gradual steepening of a slope due to erosion.

*2 of 6 (Summary)* What are the processes of chemical weathering?

The weathering of feldspar, the most abundant silicate mineral, serves as an example of the processes that weather most silicate minerals. In the presence of water, feldspar undergoes hydrolysis to form kaolinite. Carbon dioxide (CO2) dissolved in water promotes chemical weathering by reacting with the water to form carbonic acid (H2CO3). The slightly acidic water dissolves away potassium ions and silica, leaving kaolinite. Iron (Fe), which is found in ferrous form in many silicate minerals, weathers by oxidation, producing ferric iron oxides. These processes operate at varying rates, depending on the chemical stability of the minerals involved under various weathering conditions.

kaolinite

The white to cream-colored clay produced by the weathering of feldspar is called _____, named for Gaoling, a hill in southwestern China where it was first obtained. Chinese artisans had used pure _____ as the raw material of pottery and porcelain for centuries before Europeans borrowed the idea in the eighteenth century.

1. It leaches, or dissolves away, cations and silica. 2. It hydrates, or adds water to, the minerals. 3. It makes solutions less acidic.

Three main effects of chemical weathering on silicates:

liquefaction.

When the ground becomes saturated with water, the planes of weakness within the solid material are lubricated, the friction between particles is lowered, and the particles or larger aggregates can move past one another more easily, so that the material may start to flow like a fluid. This process is called _____.

Chemical stability

Why do chemical weathering rates vary so widely among different minerals? Minerals weather at different rates because there are differences in their _____ _____ in the presence of water at given temperatures. _____ _____ is a measure of a substance's tendency to retain its chemical identity rather than reacting spontaneously to become a different chemical substance.

Chemical weathering

_______occurs when the minerals in a rock are chemically altered or dissolved when minerals react with air and water.

mass movements

____ ______ occur when the force of gravity exceeds the strength of the slope materials. The materials then move down the slope, sometimes very slowly, sometimes as a large, sudden, catastrophic movement. _____ ______can displace small, almost imperceptible amounts of soil down a gentle hillside, or they can be huge landslides that dump tons of earth and rock on valley floors below steep mountain slopes.

Soils

____ form at the interface between the climate and plate tectonic systems. They are crucial to life on Earth's continents, and they are one of human society's most valuable natural resources. _____are the primary reservoir of nutrients for agriculture and the ecological systems that produce renewable natural resources. They filter our water and recycle our wastes, and they provide the necessary substratum for our buildings and infrastructure. In addition, they help regulate the global climate by storing and releasing carbon dioxide. _____contain twice as much carbon as the atmosphere and three times more than all of the world's vegetation.

talus

____ is the pile of rocks that accumulates at the base of a cliff, chute, or slope.

Mass Wasting

_____ _____ includes all the processes by which weathered and unweathered Earth materials move downslope in larger amounts and in large single events, usually by means of gravity.

Physical weathering

_____ _____ takes place when solid rock is fragmented by mechanical processes that do not change its chemical composition

Kaolinite

_____ is a hydrous aluminum silicate. In the reaction that produces it, the solid feldspar undergoes hydrolysis (a decomposition reaction involving water; from hydro, "water," and lysis, "to loosen"). The feldspar is broken down and also loses several chemical components, while _____ gains water.

Erosion

_____ is the process by which particles produced by weathering are dislodged and removed from their source, usually by means of currents of water or air.

Erosion, Mass Wasting, Erosion

______ and ____ wasting are the processes that loosen weathered soil and rock and transport it downhill or downwind. _____ generally refers to processes that move Earth materials on a grain-by-grain basis. _____ wasting refers to processes that cause large masses of material to collapse and move downslope. Both processes carry weathered material away from its source, exposing fresh, unaltered rock surfaces to weathering.

Weathering and the Plate Tectonic System

______ and the ___ ___ ____ are linked.. Has to do with carbon Dioxide(C02). C02 like water is involved in chemical reactions and weathering. Thus variation in atmosphere concentration of CO2 leads to variations in the rate of weather. Increases in atmospheric CO2, a greenhouse gas, make Earth's climate warmer and thus promote weathering. The weathering of calcium-rich rock, in turn, removes CO2 from the atmosphere, making global climates cooler. Cycle repeats.

Translocations

______ are lateral and vertical movements of materials within the developing soil.

Feldspar

______ is the most abundant mineral in Earth's Crust. It is one of many silicates that are altered by chemical reaction to form clay minerals and it's behavior during weathering helps us understand the weathering process in general, for two reasons: 1. _____ is a key mineral in a great many igneous, sedimentary, and metamorphic rocks and is one of the most abundant minerals in Earth's crust. 2. The chemical processes that characterize _____weathering also characterize weathering in many other kinds of minerals.

Exfoliation

_____is a physical weathering process in which large flat or curved sheets of rock are detached from an outcrop. These sheets may look like the layers peeled from a large onion

Cohesion

_____is an attractive force between particles of a solid material that are close together.

surface tension

the attractive force between molecules at a surface