Chapter 10

What does the USDA think of using conservation tillage on 80% US cropland?

it would reduce soil erosion by at least half.

Core

*Very hot and has a solid inner part, surrounded by a liquid core of molten material *Surrounded by the mantel (a thick, solid zone)

Crop rotation

Farmers plant areas or strips with nutrient-depleting crops (corn, tobacco, cotton) one year. In the next year they plant the same area with legumes (with root nodules that add nitrogen to the soil). In addition to helping restore soil nutrients, this method (1) reduces erosion by keeping the soil covered with vegetation and (2) helps reduce crop losses to insects by presenting them with a changing target.

Conventional-tillage farming

Farmers plow the land and then break up and smooth the soil to make a planting surface. In areas such as the midwestern US, harsh winters prevent plowing just before the spring growing season. Thus crop fields often are plowed in the fall. This leaves the soil bare during the winter and early spring and makes it vulnerable to erosion.

Give examples of activities that leave soil vulnerable to erosion. What can such activities do?

Farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation, and other activities that destroy plant cover.They can speed up erosion and destroy in a few decades what nature took hundreds to thousands of years to produce.

What are the two main agents of erosion?

Flowing water and wind.

What are the three major rock types?

Igneous rock, sedimentary rock, and metamorphic rock.

Where does the most severe salinization occur?

In Asia, especially in China, India, and Pakistan.

Where are erosion rates even higher?

In heavily farmed regions.

Where are varying amounts of air and water often kept? What is most of the air?

In the spaces, or pores, between the solid organic and inorganic particles in the upper and lower soil layers. Most of the air is nitrogen and oxygen gas.

Mechanical weathering

In which a large rock mass is broken into smaller fragments of the original material.

Convection cells

In which large volumes of heated rock move, following a pattern resembling convection in the atmosphere or a pot of boiling water.

Mantle plumes

In which mantle rock flows slowly upward in a column (like smoke from a chimney on a cold morning). When the moving rock reaches the top of the plume, it moves out in a radial pattern, as if it were flowing up an umbrella through the handle and then spreading out in all directions from the tip of the umbrella to the rim.

Chemical weathering

In which one or more chemical reactions decompose a mass of rock. Most chemical weathering involves a reaction of rock material with oxygen, carbon dioxide, and a moisture in the atmosphere and the ground.

Frost wedging

In which water (1) collects in pores and cracks of rock, (2) expands upon freezing, and (3) splits off pieces of the rock.

Where does the information that we have about the earth's interior mostly come from? (5)

Indirect evidence. 1.) Density measurements 2.) Seismic (earthquake) wave studies 3.) Measurements of heat flow from interior 4.) Lava analyses 5.) Research on meteorite composition

Some of the country's most productive agricultural lands (such as those in Iowa) have...

Lost about 1/2 of their topsoil.

What are the two types of weathering processes?

Mechanical weathering and chemical weathering

What is the earth's crust composed of? What does it do?

Minerals and rocks. It is the source of almost all nonrenewable resources we use: fossil fuels, metallic minerals, and nonmetallic minerals. It is also the source of soil and of the elements that make up our bodies and those of other living organisms.

What are some of the benefits of volcanic activity?

Outstanding scenery and the highly fertile soils that are produced by the weathering of lava.

How do geologists identify these three major concentric zones?

The core, the mantle, and the crust.

what is the next layer called?

The topsoil layer or A horizon.

Soil structure

The ways in which soil particles are organized and clumped together.

Continental crust

Underlies the continents (including the continental shelves extending into the oceans).

Oceanic crust

Underlies the ocean basins and covers 71% of the earth;s surface.

Describe the particles in clay soils.

Very small and easily compacted. When these soils get wet, they form large, dense clumps. They are more porous and have a greater water-holding capacity than sandy soils, but the pores are so small that these soils have a low permeability. Because little water can infiltrate to lower layers, the upper layer can easily become waterlogged for growing most crops.

What happens to this soil without adequate drainage?

Water accumulates underground and gradually raises the water table. Saline water then envelops that deep roots of plants, lowering their productivity and killing them after prolonged exposure. *At least 1/10th of all irrigated land worldwide suffers from water-logging, and the problem is getting worse.

What are fine particles needed for?

Water retention.

What are we able to do by reconstructing the course of continental drift over millions of years?

We can trace how life-forms migrated from one area to another when continents that are now far apart were still joined together.

When is some erosion caused?

When the wind blows particles of soil from one area to another.

Convergent plate boundaries

Where the plates are pushed together by internal forces.

Divergent plate boundaries

Where the plates move apart in opposite directions.

Transform faults

Which occur where plates slide past one another along a fracture (fault) in the lithosphere.

The proportion is much higher in some heavily irrigated western states including...

(1) 66% of the irrigated land in the lower Colorado Basin and (2) 35% of such land in CA

Scientists are also studying phenomena that precede an eruption such as... (5)

(1) Tilting or swelling of the cone, (2) changes in magnetic and thermal properties of the volcano, (3) changes in gas composition, and (4) increased seismic activity.

Windbreaks or shelterbelts

(of trees) established to (1) reduce wind erosion, (2) help retain soil moisture, (3) supply some wood for fuel, ad (4) provide habitats for birds, pest-eating and pollinating insects, and other animals.

Conservation-tillage farming

*(Either minimum-tillage or no-till farming) The idea is to disturb the soil as little as possible while planting crops.

Mantel

*A thick, solid zone that is surrounding the core *Mostly solid rock, but under its rigid outermost part is a zone of very hot, partly melted rock that flows like soft plastic. This plastic region of the mantle is called the asthenosphere.

Inorganic commercial fertilizers downsides

*Doesn't add humus to soil, reduces soil content of organic matter and its ability to hold water, lowering the oxygen content of soil and keeping fertilizer from being taken up as efficiently, typically supplying only 2 or 3 of the 20 or so nutrients needed by plants, requiring large amounts of energy for their production, transport, and application, and releasing nitrous oxide, (N20) - a GHG that can enhance global warming, from the soil. *The widespread use of commercial inorganic fertilizers, especially on sloped land near streams and lakes, also causes water pollution as nitrate (N03) and phosphate (P04) fertilizer nutrients are washed into nearby bodies of water.

Inorganic commercial fertilizers benefits

*Easily transported, stored, and applied. *The additional food these fertilizers help produce feeds one of every three people in the world. Without them the world food output would drop an estimated 40%.

The Great Plains

*Has lost 1/3 or more of its topsoil in the 150 years since it was first plowed.

Streams

*Operate everywhere on the earth (except for the polar regions) *They produce valleys and canyons, and may form deltas where streams flow into lakes and oceans.

What are the most effective ways to slow desertification?

*Reduce (1) over-grazing, (2) deforestation, and 3) destructive forms of planting, irrigation and mining. *Plant trees and grasses that will (1) anchor the soil, (2) hold water, and (3) help reduce the threat of global warming by increasing uptake of carbon dioxide from the atmosphere.

Animal manure

*The dung and urine of cattle, horse, poultry, and other farm animals *Improves soil structure, adds organic nitrogen, and stimulates the beneficial soil bacteria and fungi. *Use in the US decreased because of replacement of most mixed animal-raising and crop-farming operations with separate operations for growing crops and raising animals, the high costs of transporting animal manure from fedlots near urban areas to distant rural crop-growing areas, and the use of tractors and other motorized farm machinery to replace horses and other draft animals that added manure to the soil. *** Researchers at the USDA are evaluating the use of phosphorus-rich ash produced from buring poultry wastes to produce electricity as an organic fertilizer. ***

Crust

*The outermost and thinnest zone of the earth. *Consists of the continental crust and the oceanic crust

What did we learn from the 1999 UN conference on desertification? (2) What does this threaten?

1.) About 40% of the world's land and 70% of all drylands is suffering from the effects of desertification. 2.) Each year about 150,000 sq kl (58,000 sq m) becomes desertified. this threatens the liveliness of at least 135 million people in 100 countries and causes economic losses estimated at $42 billion per year.

In NW China, what do the resulting huge dust plumes of eroded soil do? (2)

1.) Bot out the sun and reduce visibility in China's NE cities. 2.) Reduce visibility and increase air pollution in Japan, the Korea Peninsula, and the NW USA.

Soils vary in their content of what? (4)

1.) Clay (very fine particles) 2.) Silt (fine particles) 3.) Sand (medium-sized particles) 4.) Gravel (coarse-very coarse particles)

What are the three types of boundaries of lithospheric plates?

1.) Divergent plate boundaries 2.) Convergent plate boundaries 3.) Transform faults

How can we reduce the loss of human life and sometimes property from volcanic eruptions? (3)

1.) Land-use planning 2.) Better prediction of volcanic eruptions 3.) Effective evacuation plans

What are the two major harmful effects of soil erosion?

1.) Loss of soil fertility and its ability to hold water. 2.) Runoff of sediment that pollutes water, kills fish and shellfish, and clogs irrigation ditches, boat channels, reservoirs, and lakes.

What are the (6) economic and ecological effects of soil erosion?

1.) Loss of soil organic matter and vital plants nutrients. 2.) Reduced ability to store water for use by crops. 3.) Increase use of costly fertilizer to maintain soil fertility. 4.) Increased water runoff on eroded mountain slopes that can flood agricultural land and dwellings in the valleys below. 5.) Increased buildup of soil sediment in navigable waterways and coastal areas that reduces ship navigation, decreases fish production, and harms many other forms of aquatic life. 6.) Increased input of sediment into reservoirs that shortens their useful life.

Some soil scientists point out that this global average... (2)

1.) Masks much higher rates of soil erosion in heavily farmed areas. 2.) Does not include the other harmful effects of soil erosion. *** When such effects are included, soil scientists and ecologists estimate that soil erosion causes a 15-30% reduction in crop productivity in some areas.

What two things did we learn from the 2000 study by the Consultative Group on International Agriculture Research?

1.) Nearly 40% of the world's land used for agriculture is seriously degraded by erosion, salt buildup, and water logging. 2.) Soil degradation has reduced food production on about 16% of the world's cropland.

what are the two types of fertilizers that farmers can use?

1.) Organic fertilizer (from plant and animal materials) 2.) Commercial inorganic fertilizer (produced from various minerals)

What does salinization do? (3)

1.) Stunts crop growth. 2.) Lowers crop yields. 3.) Eventually kills plants and ruins the land.

Analysts and FAQ contend that... (2)

1.) There is insufficient data on soil erosion to draw firm conclusions about its effect on crop productivity. 2.) Much of the eroded topsoil does not go far and is deposited further down a slope, valley, or plain. In some places, the loss in crop yields in one area could be offset by increased yields elsewhere.

What two things did the 1992 join survey by the UN Environment Programme and the World Resources Institute estimate?

1.) Topsoil is eroding faster than it forms on about 38% of the world's cropland. 2.) 17% of the world's land was degraded to some extent by soil erosion.

How is soil produced? (3)

1.) Weathering of rock 2.) Deposit of sediments by erosion 3.) Decomposition of organic matter in dead organisms

According to the USDA, how fast is soil on cultivated land in the US eroded?

16 times faster than it can form.

How much cropland is affected by salinization in the US?

23% of all cropland.

How much of the world's food is produced by 17% of the world's cropland that is irrigated?

40%

How much land has been desertified in the past 50 years?

8.1 sq kl (3.1 million sq m).

What has the National Resources Conservation Service set up in the US?

A classification system to ID types of land that are suitable or unsuitable for cultivation. Such efforts and recent farm legislation have helped reduce soil erosion in the US.

What is causing massive wind erosion of topsoil in Northwest China?

A combination of over-plowing and overgrazing.

Soil

A complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers.

Desertification

A complex process that involves multiple natural and human-related causes and that proceeds at varying rates in different climates.

Most irrigation water is...

A dilute solution of various salts, picked up as the water flows over or through soil and rocks. Small quantities of these salts are essential nutrients for plants, but they are toxic in large amounts.

Energy from the sun and from the Earth's interior, coupled with the erosive power of flowing water, have created what?

A dynamic planet. This has created continents, mountains, valleys, plains, and ocean basins in an ongoing process that continues to change the landscape.

Soil porosity

A measure of the volume of pores or spaces per volume of soil and of the average distances between those spaces.

Topsoil layer/A horizon

A porous mixture of partially decomposed organic matter, called humus, and some inorganic mineral particles. Usually darker and looser than deeper layers. A fertile soil that produces high crop yields has a thick topsoil layer with lots of humus. This helps topsoil hold water and nutrients taken up by plant roots. Thus the thin mantle of productive topsoil found over much of the earth's terrestrial surface is the foundation of civilization.

Humus

A porous mixture of partially decomposed organic matter.

What do earthquakes often have after/before they happen?

Aftershocks that gradually decrease in frequency over a period of up to seven months, and some have foreshocks from seconds to weeks before the main shock.

What are coarse particles needed for?

Air spaces.

What is the important of igneous rock?

Although they are often covered by sedimentary rocks or soil, they are the bulk of the earth's crust and are also the main source of many non-fuel mineral resources.

What does each unit on the Richter scale represent?

An amplitude that is ten times greater than the next smaller unit.

Mineral

An element or inorganic compound that occurs naturally and is solid.

What are the four types of organic fertilizers?

Animal manure, green manure, compost, and spores of mushrooms, puffballs, and truffles.

Rock

Any material that makes up a large, natural, continuous part of the earth's crust.

How do seismologists rank earthquakes?

As (1) insignificant (less than 4.0 on Richter scale), (2) minor (4.0-4.9), (3) damaging (5.0-5.9), (4) destructive (6.0-6.9), (5) major (7.0-7.9), and (6) great (over 8.0).

What is the typical speed of these plates?

As fast a fingernails grow.

Both convection cells and mantle plumes move upward as what happens?

As the heated material is displaced by a denser, cooler material sinking under the influence of gravity.

Where do trenches usually form?

At the boundary between the two converging plates.

Why is soil (especially topsoil) classified as a renewable resource?

Because natural processes regenerate it.

In desertification, why does the productive potential of arid or semiarid land fall by 10% or more? What can the process by like?

Because of a combination of (1) natural climate change that causes prolonged drought and (2) human activities that reduce or degrade topsoil. The process can be (1) moderate (with a 25-50% drop), or (3) very severe (with a drop of 50% or more, usually creating huge gullies and sand dunes).

Why are loams the beat soils for growing most crops?

Because they hold lots of water, but not too tightly for plant roots to absorb.

According to the National Resources Conservation Service, one third of the nation's topsoil has...

Been washed or blown into streams, lakes, and oceans. Mostly as a result of over-cultivation, over-grazing, and deforestation.

Where and when is igneous rock formed? Examples?

Below or on the earth's surface when molten rock material (magma) (1) wells up from the earth's upper mantle or deep crust, (2) cools, and (3) hardens into rock. Ex: Granite (formed underground), lava rock (formed above ground when molten lava cools and hardens).

Where is conservation tillage used?

Brazil, Argentina, Canada, and Paraguay.

How can we educe the loss of life and property from earthquakes? (4)

By (1) examining historical records and making geologic measurements to locate active fault zones, (2) making maps showing high-risk areas, (3) establishing building codes that regulate the placement and design of buildings in areas of high risk, and (4) trying to predict when and where earthquakes will occur.

What is one way to measure the severity of an earthquake?

By its magnitude on a modified version of the Richter scale.

Terracing

Can reduce soil erosion on steep slopes by converting the land into a series of broad, nearly level terraces that run across the land contour. This (1) retains water for crops at each level and (2) reduces soil erosion by controlling runoff. ***Although most poor farmers know the risk of not terracing, many have too little time and too few workers to build terraces; they must plant crops without terracing hillsides or starve. ***

What do plant roots need oxygen for?

Cellular respiration.

What can change local climates? What else does this effect?

Changes in the reflectivity of the land surface because of widespread desertification can change local climates in ways that increase drought and thus the area of land affected by desertification.

What happens when the stressed parts of the earth suddenly fracture or split?

Energy is released as shock waves, which move outward from the earthquake's focus.

By 2001....

Conservation tillage was used on about 45% of US cropland.

Surface litter layer/O horizon

Consists mostly of freshly fallen and partially decomposed leaves, twigs, animal waste, fungi, and other organic materials. Normally brown or black.

What adds to the heat flow from within?

Continued decay of radioactive elements in the crust, especially the continental crust, adds to the heat flow from within.

What are the two kinds of movement that occur in the mantle's atmosphere?

Convection cells & Mantle plumes.

What is one way to reduce nitrogen loss and the depletion of topsoil?

Crop rotation.

Which countries mainly rely on inorganic fertilizers?

Developed countries.

We live on a _______ planet.

Dynamic.

What is one major external process?

Erosion.

Green manure

Fresh or growing green vegetation plowed into the soil to increase the organic matter and humus available to the next crop.

What is the most important agent of mechanical weathering?

Frost wedging.

What are the effects of internal processes (generally)?

Generally, they build up the planet's surface.

Internal processes

Geologic changes originating from the earth's interior.

External processes

Geological changes based directly or indirectly on energy from the sun and on gravity (rather than on heat in the earth's interior).

Examples of elements?

Gold, silver, diamond (carbon), and sulfur.

What are sandy soils useful for?

Growing irrigated crops or those with low water needs, such as peanuts and strawberries.

Describe a porous soil.

Has many pores and can hold more water and air.

What provides the energy for these processes?

Heat from the earth's interior, but gravity also plays a role.

Compost

Humus-like material that is rich in organic matter and soil nutrients. It is produced when microorganisms (mostly fungi and aerobic bacteria) in soil break down organic matter such as leaves, food wastes, paper, and wood in the presence of oxygen. A rich natural fertilizer and soil conditioner that aerates soil, improves ability to retain water and nutrients, helps prevent erosion, and prevents nutrients from being wasted by being dumped in landfills.

Strip cropping

Involves planting alternating strips of (1) a crow crop (such as corn) and (2) another crop (such as a grass and legume mixture) that completely covers the soil. The cover crops strips (1) trap soil that erodes from the row crop, (2) catch and reduce water runoff, and (3) help prevent the spread of pests and plant diseases. Planting strips of nitrogen-fixing legumes (such as soybeans or alfalfa) restores soil fertility.

Contour farming

Involves plowing and planting crops in rows across the contour of gently sloped land. Each row acts as a small damn to help hold soil to slow water runoff.

Soil conservation

Involves reducing soil erosion and restoring soil fertility. For hundreds of years, farmers have used various methods to reduce soil erosion, mostly by keeping the soil covered with vegetation.

Gully Reclamation

Involves restoring severely eroded bare land by (1) planting fast-growing shrubs, vines, and trees to stabilize the soil, (2) building small dams at the bottoms of gullies to collect silt and gradually fill in the channels, and (3) building channels to divert water from the gully.

Where did this concept come from?

It became widely accepted by geologists in the 1960s and was developed from an earlier idea called continental drift.

What can stress in the earth's crust cause?

It can cause solid rock to deform until it suddenly fractures and shifts along the fracture, producing a fault . The faulting or a later abrupt movement or an existing fault causes an earthquake.

what does this heat flow from the earth's core cause?

It causes much of the mantle to deform and flow slowly like heated plastic. Ex: The same way that a red-hot iron horseshoe behaves plastically (?)

What does the rock cycle do?

It concentrates the planet's nonrenewable mineral resources on which we depend.

What happens as the water seeps down?

It dissolves various soil components in upper layers and carries them to lower layers in a process called leaching.

What happens to the irrigation water that is not absorbed into the soil?

It evaporates, leaving behind a thin crust of dissolved salts (such as sodium chloride) in the topsoil. This accumulation of salts is called salinization.

What did we learn about salinization from a 1995 study?

It had reduced yields on 20% of the world's irrigated cropland, and another 30% has been moderately salinized.

What happened as the primitive earth cooled over eons?

It interior separated into three major concentric zones.

Where and when is sedimentary rock formed? Examples?

It is formed from sediment when preexisting rocks are (1) weathered and eroded into smaller pieces, (2) transported from their sources, and (3) deposited in a body of surface water. Ex: Sandstone and shale (formed from pressure created by deposited layers of sediment), dolomite and limestone (formed from the compacted shells, skeletons, and other remains of dead organisms), and lignite and bituminous coal (derived from plant remains).

Where is the C horizon?

It lies on a base of unweathered parent rock called bedrock.

What does some of the precipitation that reaches the soil do?

It percolates through the soil layers and occupies many of the soil's open spaces or pores.

What is the topsoil production rate in tropical and temperate areas?

It takes 200-1,000 years (depending on climate and soil type) for 2.54 centimeters (1 inch) of new topsoil to form. It is renewed at an average rate of about 1 metric ton of topsoil per hectare of land per year.

What happens if topsoil erodes faster than it is formed on a new piece of land?

Its soil eventually becomes a nonrenewable resource.

Engineers...

Know how to make homes, large buildings, bridges, and freeways more earthquake resistant. But this can be expensive, especially if existing structures must be reinforced.

What is most of a soil's inorganic matter?

Mostly broken-down rock consisting of varying mixtures of sand, silt, clay, and gravel.

What does plate motion produce?

Mountains (including volcanoes), the oceanic ridge system, trenches, and other features of the earth's surface.

What do these flows of energy and heated material in the mantle convection cells cause?

Movement of rigid plates, called tectonic plates.

Some erosion is ______, and some is caused by _________ __________.

Natural, human activities.

What happened between 1985 and 1999?

Nearly 561,000 people died prematurely from natural catastrophes such as floods, earthquakes, volcanic eruptions, and wind storms. About 30% (169,000) of these deaths resulted from earthquakes and volcanic eruptions.

What do these commercial inorganic fertilizers contain?

Nitrogen (as ammonium ions, nitrate ions, or urea), phosphorus (as phosphate ions), and potassium (as potassium ions). Other plant nutrients in low or trace amounts.

Crust, mantle, and core - static?

No! They are constantly changing by geologic processes taking place within the earth and on the earth's surface, most over thousands to millions of years.

Gully erosion

Occurs when rivulets of fast-flowing water join together and with each succeeding rain cut the channels wider and deeper until they become ditches or gullies. Gully erosion usually happens on steep slopes where all or most vegetation has been removed.

Rill erosion

Occurs when surface water forms fast-flowing rivulets that cut small channels in the soil.

Sheet erosion

Occurs when surface water moves down a slope or across a field in a wide flow and peels off fairly uniform sheets or layers of soil. Because the topsoil disappears evenly, sheet erosion may not be noticeable until much damage has been done.

What happens at most convergent plate boundaries?

Oceanic lithosphere is carried downward (sub-ducted) under the island arc or the continent at a subduction zone.

Where are most of the world's crops grown?

On soils exposed when grasslands and deciduous forests are cleared.

What kind of human activities accelerate erosion?

Particularly those that destroy vegetation.

Where are natural hazards (such as volcanoes and earthquakes) likely to be found?

Plate boundaries.

What are poor farmers in developing countries doing to survive?

Plowing up marginal (easily erodible) lands.

What happened as the continents separated?

Populations become geographically and reproductively isolated and speciation occurred.

When and where is metamorphic rock formed? Examples?

Produced when a preexisting rock is subjected to (1) high temperatures (which may cause it to melt partially), (2) high pressures, (3) chemically active fluids, or (4) a combination of these agents. Ex: Anthracite (a form of coal), slate, and marble.

What happens in dry regions?

Rain does not leach away calcium and other alkaline compounds, so soils in such areas may be too alkaline (pH above 7.5) for some crops. Adding sulfur, which is gradually converted into sulfuric acid by soil bacteria, reduces soil alkalinity.

Spores of mushrooms, puffballs, and truffles

Rapidly growing and spreading mycorrhizae fungi in the spores attach to plant roots and help them (1) take in moisture and nutrients from the soil and (2) make plants more disease resistant. *** Unlike typical fertilizers that farmers must apply every few weeks, one application of mushroom fungi lasts all year and costs just pennies per plant.

Soil: Nonrenewable or renewable?

Renewable, but it is produced very slowly.

What happens as the inner core cools?

Residual heat from the earth's formation is still being given off as the inner core cools and as the outer core cools and solidifies.

What are the secondary effects of earthquakes?

Rock slides, urban fires, and flooding caused by subsidence (sinking) of land. Coastal areas can also be severely damaged by large earthquake-generated water waves (tsunamis) that travel as fast as 590 mph.

Examples of inorganic compounds?

Salt, mica, and quartz.

Alley cropping or agroforestry

Several crops are planted together in strips or alleys between trees or shrubs that can provide fruit or fuelwood. The trees or shrubs (1) provide shade (which reduces water loss by evaporation), (2) help retain and slowly release soil moisture, and (3) can provide fruit, fuelwood, and trimmings that can be used as mulch (green manure) for the crops and as fodder for livestock.

What are the primary effects of earthquakes?

Shaking and sometimes a permanent vertical or horizontal displacement of the ground.

What are the three types of water erosion?

Sheet erosion, rill erosion, and gully erosion.

What does the USDA estimate about soil erosion in the US because of soil conservation efforts?

Soil erosion in the US decreased by about 40% between 1985 and 1997. Using this data, researches estimate that soil erosion cost in the US about $30 billion in 1997, an average loss of $3.4 million per hour.

Moving water causes _____ _____.

Soil erosion.

Where is soil moisture in this equation?

Soil moisture carrying these dissolved nutrients is drawn up by the roots of plants and transported through stems and into leaves.

What does soil texture help determine?

Soil porosity.

As long as vegetation anchors these layers...

Soil stores water and releases it in a nourishing trickle instead of a devastating flood.

What is soil porosity also influenced by?

Soil structure.

Loams

Soils with roughly equal mixtures of clay, sand, silt, and humus.

What do some of these processes lead to?

Some lead to geologic hazards such as earthquakes and volcanic eruptions, and others produce the renewable soil and nonrenewable mineral and energy resources that support life and economies.

No-till farming

Special planting machines inject seeds, fertilizers, and weed killers (herbicides) into slits made in the unplowed soil.

Minimum-tillage farming

Special tillers break up and loosen the the surface soil without turning over the topsoil, previous crop residues, and any cover vegetation.

What are the most important agents of erosion?

Streams.

What causes earthquakes?

Stresses in the plate undergoing subduction at convergent plate boundaries.

Describe the top two layers of most well-developed soils.

Teemed with bacteria, fungi, earthworms, and small insects that interact in complex food webs.

Weathing

That is caused by mechanical or chemical processes usually produces loosened material that can be eroded.

What is the annual loss in crop productivity? What is the annual increase?

That the annual loss in crop productivity is only about 0.3% per year. The annual increase is 1-2%.

What do critics such as Pierre Crosson say? What do other soil scientists point out?

That these estimates of soil erosion and damages from such erosion are exaggerated and based on inexact models instead of field measurements of soil loss and sedimentation rates in nearby bodies of water. Other soil scientists point out that the current estimates by models and a few on-site measurements do not include all the ecological effects of soil erosion.

What do measurements of heat flow within the earth suggest?

That two kinds of movement occur in the mantle's atmosphere.

Where are most of a soil's inorganic matter contained?

The B horizon (subsoil) and C horizon (parent material).

Infiltration

This downward movement of water through soil (see previous flashcard).

What influences the uptake of soil nutrients by plants?

The acidity/alkalinity of a soil (measured by its pH).

What happens when soils are too acidic?

The acids can be partially neutralized by an alkaline substance such as lime. Because lime speeds up the decomposition of organic matter in the soil, however, manure of another organic fertilizer should be added to manage soil fertility.

What determines soil permeability?

The average size of the spaces or pores in a soil.

Rock cycle

The interaction of processes that change rock types from one type to another.

What is the magnitude of an earthquake?

The measure of the amount of energy released in the earthquake, as indicated by the amplitude (size) of the vibrations when they reach a recording instrument (seismograph).

Soil erosion

The movement of soil components, especially surface litter and top soil, from one place to another. It results in the build up of sediments and sedimentary rock on land and in bodies of water.

Where are most transform faults?

The ocean floor.

What is the focus of an earthquake?

The point of initial movement.

What is the epicenter of an earthquake?

The point on the surface directly above the focus.

Erosion

The process by which materials is (1) dissolved, loosened, or worn away from one part of the earth's surface and (2) deposited in other places.

Soil permeability

The rate at which water and air move from upper to lower soil layers.

What determines soil texture?

The relative amounts of the different sizes and types of mineral particles.

*The widespread use of commercial inorganic fertilizers, especially on sloped land near streams and lakes, also causes water pollution as nitrate (N03) and phosphate (P04) fertilizer nutrients are washed into nearby bodies of water. --- > Result

The resulting plant nutrient enrichment (cultural eutrophication) causes algae blooms that use up oxygen dissolved in the water, killing fish. Rainwater seeping through the soil can also leach nitrates in commercial fertilizers into groundwater. Drinking water drawn from wells containing high levels of nitrate ions can be toxic, especially for infants, and can cause bladder cancer.

Tectonic plates

The rigid plates that are moved by the flows of energy and heated materials in the mantle convection cells. These plates are about 100 kl (60 m) thick. They are composed of the continental and oceanic crust and the rigid, outermost part of the mantle (above the atmosphere), a combination called the lithosphere.

What happens in these two upper layers?

The roots of most plants and most of a soil's organic matter are concentrated here.

What happens in undisturbed vegetated ecosystems?

The roots of plants help anchor the soil, and usually soil is not lost faster than it forms.

Geology

The science devoted to the study of these dynamic processes.

As these plates move constantly, what are they supported by?

The slowly moving asthenosphere like large pieces of ice floating on the surface of a lake.

What does the color of topsoil tell us? Give examples.

The soil's usefulness for growing crops. Ex: Dark brown/black topsoil: Nitrogen-rich and high in organic matter. Gray, bright yellow, or red topsoil: Low in organic matter and need nitrogen enrichment to support most crops.

Plate tectonics

The theory explaining the movements of the plates and the processes that occur at their boundaries.

What do these insects and creatures do?

They break down some complex organic compounds into simpler inorganic compounds soluble in water.

What did the Nature Conservancy do for farmers in Indiana?

They gave them money to but no-till equipment in exchange for a promise to use conservation tilling for at least 3 years.

What do internal processes do?

They generally build up the earth's surface.

What do farmers often do to their soil?

They often apply large amounts of irrigation water to leach salts deeper into the soil.

What do geologists do?

They study and analyze rocks and the features and processes of the earth's interior and surface.

What do external processes do?

They tend to wear down the earth's surface and produce a variety of landforms and environments formed by the buildup of eroded sediment.

How can desertification feed on itself?

Through positive feedback.

Land Classification

To ID easily erodible (marginal) land that should be neither planted in crops nor cleared of vegetation.