Key Terms
weathering - any of the chemical or mechanical processes by which rocks exposed
to the weather undergo changes in character and break down
mechanical weathering - any of the destructive effects of the atmosphere and
the exposure of rocks to the extremes of the surface
chemical weathering - chemical effects of water, carbon dioxide, and oxygen
attacking and destroying the minerals that are near the surface of the Earth
frost wedging - a collective term for several mechanical weathering processes
induced by stresses created by the freezing of water into ice
exfoliation - the sheeting of rocks and their disintegration, thought to be due to
thermal expansion, at least on small structures
oxidation - the absorption by a mineral of one or more oxygen ions. The major
type of chemical weathering, particularly in rocks containing iron
acid rain - acid precipitation falling as rain
weathering rates - a measurement of the amount of weathering over a given
time period
surface area - measurement of the extent of the area covered by a surface
topography - detailed, precise description of a place or region
climate - the meteorological conditions, including temperature, precipitation, and
wind, that characteristically prevail in a particular region
soil - the top layer of the Earth's surface, consisting or rock and mineral particles
mixed with organic matter
soil profile - the vertical section of soil showing the nature and sequence of the
various layers, as developed by deposition or weathering, or both
soil horizon - a layer of soil, approximately horizontal, which differs in structure
and composition from the adjacent layers
humus - the amorphous, ordinarily dark colored, colloidal matter in soil; a complex
of the fractions of organic matter of plant, animal, and microbial origin that are
most resistant to decomposition
regolith - the layer of loose rock resting on bedrock, constituting the surface of
most land
parent bedrock - the original rock from which something else was formed
deposition - the dropping of material which has been picked up and transported by
wind, water, or ice
erosion - a group of natural processes, including weathering, dissolution, abrasion,
corrosion, and transportation, by which material is worn away from the Earth's
surface
rill erosion - the formation of numerous, closely spaced rills due to the uneven
removal of surface soil by stream-lets of running water
gully erosion - erosion of soil by running water
wave erosion - erosion of the ocean floor by sediment moved by ocean waves
glacial erosion - movement of soil or rock from one point to another by the action
of the moving ice of a glacier
dust bowl - a region reduced to aridity by drought and dust storms
mass movement - the movement downslope of rock fragments and soil under the
influence of gravity
slides - a form of mass movement in which material slides in a relatively straight
plane
flows - the mass movement of material held in suspension by water
creeps - the slow movement of rock debris and soil down a weathered slope
abrasion - the process of wearing down or rubbing away by means of friction
deflation - the erosion of soil by the wind
ventifact - a stone that has been shaped, polished, or faceted by wind-driven sand
deforestation - the act process of removing trees from or clearing a forest
erosion - a group of natural processes, including weathering, dissolution, abrasion,
corrosion, and transportation, by which material is worn away from the Earth's
surface
tillage erosion - erosion that moves soil from the top of the field downward,
exposing subsoil at the crest while burying soil at the bottom
contour farming - cultivation of land along lines connecting points of equal
elevation, to prevent water erosion
slash and burn - a form of agriculture in which an area of forest is cleared by
cutting and burning, and is then planted, usually for several seasons, before being
left to return to forest
fallowing - plowed but left unseeded during a growing season
soil conservation - management of soil to prevent or reduce soil erosion and
depletion by wind and water
terracing - a method of shaping land to control erosion on slopes of rolling land
used for cropping and other purposes
strip cropping - the growing of a cultivated crop, such as cotton, and a sodforming crop, such as alfalfa, in alternating strips following the contour of the land,
in order to minimize erosion
contour plowing - farming practice of plowing across a slope following its
elevation contour lines
no-till farming - cultivation technique in which the soil is disturbed only along the
slit or hole into which seeds are planted
wind breaks - a hedge, fence, or row of trees serving to lessen or break the force
of the wind
ground cover - a low-growing dense growth of plants planted to prevent soil
erosion in areas where turf is difficult to grow, as in deep shade, or on a steep slope