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science chapter 6

Terms

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process of soil developing from rock
rock fractures and breaks down----plats begint o grow in the weathered rock----worms, insects, bacteria & fungi living among the plat roots add organic matter to the soil----plants and animals die & decay and form soil
erosion
a process in which topsoil & rocks are worn down through the action of water, wind and glaciers
B horizon
less humus than hor. A, contains elements leached form A hor.
desertification
when cattle and sheep eat all the grass and plants don't grow back (too little rain), the soil is blown away and the water in the ground evaporates ans the dry surface blows away
chamical weathering is more rapid in warm, wet climates and slower in
deserts and polar regions (lack moisture)
chemical weathering
when water, air and other substances react with minerals in rocks and the chemical composition of rok changes
mechanical weathering processes
growing plants, ice wedging, growing crystals, lightning, expansion & contraction with heating and cooling
leaching
the downward removal of soil mineralsdissolved in H2O
mechanical weathering
the weathering of rock without changing its chemical makeup
weathering contributes to the rock cycle by
making sediment that can form into sedimentary rocks
humus
dark colored decaying matter that provides nutrients for plants = promotes good soil structure and helps soil retain water
horizons
each layer of soil; A, B, or C.
A horizon
the top layer of soil that has most nutrients and humus, most fully evolved layer dark in color and has minerals grains, decaying leaves, roots, insects, and worms
weathering
the breaking of rock into smaller rocks
climate
the pattern of weather that occurs in a particular area over many years
chemical weathering processes
water (oxygen & hydrogen react eith chemicals in rocks & new compounds form), acids (carbonic acid reacts with calcite to dissolve rock), oxygen (oxydation occurs when a material such as iron is exposed to water & the oxygen in the air causes iron to change to rust)
soil profile
the different layers of soil
soil
material on the surface of the earth on which plants grow. It is produced by weathering rocks
soil is a mixture of
weathered rock, organic matter, mineral fragments, water, air = can support vegitation
C horizon
bottom layer, least evolved layer, contains minerals leached from B hor., contains partly weathered rock and solid rock at the bottom

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