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Idea Transcript
Ch 21 Section 1 Weathering and Soil
Weathering The process of physical or chemical breakdown of material at or near Earth’s surface. Interaction of water, air and rock over time.
Factors that influence weathering:
Water Air Nature of material being weathered Climate Time
Mechanical weathering Changing big material into small material. Forces that cause mechanical weathering are expansion or contraction of materials and biological effects.
Prying Rock apart When water freezes it expands. If water freezes
while in rock it will force the rock apart and spit it. Frost weathering
As rocks fall off cliffs they can impact other rocks and break them apart. Impact agents
Chemical weathering Process of chemicals interacting with material then forming new material during a chemical reaction. Water and oxygen are the key components to chemical weathering.
Soil mixture of weathered rock, organic matter, water, and air that is capable of supporting plant life.
Soil is the end product of weathering.
O and A layers are
considered top soil. (where plants get most of their nutrients)
E- where finer
sediments and soluble materials settle down.
B- collects the
materials from above and is usually darker than the upper layers.
C- partially crumbled and weathered bedrock.
R- unweathered bedrock.
Soil types Soil is separated according to composition and physical properties. Amount of precipitation Temperature range Vegetation present
Soil conservation Soil depletion can occur when over planting takes
place. Plants use up nutrients from soil and when farmers don’t replenish the nutrients the soil will become useless.
Farmers can correct the soil depletion by adding fertilizers.
Soil erosion can take place if the vegetation is removed or because the land is too steep. Deforestation or soil on a hill.