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Weathering Natural process
that breaks down rock into sediment (sand, silt, clay)
Begins the process of forming soil from rock and sediment.
Affects sediment particle size and soil texture.
Mechanical Weathering
Burrowing AnimalsIce WedgingPlant RootsWindWater
Physical process that breaks down rock but does not change the composition of rock.
Mechanical Weathering Ice wedging is
the process that occurs when water freezes, expands and thaws in the cracks of a rock
Overtime the cracks will get wider and deeper and the rock will break
Plant growth causes rock to break by roots exerting pressure on the rock
Plant roots can seek their way into rock cracks and continue to grow creating pressure in the cracks of rock.
Mechanical Weathering Burrowing
animals dig tunnels in the ground loosening small rocks and sediment and eventually pushing them to the surface
Wind carries other sediment and potentially beat on the surface of other rock loosening or breaking other rock
Water can exert pressure on sediment and small rock thereby further breaking the rock.
Chemical Weathering
Chemical process that breaks down rock by chemical reactions that dissolve minerals or change them into different minerals.
Rock composition will change!
Carbonic acid Natural plant acids Oxidation Acid rain
Chemical Weathering-Natural Acids
Carbonic acid forms when water reacts w/ carbon dioxide gas in the air.
Carbonic acid is a weak acid that can dissolve some minerals found in rock.
Carbonic acid dissolves calcite a mineral found in limestone
Ex: cave formation Other natural acids
can dissolve the mineral feldspar which is found in granite, some types of sandstone and other rocks.
Kaolinite is a clay mineral found in some soil and is formed from dissolved (broken down) feldspar.
Chemical Weathering-Plant Acids and Oxidation
Plant roots give off acids
These acids can dissolve some minerals found in rock making the rock weak and causing the rock to break into smaller pieces
Oxidation occurs when oxygen gas and moisture react with certain materials to form a new material
This new material looks like rust.
Oxidation of minerals gives some rock a red or rust color
Effects of Climate and Rock Type
Climate affects the rate (how fast) weathering occurs
Cold, polar climates increases MECHANCAL weathering
Warm, wet climates increases CHEMICAL weathering
Desert climate slows CHEMICAL weathering
Cold, polar climates slows CHEMICAL weathering
For Additional Information:See the Glencoe textbook. You may access the textbook online via the ARMS website. • Click on Academics• Click on Science
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