Weathering and Erosion
Weathering The breakdown of rock material by physical and chemical processes.
Physical Weathering Process by which rocks are broken down into smaller pieces by physical changes. Causes of physical weathering include: –Changes in temperature –Pressure changes –Actions of plant and animals –Water –Wind and Gravity
Temperature Change Changes in temperature can cause a rock to break apart. A decrease in temperature can cause a rock to contract and a rise in temperature can cause a rock to expand. Ice wedging can cause rocks to physically break apart when water collects in the cracks of rocks and the temperature drops
Ice Wedging
Pressure Change Physical weathering can be caused by pressure changes. Rocks formed under pressure deep within earth can become exposed at the surface and changes in pressure can cause layers of rock to separate. Exfoliation- the process by which the outer layers of rock slowly peel away due to pressure changes.
Pressure Change
Effects of Animals on Weathering Many animals dig burrows into the ground, allowing for more rock to become exposed Common burrowing animals include: -Ground squirrels -Prairie Dogs -Ants -Earthworms
Burrowing of Animals
Wind, Water, and Gravity Abrasion- the breaking down and wearing away of rock material by the mechanical action of other rocks. Wind- the small particles carried by wind hit the surface of rocks and slowly wear them away Water- moves rocks causing them to collide with other rocks Gravity-can cause landslides where large rocks can fall from above and break more rocks below.
Water Erosion Rivers, streams, and runoff
Plant Growth The roots of plants can grow in small cracks in rocks causing the rock to expand due to the increase in pressure.
Plant Growth
Chemical Weathering The process that breaks down rock through chemical reactions. The agents of chemical weathering –Water –Oxygen –Carbon dioxide –Living organisms –Acid rain
Erosion The process by which water, ice, wind or gravity moves fragments of rock and soil.
Oxygen Iron combines with oxygen in the presence of water in a processes called oxidation The product of oxidation is rust
Water Water weathers rock by dissolving it
Wind Erosion
Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering
Reactions with Acids in Groundwater As groundwater moves through spaces or cracks in rock, acids in the water can cause rocks to dissolve. A small crack in a rock can result in the formation of extensive cave systems that are carved out over time.
Reactions with Acids in Groundwater
Caves
Living Organisms Lichens and mosses can grow on rocks and produce weak acids that chemically weather rock
Sinkholes