Internal Forces of Change
Types of Boundaries Convergent Divergent Transform Come together Pull apart Transform Slide past each other http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html
Convergent Boundaries Subduction One plate dives beneath another Forms volcanic mountains Accretion As one plate slides beneath another, a trench is formed Overriding plate scrapes off the subducted plate, leveling off undersea mountains and ridges Folding Two continental plates collide, forming mountains
Divergent Boundaries Spreading Two sea plates pull apart Magma rises, creating ridges or undersea mountain ranges (“new” land)
Transform Boundaries Fault Crack in earth’s surface where two plates can slide past one another When plates make a sudden, violent shift, earthquake!
External Forces of Change
Weathering Definition: The breaking down of rocks on the earth’s surface into smaller pieces. Different from erosion! No movement
Physical Weathering Caused by heat, water, ice, or pressure
Frost Wedging
Frost Heaving
Plant Roots
Burrowing of Animals
Temperature Changes
Acid rain has eaten away this limestone statue. Chemical Weathering Caused by chemical reactions. Can be caused by water, carbon dioxide, oxygen, acid rain 1908 to 1969 Acid rain has eaten away this limestone statue.
Water Water weathers rock by dissolving it
Oxygen Iron combines with oxygen in the presence of water in a processes called oxidation The product of oxidation is rust
Acid Rain Burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering
Erosion Definition: The process by which water, ice, wind or gravity moves pieces of rock and soil Different from weathering! Movement
Water Erosion Caused by fast-moving water such as rain, rivers, streams and oceans. Can eventually form a canyon or cliff (ocean). Ex. Grand Canyon
Water Erosion
Wind Erosion Caused by the movement of dust, sand and soil. Can create loess, a fertile soil carried by wind. Ex. Great Plains
Wind Erosion
Glacial (Ice) Erosion Caused by large pieces of ice moving across the earth’s surface. Can leave behind moraines (large piles of rock and debris). Ex. Rocky Mountains
Glacial Erosion