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Internal Forces of Change. Types of Boundaries. Convergent Come together Divergent 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
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Types of Boundaries • Convergent • Come together • Divergent • 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!
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
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
Wind Erosion • Caused by the movement of dust, sand and soil. Can create loess, a fertile soil carried by wind. • Ex. Great Plains
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