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Vocab Notes. Weathering and Erosion. Chemical Weathering. Rocks broken down by reacting with gases, water, and solutions Chemical reactions break down the bonds holding rocks together, causing them to fall apart Happens in almost all rock types
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Vocab Notes Weathering and Erosion
Chemical Weathering • Rocks broken down by reacting with gases, water, and solutions • Chemical reactions break down the bonds holding rocks together, causing them to fall apart • Happens in almost all rock types • Smaller rocks = more surface area=more susceptible • More water and warmer temps= better for this weathering • http://library.thinkquest.org/20035/chemical.htm • http://facstaff.gpc.edu/~pgore/geology/geo101/weather.htm • http://www.kidsgeo.com/geology-for-kids/0067-chemical-weathering.php • Ex: rust on metal in soil, soil becomes red- brown to red. (oxidation)
Mechanical Weathering • is the process by which rocks are gradually broken into smaller pieces down without changing their chemical composition • Only shape and size changed • http://library.thinkquest.org/20035/chemical.htm • Ex: stream grinding at the bank Root wedging fracture in granite
Surface Area A rock that has been broken up has more surface area and can therefore be weathered more quickly • How much exposed area a surface has
Exfoliation • Rock peeling off in sheets rather than weathering grain by grain • Can be in paper thin sheets or large slabs • http://geology.about.com/library/bl/images/blexfoliation.htm Ex: Yosemite Valley, CA Exfoliating in thick slabs.
Frost Wedging • Type of mechanical weathering caused by the repeated freeze/thaw cycle of water • http://estes.on-line.com/rmnp/articles/frstwdg.html Process • Rainwater falls into the joints (cracks) • Temp cools w/ night • Water becomes ice and expands • Pressure put on joints • If it is too much, the joint will expand • After several freeze and thaws, the joint cracks
Oxidation • Chemical reaction of oxygen with other substances • Ex) Iron in rocks and minerals readily combines w/ oxygen forming minerals with oxidized form of iron • Ex) green copper penny, freshly cut apple turning brown, rust
Acid Precipitation • Caused by oxidation of sulfur dioxide and nitrogen oxides released by human activities • Process • Sulfur dioxide from burning of fossil fuels & nitrogen oxides from motor-vehicle exhaust • Gases combine with oxygen and water in the atmosphere • Forms sulfuric and nitric acids • Gets into water system and falls as acid rain • Effects • Soil health – wipes out some microbes and essential nutrients and minerals • organisms ph levels • Weathering of buildings and statues • Speeds up natural weathering
Erosion • The removal and transport of weathered material • Ex) running water carries weathered materials, glaciers carve out an area and take materials elsewhere (gravity helps both processes) • Also wind and organisms http://facstaff.gpc.edu/~pgore/Earth&Space/erosion.html (good site)
Deposition • Materials being dropped in another location • Final stage of erosional process • Ex) rivers emptying into large body of water and depositing sediments = delta • Ocean currents repeatedly pick up and deposit sand along a shoreline
Gully Erosion http://www.iirr.org/saem/page84-92.htm • Removal of soil by running water along deep and wide channels • Ex) can be more than 3m deep. Can present major problems to farms
http://www.ipm.iastate.edu/ipm/icm/2001/5-21-2001/preventeros.htmlhttp://www.ipm.iastate.edu/ipm/icm/2001/5-21-2001/preventeros.html Rill Erosion • Erosion by running water in small channels on the side of a slope • Can form gully erosion • Repairing • Tillage, however it makes looser • Discing • Preventing • Terraces • Contour farming • Keep high level of residue (reduces soil detachment)
