Weathering The wearing down of stuff

Weathering types The breaking down and changing of rocks at or near the Earth’s surface Weathering comes in two forms –Mechanical –Chemical Weathering is always occurring on Earth but many times it is too slow to be observed by humans

Mechanical Weathering Mechanical weathering occurs when physical forces break rock into smaller pieces without changing the rock chemically –This involves breaking rocks into pieces There are three major contributors to mechanical weathering

????????

Frost Wedging Ice is the largest contributor to mechanical weathering –When water freezes it expands –Water will sneak its way into small cracks in rocks and then freeze When it freezes it actually cracks the rocks –This occurs mostly at inland mid-latitude where freezing and thawing occur regularly

Unloading Sometimes large amounts of igneous rocks become exposed through uplift and other erosion of overlying rocks When this occurs the igneous rocks will sometimes “shed” it outside layers –This shedding is called exfoliation Similar to what you do with your skin

Biological activity Biological activity can pertain to any weathering or breaking down that occurs because of organisms –Tree roots may break bedrock –Animals burrowing

The other type of weathering Chemical weathering is the transformation of rock into one or more new compounds –This means that rock goes through a chemical change in chemical weathering Water is a contributor to chemical weathering –Water itself usually doesn’t react with rock, but it does absorb other chemicals that do lead to reactions

Water as a chemical weathererereererer Water many times absorbs carbon dioxide in the air This carbon dioxide in water turns into a very weak carbonic acid solution and reacts with many different minerals in rock –Oxygen reacts with metals to form rust –Marble rock is easily prone to chemical weathering

More chemical weathering Chemical weathering in granite rock causes the feldspar to turn into a more “clay” like material This clay is dissolved and swept out to sea –The remaining quartz is not as effected by chemical weathering and doesn’t make it out to sea This leaves small quartz particles to make up many beaches

Spherodial weathering Both chemical and mechanical weathering usually erode the surfaces or close to the surface of rocks –When this happens the rock generally results in a spherical shape Sharpe jagged rocks are usually not well weathered Rounded dull rocks are usually highly weathered

Rate of weathering Weathering doesn’t always occur in the same rate for every object on earth –Some factors are… Type of rocks Climate Integrity of the material being weathered

Rock Type and climate The type of rock has a major factor on how it will weather –Many igneous rocks are less prone to weathering then sedimentary and some metamorphic rocks Granite tombstone vs. marble tombstone Some climates are more prone to weathering then others –Places that have changing temperatures, humid places and pollution tend to lead to more weathering both chemically and mechanically

??????????

Integrity of materials Weathering can only occur where weathering agents like water can come in contact with the rock –If a rock is porous and cracked it will erode as faster then a rock that is not –The more surface area of a rock the faster it will erode