weathering: breaking down of rock can be mechanical or chemical

mechanical: rock broken down into smaller pieces by physical processes does NOT change the chemical composition of rock ***same minerals***

main agents of mechanical weathering are: ice gravity and plants and animals

frost wedging: water seeps into cracks then freezes puts pressure on rock until it breaks (ice)

exfoliation: rock breaks into curved sheets that peel away from the rock due to a release of pressure from overlying rock (called unloading) as rain has loosened the layers (water)

organic activity: mechanical weathering by a living organism plant roots grow into rock cracks then break the rock as the roots grow larger

animals dig and burrow to break rock earthworms bring small fragments to the surface which weathers them quicker

***removes OR changes the types of minerals*** chemical: rock broken down by chemical processes changes the composition of rock ***removes OR changes the types of minerals***

water carbon dioxide oxygen main agents of chemical weathering are: and oxygen

water is the main agent by absorbing or dissolving other materials that affect the rocks any minerals dissolved in the water are moved elsewhere

this is how limestone weathers when carbon dioxide from air dissolves in water, it forms carbonic acid this is how limestone weathers

oxygen combines with water to cause the outer layer of rock to look darker in color (oxidation = rust!)

chemical weathering can change the physical shape of rock water seeps into cracks (called joints) first this weathers the corners and edges of rock more rapidly so gets a rounded look

is called spheroidal weathering joint NOT exfoliation because minerals have changed

all rocks don’t weather in the same way differential weathering: where different parts of a large rock mass weather at different rates

Shoals’ Jug Rock!

rock composition rocks with softer minerals (like calcite) = faster weathering rocks with harder minerals (like quartz) = slower weathering

surface area more surface area (fractures, joints, smaller pieces) = faster weathering less surface area (larger pieces) = slower weathering

climate alternating periods of hot & cold weather = faster weathering humid (wet) weather = faster weathering