Weathering and Soil Formation l Weathering l The

Weathering and Soil Formation

l Weathering l The process by which rock materials are broken down by the action of physical or chemical processes.

l Mechanical Weathering l The breakdown of rock into smaller pieces by physical means. Agents include ice, wind, water, gravity, plants, and even animals.

Mechanical Agents l Ice wedging is when water seeps into cracks and then freezes. This expands the water pushing it against the sides of the crack making it wider. (Causes a lot of problems with northern states roads).

Mechanical Agents l Abrasion l The grinding and wearing away of rock through the mechanical action of other rock or sand particles.

Mechanical Agents l Water l rocks flowing down a stream bump into each other, causing them to become round and smooth.

Mechanical Agents l Wind l Sand silt blown against a rock can wear away at the surface.

Mechanical Agents l Gravity l As rocks fall and roll down a mountainside.

Mechanical Agents l Plants l Tree roots grow into cracks and force the crack to widen.

Mechanical Agents l Animals l Any type of burrowing animal causes mechanical weathering. Examples include ants, worms, mice, coyotes, rabbits, moles, prarie dogs, insects, and gophers.

l Chemical Weathering l Rocks breaking down due to chemical reactions.

Chemical Agents l Water causes some materials to dissolve or go into solution with the water. (salts/sugar)

Chemical Agents l Acid Precipitation l Acids from precipitation can dissolve rocks (limestone in vinegar).

Living things l Lichens l Cause a chemical reaction that slowly breaks down the rock. l Animals l Animal waste can be acidic which can slowly wear away a rock. (bats)

Air l Oxidation l An element combines with oxygen to form an oxide.

Differential Weathering l Process by which softer, less weather resistant rocks wear away and leave harder, more weather resistant rock behind.