WeatheringWeathering

What is Mechanical What is Mechanical Weathering?Weathering?

Mechanical weathering takes place when rocks are broken down without any change in the chemical nature of the rocks. The rocks are essentially torn apart by physical force, rather than by chemical breakdown.

The Wind -- Mechanical Weathering in Action!

The tree roots will expand, becoming sources of mechanical weathering.

Wave action (mechanical weathering) 

Frost wedging is a form of mechanical weathering (that is, weathering that involves physical, rather than chemical change). Frost wedging is caused by the repeated freeze-thaw cycle of water in extreme climates.

Mechanical Weathering

Mushroom Rock was carved by blowing sand.

What is Chemical What is Chemical Weathering?Weathering?

Rounded boulders like these reflect long-term erosion of granitic rocks by frost wedging and chemical weathering.

This sort of weathering is common along many coastlines and probably results from deposition of salt in cracks (salt wedging).

A wooden post that soaked for many years in a pool of brine

The grotesque swelling of the wood results from deposition of salts in the wood.

In the desert many rocks take on a dark coating of manganese oxides known as desert varnish. Native Americans inscribed petroglyphs on these rocks by scraping away the varnish, exposing lighter rock beneath. Coso volcanic field, California.

Chemical reactions break down the bonds holding the rocks together, causing them to fall apart, forming smaller and smaller pieces.

Cliff Chemical Weathering

Coastal Chemical Weathering