Physical and Chemical Weathering of Rocks

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Rocks found on the surface of the Earth undergo a process over time call weathering. Weathering is the breaking down of rock material. There are two main types of weathering: physical and weathering. Physical, or mechanical, weathering happens when rock is broken through the force of another substance on the rock such as ice, running water, wind, or plant growth. Chemical weathering occurs when reactions between rock and another substance dissolve the rock, causing parts of it to fall away.

Here are some examples of physical and chemical weathering of rocks.

Physical Weather Examples

Water movement is a major force in physical weathering. The persistent crash of waves against rocks causes physical weathering.


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Physical weathering by waves at Arcadia National Park in Maine.  Photo: John J. Mosesso, USGS. Public domain.
Physical weathering by waves at Arcadia National Park in Maine. Photo: John J. Mosesso, USGS. Public domain.

When water seeps into rocks and freezes, it expands and causes the rock to crack.

Horsetail Falls, Columbia River Gorge.  Photo: USDA, public domain
Horsetail Falls, Columbia River Gorge. Photo: USDA, public domain

These mushroom-shaped rock pinnacles in Goblin State Park, Utah are formed by wind weathering the sandstone.

Goblin Valley State Park.  Photo: Ian D. Keating, CC BY 2.0
Goblin Valley State Park. Photo: Ian D. Keating, CC BY 2.0

Roots from plants grow into rocks, cracking the rocks and causing weathering.

Precambrian metamorphic rock wall in Lamar Canyon. Yellowstone National Park, Photo: Jim Peaco, NPS, public domain
Precambrian metamorphic rock wall in Lamar Canyon. Yellowstone National Park, Photo: Jim Peaco, NPS, public domain

The honeycomb weathering seen in this photo from Utah is likely caused by physical weathering.

Honeycombs, Utah Utah Geological Survey, Public Domain
Honeycombs, Utah. Photo: Utah Geological Survey, Public Domain

Chemical Weathering Examples

Chemical weathering can been seen in this photo of Blue Basin located in the John Day National Monument in Oregon. The green color of the claystone is from by chemical weathering of a mineral called celadonite.

Blue Basin, Oregon Bonnie Moreland, public domain
Blue Basin, Oregon. Photo: Bonnie Moreland, public domain

Chemical weathering is, in part, responsible for the colorful oxidation of metals such as mica, iron, and manganese at Artist’s Palette in Death Valley.

Artist's Palette, Death Valley.  Photo: Paxson Woelber, CC BY 2.0
Artist’s Palette, Death Valley. Photo: Paxson Woelber, CC BY 2.0

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