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Weathering and erosion

Weathering is the process where rock Larry is dissolved, worn away or broken down into smaller and smaller pieces. There are mechanical, chemical and organic weathering processes.

Tree roots breaking up bedrock. North Yorkshire moors, Yorkshire, England. © Richard Burt

Organic weathering happens when plants break up rocks with their growing roots or plant acids help dissolve rock.

Once the rock has been weakened and broken up by weathering it is ready for erosion. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity.

Flat benches called terraces (covered with bright green plants) formed as the river eroded layers of mud and ash.  Mount St. Helens, Washington, USA. © Andy Bajc

Frost shattered rock.  Half Moon Island, South Shetland Islands, Antarctica. © Richard Burt
Frost shattered bricks in Ontario, Canada. © Abigail Burt

Mechanical weathering physically breaks up rock. One example is called frost action or frost shattering. Water gets into cracks and joints in bedrock. When the water freezes it expands and the cracks are opened a little wider. Over time pieces of rock can split off a rock face and big boulders are broken into smaller rocks and gravel.

This process can also break up bricks on buildings.

Rainwater is a very weak acid.  It can dissolve limestone and other carbonate rocks leaving behind pits and holes.  Wied-iz-zurrieq, Malta. © Richard Burt

Chemical weathering decomposes or decays rocks and minerals. An example of chemical weathering is waterWilliam dissolving limestone.

When ice melts or wind and water William slow down they can't carry as much sediment. The sediment is dropped, or deposited, in landforms.

Little Langdale Tarn and the Coniston Fells.


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