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Physical weathering

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Physical weathering is the actual breaking down of rock by the action of natural forces such as water, men, plants and animals. But how do these forces wear down rock? Here we see trees growing out of what appears to be a solid granite rock. Actually the roots are penetrating tiny cracks in the rock as the trees continue to grow their roots will further extend and enlarge the cracks eventually fragmenting the rock just as these roots have done to this rock. Probably the most common cause of physical weathering is due to the constant freezing and thawing of water in and around the rocks themselves. Let’s take a look at a simple experiment which shows how liquid water expands when it turns to solid ice. We fill this plastic measuring cup with water up to the top mark. We wanna make sure that we use a plastic container and not a glass container. We now take our cup of water and place it in the freezer. Here it will sit undisturbed for several hours. Later when we view the cup we find that the water has turned to ice and that it is expanded almost ten percent. We know that it is increased in sides both upward and outward and has actually cracked the plastic cap. But how does freezing water affect rocks? Water frequently collects on rocks and gets into these small openings when temperatures drop below freezing, the water in these cracks turns to ice and expands. This exerts a tremendous amount of pressure on the openings in these rocks. As temperatures rise and the ice melts back into its liquid form it creeps deeper into the fractures When the water freezes again it further expands the openings in the rock. This cycle will go on day after day, year after year until finally a once huge mount side could disintegrate to a pile of small rock fragments.

Video Details

Duration: 2 minutes and 39 seconds
Country: Spain
Language: English
Views: 1,446
Posted by: ang_ruiz on Sep 23, 2011

Weathering is the process which causes rocks and minerals to break down and disintegrate into smaller pieces. This is easily explained and illustrated in this video.

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