The Earth's surface is constantly changing from a process called weathering. Weathering occurs over time and there are several agents that are responsible for changing the surface. Mechanical weathering is when the rock at or near the earth's surface is physically weakened. Large masses are chunked into smaller pieces, producing stones, pebbles, sand, soil and dust. This can occur from water freezing in the crack of a rock or possibly when seeds take root in the crack of a rock. Chemical weathering changes the actual chemistry of the rock, splitting them or carving out crevices and holes. During chemical weathering, the chemical makeup of a rock changes the minerals or combines with new chemical elements. Water and carbon dioxide are the two most important factors. Acid rain is one type of chemical weathering which destroys forests, pollutes water, and eats away at rock formations and buildings.
Erosion can also change the structure of the land surface by moving weathered material such as gravel, soil, and sand. Without erosion, though, the earth would be a barren rock without soil; so erosion, as long as it is natural, can be a good thing for the environment. Niagara Falls, one of the seven wonders of the world, was created by mechanical weathering, and it is a beautiful place to visit. Water, wind, and glaciers are major agents of erosion.
Extreme weather can contribute to both mechanical and chemical weathering. High winds and flooding can cause movement of rocks, soil, and sand. Vast amounts of ice melting and precipitation can chip away at rocks and cause movement, as well. With global warming at the forefront of our environmental concerns, some people question whether the extreme weather that we experience in the U.S. is due to global warming. Let's see what a NASA expert thinks.
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A man in a Hawaiian Shirt with gray hair and glasses is next to a man in a turquoise shirt. The Title “Ask a Climate Scientist” appears in white on the screen. The Man in the turquoise shirt walks away and another man comes on screen to adjust the lighting and then walks off. The name Bill Patzert appears in white letters. Bill Patzert (The man in the Hawaiian shirt with gray hair and glasses) hands papers to someone off screen and then stands and looks at the camera. |
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Bill is looking at the camera as he listens and responds to the questions. Pictures of floods, droughts, tornadoes and forest fires appear as he names them. Bill appears on camera. Picture of the polar ice caps appear. |
Question: Extreme weather was more frequent in recent years, is it a sign that global warming is gaining pace and exceeding predictions? Bill: No. Has extreme weather been more frequent in recent years? The evidence is to the contrary. The United States has always had extreme weather, when we look back on our weather history, it’s been punishing. Floods, droughts, tornadoes, hurricanes, great forest fires. Is Global Warming happening? No doubt about it. We are living in a warming world. We are living in a melting world, sea levels are rising. |
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Bill is back on camera talking Pictures of hurricanes, tornadoes, forest fires, floods and drought appear and then pan back to Bill |
Now, direct evidence of the footprint, or fingerprint of global warming, we are seeing more frequent, more intent and longer lasting heat waves. As far as hurricanes, tornadoes, forest fires, floods and drought, the evidence is not in. The consensus among almost all scientists is that it’s a small fingerprint not a large footprint. |
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But what is true is that in this country, in The United States, we live in many areas with great risk to drought, to tornadoes, to hurricanes, and so part of the dialogue is not only extreme weather, and global warming, but is the amount of risk we can tolerate. |
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Now looking to the future, global change, global warming, definitely is accelerating, and it will have an impact on extreme weather, but at this point, not much! |
Question
How can the physical process of erosion - water, wind, and glaciers - affect the landscape?
Water, wind, and glaciers act as forces of erosion, which moves weathered materials mechanically. This breaks down larger rocks into smaller ones, which allows for movement across the land.
