What is Weathering?
[[File:Abiskorock.JPG|thumb|200px|A rock in Abisko,Sweden fractured along existing joint geology joints possibly by frost weathering or thermal stress]] [[File:Weathering Limestone State College PA.jpg|thumb|right|comparison of unweathered (left) and weathered (right) limestone]] '''Weathering''' is the breaking down of [[Rock (geology) |rocks]], soil and their minerals through direct contact with the Earth's atmosphere, waters, or living things. It is a natural process. Weathering occurs in one place with little or no movement, and should not be confused with erosion which is when rocks and minerals are moved to another place by ice, water, wind or gravity. == Mechanical weathering == Mechanical or physical weathering is when the rocks and minerals are broken down but the [[chemical composition]] remains the same. Mechanical weathering physically breaks up rock. === Wind === Wind can blow water or small particles such as sand against the rock thus breaking it down. === Rain === Rain is another force that works slowly. The force of raindrops on some rocks make them wear down. Rain also can make a [[chemical]] change in some rocks, because it is usually slightly [[acid rain|acidic]]. The water mixes with the [[mineral]]s in the rock to break it down. === Temperature === [[File:Weathering freeze thaw action iceland.jpg|thumb|right|200px|Freeze-thaw weathering of a rock in southern [[Iceland]]]] Changing temperature can make a rock crack. Every day when the sun shines on the rock, its surface is heated. Heat causes the surface to expand (get bigger) a little. The inside of the rock, though, does not heat up as fast as the outside of the rock. The inside of the rock stays cooler. At night, the surface cools down and contracts. The expanding and contracting makes some places on the surface weak, and a crack is made. Also, if [[water]] gets into a crack in a rock and the temperature goes below the freezing point, the water will freeze and expand. After some time, the rock may be weak enough to break into piece