Mountains are subject to different types of weathering.
Weathering is an important part of the rock cycle, the never-ending process that breaks down and recycles the rocks of the earth's crust. Igneous rock forms in Earth's mantle and becomes part of the crust. At the planet's surface, igneous and metamorphic rock is weathered into sediment that compacts into sedimentary stone.
Weathering
Weathering is a natural process that breaks down mountains and individual rocks into small mineral particles. It's part of the phenomenon of erosion. Rocks that are formed far under the Earth's surface in its mantle are exposed to different conditions at the planet's surface. These forces of nature disintegrate rocks into stable minerals or cause them to transform into different minerals. Surface weathering turns solid rock into soil and is also responsible for moving the soil around.
Mechanical Weathering
Mechanical weathering is the physical breaking down of rocks into smaller stones of the same chemical composition. This type of weathering occurs by the abrasive actions of wind-borne or waterborne grains of sand or other hard mineral particles. Ice splits rock by a process called frost wedging. Water seeps into cracks and fissures then cracks the rock when it expands after freezing. The rock exfoliates into sheets or leaves that split off along joints running parallel to the ground.
Chemical Weathering
Chemical weathering occurs when rocks are dissolved or decomposed by chemical reactions. The reactions produce smaller rock particles with changed chemical makeups. A good example of chemical weathering is when slightly acidic rainwater reacts with and dissolves carbonate rocks such as limestone, dolomite and marble. Oxidation or reaction with oxygen is another cause of rock degradation. Hydrolysis and hydration are other rock-breaking types of chemical weathering caused by exchange reactions between water and mineral ions.
Biological Weathering
Biological weathering is when living organisms help break rock into sediments or soil. Tree and plant roots growing into rock joints and fissures weaken and cause the rock to split along its seams. Biological weathering happens through chemical and physical means. Acids produced by lichens, fungi and microorganisms etch and slowly break down rock. Decomposing organic debris releases carbon that reacts with water and atmospheric gases to create carbonic acids that decompose rocks and boulders.
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