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What Causes Sedimentary And Igneous Rocks To Change?

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There are many different processes which cause rocks to change, most are to do with the environment and happen over a long period of time. In fact, all rocks change from one type to another over time, again and again; this is known as the rock cycle.

Igneous and metamorphic rocks change to sedimentary rocks through uplift to the Earth’s surface, weathering and erosion, transportation, deposition and cementation. The process which produces igneous rocks from sedimentary and metamorphic is melting and cooling.  The other process involved in this rock cycle is the process of exposure to heat and/or pressure, which results in rocks changing into metamorphic rocks.

Sedimentary rocks make up about three-quarters of the rocks at the Earth’s surface. They form at the surface in environments such as beaches, rivers, the ocean and anywhere that sand, mud, and other types of sediment collect.

Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.

The final type of rocks, metamorphic are formed when Earth movements cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. They do not melt, but the minerals they contain are changed chemically, forming metamorphic rocks.

Many people think that rocks don’t change, for example, if you find a chunk of granite today, can you expect that it will still be granite at the end of your lifetime? Well while this may well be true, it is only because our lifetimes are very short in relation to the history of the Earth. When we look back millions of years, we can see examples of how rocks change from one to another, and do so continually.

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