Magma creates igneous rocks
Beneath the surface of the Earth, temperatures become hot enough to melt rocks into magma. When the magma reaches the surface, it is known as lava. Cooling of either magma or lava crystallizes the minerals inside, forming igneous rocks. Intrusive rocks, such as granite, form from magma below the surface cooling slowly to create larger crystals. Extrusive igneous rocks result from lava, which cooled quickly at or near the Earth's surface. These rocks have small crystals in their structure. Common extrusive igneous rocks include obsidian and basalt.
Erosion and Weathering
All types of rocks undergo weathering, which breaks the rock down into small particles. These create sediment and soil, more commonly known as dirt. When water combines with the dirt, it becomes mud. These sediments forms sedimentary rocks.
Formation of Sedimentary Rocks
Over time, the sediments become pressed and cemented together to create sedimentary rocks. Sedimentary rocks do not have a pure composition. Their ingredients come from the particles resulting from weathering of igneous, metamorphic and other sedimentary rocks. These particles are known as clasts. Clasts can form sandstone, conglomerate and breccia rocks.
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Metamorphic rocks change igneous, sedimentary or other metamorphic rocks through intense pressure from the weight of the Earth's crust on top of the rocks. This pressure generates heat, which can alter the chemical composition of the rocks. Marble, mica and quartzite form through metamorphosis. Metamorphic rock needs temperatures of 300 to 700 degrees Celsius to form.
Melting and Subduction
Geologic movements of the tectonic plates in the crust push all types of rocks beneath the surface. This movement also creates heat. Once under the surface, the temperatures melt the rock to once again become magma where it waits to begin the rock cycle process again.