Types of Rocks

Info about rocks


The three main types of rocks are sedimentary, metamorphic, and igneous. They are different because of the way they're formed.


Let's talk about igneous rocks first. Igneous rocks are formed when magma cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes [now it's called lava]. When lava cools very quickly, no crystals form and the rock looks shiny and like glass. Sometimes gas gets into the rock while it's cooling and makes it have holes in it. Obsidian is an example of an igneous rock.


Now, we should talk about metamorphic rocks! Metamorphic rocks are formed under the surface of the earth from the metamorphosis that occurs due to intense heat and being squeezed. The rocks that come from this process might have shiny crystals on their surface. Schist is a example of a metamorphic rock.


Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stone in the rock, and it is usually the only type that contains fossils. Limestone is an example of this rock.


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