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What are igneous rocks and sedimentary rocks?
Igneous rocks are made from magma. Magma is made of melted rocks. (When it is underground it is called magma, when it erupts on the surface of the earth, it is called lava…. It's the same material though.) When magma/lava cools, it forms igneous rocks. There are many types of igneous rocks and the specific type of igneous rock can vary according to which minerals are present in the melted rock, how fast it cools, and the presence of things like water. Sedimentary rocks are made out of tiny pieces of debris. This can include tiny rocks, sand, clay, silt, and organic material. (Organic materials can vary from rotted leaves to tiny, shelled ocean creatures, or many other types of organic material.) These bits of material collect in an area, then through compaction and cementation, they stick together to form sedimentary rocks. Sedimentary rocks can also be formed when minerals are dissolved in water and are then resolidified. This type of sedimentary rock is called a chemical sedimentary rock. Oolitic limestone is a good example of this type of sedimentary rock. (MORE)
