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  • Rocks are everywhere! They are large and small, heavy or light, porous or dense, but rocks

  • in some shape or form can be found all over the planet. Different types of rock are formed

  • in different ways. There are three main types of rock: Igneous, Sedimentary, and Metamorphic.

  • Igneous is a word that means 'fiery.' Igneous rock is formed when magma or lava cools. Sometimes

  • magma cools slowly underneath the earth's surface. This forms intrusive igneous rock,

  • like granite. Other times lava cools when it comes to the surface in a volcanic eruption.

  • This forms extrusive igneous rock. Some examples of extrusive igneous rock are tuff, obsidian,

  • and pumice. Igneous rocks make up about 95% of the earth's crust.

  • The next type of rock is Sedimentary rock. Sediment is small particles of sand, mud,

  • and organic material that settle to the bottom of water or land areas, often lakes or oceans.

  • Sedimentary rocks are formed when sediment accumulates over time in deposits that form

  • layers. These layers become squeezed and compressed over time until they consolidate into a rock.

  • Sedimentary rocks are the types of rocks in which fossils may be found, since the process

  • of forming sedimentary rocks can preserve plant and animal remains that are deposited

  • into the sediment layers. Some examples of sedimentary rock are limestone, shale, and

  • sandstone.

  • The third type of rock is Metamorphic rock. The word 'metamorph' means to change form,

  • and metamorphic rock is rock that has been changed by extreme heat and pressure. Sedimentary

  • rock, igneous rock, or even other metamorphic rocks can be changed by heat and pressure

  • into new kinds of rock. Metamorphic rocks can be formed by being deep under the earth,

  • where pressure and temperatures are high, or when rock near the surface is heated up

  • by the movement of tectonic plates or magma. Different types of rocks become different

  • types of metamorphic rock when exposed to heat and pressure. For example, shale becomes

  • slate, sandstone becomes quartzite, and limestone becomes marble.

  • Rocks are slowly but constantly changing in something known as the 'rock cycle.' The rock

  • cycle begins with magma, or hot melted rock, deep beneath the earth's surface. This magma

  • becomes crystallized, becoming igneous rock. These rocks begin to erode, or break down

  • into small pieces because of wind, water, or other forces. The small fragments of rock

  • are carried away as sediment when water passes over them and are deposited in layers which

  • eventually become sedimentary rocks. Then, some sedimentary rocks are pushed below the

  • surface due to tectonic activity, where they are exposed to heat and pressure, transforming

  • them into metamorphic rocks. If the rocks are buried even deeper, they may melt and

  • form magma, starting the cycle all over again. Of course, sedimentary and metamorphic rocks

  • can be eroded into sediment, and igneous rock can become metamorphic rock or lava, but one

  • way or another, rocks all over the world keep changing from one form to the next.

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