Types of Rocks

Sedimentary, Igneous, & Metamorphic, by Maddie Hoffmann.

                                                         Types of Rocks

Igneous Rock- Igneous rocks are formed from the solidification of molten rock material. There are two types of igneous rocks such as diorite, gabbro, granite and pegmatite which form deep beneath Earth's surface and andesite, basalt, obsidian, pumice, rhyolite and scoria which form on top of or above Earth's surface. Igneous and metamorphic rocks make up 90-95% of the Earth's surface in volume. There are more

than 700 types of igneous rocks and most were formed beneath the Earth's surface.

  Metamorphic Rock- Metamorphic rocks make up a large part of the Earth's surface. Metamorphic rocks are made by being deep under the Earth's surface, exposed to heat at high temperatures at 150-200 degrees celsius causing physical or chemical changes to the rock. There are two types of metamorphic rocks such as gneiss, phyllite, schist and slate which have a layered or banded appearance that is produced by exposure to heat and pressure. There is also marble and quartzite which do not have a layered or banded appearance.

Sedimentary Rock-  Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. The material can include minerals, small pieces of plants and other organic matter. Sedimentary rock forms layers called strata which can often be seen in exposed cliffs. Sedimentary rocks cover the majority of the Earth's rocky surface but only make up a small percentage of the Earth’s crust compared to metamorphic and igneous types of rocks.

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