The Rock Cycle
On this website, you will learn about sedimentary, igneous, and metamorphic rocks and how they form.
Igneous Rocks
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The rock cycle is a process that continues forever. In the rock cycle, rocks are created, changed from one form to another, destroyed, and then formed again.
The rock cycle is a process that continues forever. In the rock cycle, rocks are created, changed from one form to another, destroyed, and then formed again.
Igneous
There are two types of igneous rocks. One of them is extrusive rocks. Extrusive rocks form from lava that has been erupted onto Earth's surface. Examples of extrusive rocks are basalt, andesite, and rhyolite. The other type of igneous rock is intrusive rocks. Intrusive rocks are formed when magma hardens beneath the Earth's surface. Some examples of intrusive rocks are granite, pegmatite, and peridotite. Intrusive and extrusive rocks are the origin of an igneous rock. There are different textures that an igneous rock can have. One texture is fine-grained and it is usually an extrusive rock with small crystals. Another texture of an igneous rock is coarse-grained and is usually an intrusive rock with large crystals. An igneous rock can also have a glassy texture. When an igneous rock has a glassy texture it is because magma or lava cooled really fast and the rock formed very small crystals. The last texture an igneous rock can have is a porphyritic texture. When an igneous rock has a porphyritic texture it is an intrusive rock that has cooled in two stages. In the first stage the magma begins to cool very slowly and forms large crystals. In the second stage the remaining magma cools quickly forming small crystals.
These images are from http://geology.com/rocks/igneous-rocks.shtml
Sedimentary
Sedimentary rocks are formed from sediment. Sediment is small, solid grains, mud, and pebbles. There are four steps that create sedimentary rock. The first step is erosion and in this step destructive forces, such as heat, cold, rain, waves, and grinding ice, break up and wear away the rocks on the Earth's surface. The second step is deposition and in this step, sediment settles out of the water or wind carrying it. The third step is compaction and in this step sediments are pressed together. The last step for sedimentary rocks to form is cementation. In this step dissolved minerals crystallize and glue particles of sediment together. There are three different types of sedimentary rock. The first type is clastic rock. A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together. Examples of clastic rocks are shale and sandstone. The second type of sedimentary rock is organic rock. Organic rock is sedimentary rock that forms out of remains plants and animals that are deposited in thick layers. Examples of organic rocks are coal and limestone. The last type of sedimentary rock is chemical rock. Chemical rocks form when minerals dissolve in a solution and crystallize. Examples of chemical rocks are gypsum and a type of limestone that forms from dissolved calcite.
Metamorphic
Heat and pressure can change any rock into a metamorphic rock. It can form out of igneous, sedimentary or other metamorphic rock. Metamorphic rock can form from collisions between Earth's plates when the plates push the rock down towards the heat of the mantle. Metamorphic rocks can also form from pockets of magma rising through the crust. Geologists classify metamorphic rocks by the arrangement of their grains. The igneous rock, granite, changes into the metamorphic rock, gneiss. The sedimentary rock, shale, turns into the metamorphic rock, slate. The sedimentary rock, sandstone, transforms, into the metamorphic rock, quartzite.
Here are some videos about the rock cycle http://www.youtube.com/watch?v=53lMdHzvGCQ http://www.youtube.com/watch?v=lE3jR_RhxO4