The Rock Cycle
It Totally Rocks!
What is the Rock Cycle?
Magma, Crystallization & Igneous Rocks
Igneous rocks are rocks formed from magma or lava. There are two main types of igneous rocks: extrusive igneous rocks and intrusive igneous rocks. Intrusive igneous rocks are rocks that form from cooled magma under the Earth's surface. These rocks cool slowly, which result in the formation of large crystals. Examples of this type of rock include granite and diorite. Extrusive igneous rocks are rocks that form from lava, magma that has been brought to the surface of the Earth. Since the molten rock is more exposed on the surface of the Earth, it cools more quickly. This results in smaller crystals. Examples of this type of igneous rock include basalt and obsidian.
Erosion, Sediment & Sedimentary Rocks
- Water seeping into the cracks of a rock and expanding when it freezes.
- Temperature changes, causing the rock to expand and contract.
- The growth of salt crystals over time (the salt is left behind after saltwater evaporates).
- Plant roots and animals breaking the rocks apart.
Chemical weathering is when chemical reactions take place in order to break down a rock. For example, when carbon dioxide and water combine, it creates carbonic acid. This weak acid can dissolve rocks. In fact, limestone caves owe their existence to carbonic acid (which is really good at dissolving limestone).
After being weathered away, bits and pieces of rock are carried away by water, ice, gravity and, or wind. This process is known as erosion. These particles settle down and are deposited as sediment.
Over time, the sediment accumulates and becomes sedimentary rock. This type of rock can be classified into three groups: clastic sedimentary rocks, chemical sedimentary rocks and organic sedimentary rock. Clastic sedimentary rocks are made up of bits and pieces of mechanically weathered debris. Sandstone and conglomerate (above right) is a good example. Chemical sedimentary rocks are made up of pieces of chemically weathered rocks. Flint is an example of this type of rock. Finally, organic sedimentary rocks are made up of accumulated plant and animal debris. Limestone is an example of an organic sedimentary rock.
One cool thing about sedimentary rock is that fossils can be found in it. In fact, paleontologists (scientists who study fossils) most commonly find fossils in this type of rock.
Rock Cycle Music Video
"Earth Floor: Cycles." Earth Floor: Cycles. The Exploring the Environment Project. Web. 14 Feb. 2016.
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"Metamorphic Rocks." Geology.com. Geology.com. Web. 14 Feb. 2016. <http://geology.com/rocks/metamorphic-rocks.shtml>.
"Sedimentary Rocks." Geology.com. Geology.com. Web. 14 Feb. 2016. <http://geology.com/rocks/sedimentary-rocks.shtml>.
"The Rock Cycle." The Rock Cycle. Mineralology4Kids. Web. 14 Feb. 2016. <http://www.mineralogy4kids.org/rock-cycle>.
"Weathering." National Geographic Education. National Geographic Society, 2011. Web. 14 Feb. 2016. <http://education.nationalgeographic.org/encyclopedia/weathering/>.