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Home >Review
So you've looked through all of the pages on this site, you've read the information, you've done the activities. What have you learned? Here's a review of some of the major points that you should take away from this experience:
Rocks
There are three main rock types (sedimentary, igneous, and metamorphic).
Any one of these types can become any other type through the processes
of the rock cycle (weathering and erosion, cementation and compaction,
cooling and solidification or crystallization, heat and pressure or metamorphism,
melting). There are two intermediary steps in the process (sediment and
magma).
1. Sedimentary rocks are formed from preexisting rocks through
the processes of weathering and erosion, which creates sediment, and the
cementation and compaction of that sediment.
2 types:
Chemical--formed from minerals that have been dissolved, or chemical sediment
Detrital--formed from preexisting rock fragments and organic material, or detrital sediment.
2. Igneous rocks are formed from preexisting rocks through the
processes of melting, which creates magma, and the cooling and solidification
of that magma. Recooling and solidification is also known as crystallization.
2 types:
Intrusive--formed from the slow cooling of magma underground. These rocks have large crystals.
Extrusive--formed from the quick cooling of lava aboveground. These rocks have very small crystals.
3. Metamorphic rocks are formed from preexisting rocks through the process of metamorphism, where rocks undergo extreme heat and pressure.
2 types:
Foliated--formed from a mica-rich rock undergoing increasingly great amounts of heat and pressure. These rocks have many visible layers and tend to flake off. Shale is an example of a Foliated Metamorphic rock.
Non-foliated--usually formed when a preexisting rock is touched by hot magma and is recrystallized, but does not get hot enough to melt.
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Processes
There
are five main processes that make up the
rock cycle.
1. Metamorphism means "changed form." It is the process that changes sedimentary, igneous, and metamorphic rocks into new metamorphic rocks.
2. Weathering and Erosion is the process by which rocks are attacked by the environment. There are two types of weathering, mechanical and chemical. Mechanical weathering is simply breaking the rock down into smaller fragments. This process forms detrital sedimentary rocks. Chemical weathering occurs when chemical reactions alter the composition of a rock. The chemical sediment that forms from this type of erosion forms chemical sedimentary rocks.
3. Cementation and Compaction is a two step process. Rocks are constantly be deposited on top of each other. As these layers begin to build on top of each other, they begin to compress. This is the process of compaction.
4. Melting is takes place under the surface of the earth. This kind of rock is called liquid rock or magma.
5. Cooling and Solidification is the process of lava cooling on the surface of the earth. The rocks formed from this process have small crystals (Extrusive Igneous Rocks).
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The Rock Cycle Web Site
© 2000
Webmasters: Chris
Lucas and Kate Seigfried
If you have any questions or comments, please feel free to email us.
This page was last updated on December 4, 2000
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