Rocks and the Rock Cycle

Did you know that rocks can be recycled? Not in the way that we recycle paper or cans, of course, but in a different way. Over time, processes on the earth change rocks from one form to another, and then back again. These forms can be put into three groups: Metamorphic, Sedimentary, and Igneous.

Metamorphic rock is rock that has completely been changed from its first form due to the process of the rock cycle.

Sedimentary rock is rock that has been pressed together and composed from bits of sediment, including animal and plant materials.

Igneous rock is rock that is formed from the cooling and hardening of magma and includes granite and basalt, two very common rocks that can probably be found in your yard right now next to your metal sheds or outside your log cabins.

The changes that rocks go through is called the rock cycle, and it goes something like this: The earth pushes rocks up to the surface, where they go through changes caused by erosion, the weather, and compacting. Erosion refers to the process of water breaking down rock over time. The weather, including sunlight, also causes rocks to break down. Compaction, on the other hand, is when accumulated sediment is pressed together to form sedimentary rock. Usually, this happens when sediment flows into a river or other body of water. The pressure of the water "squeezes" the sediment together, compacting it.

Eventually, these forces press the rocks back down into the earth, where they are heated by pressure within the earth. The intense pressure and heat underground presses the rocks together and, over time, can melt them into magma. Some of that magma may reach the surface, where it cools off and becomes solid, igneous rock again!

To see a great interactive chart that illustrates the process of the rock cycle, visit Learner.org.

Another animated chart that illustrates how rocks are recycled over millions of years can be seen at Widows.ucar.edu"

Visit Classzone.com to see a video of the rock cycle created by Houghton-Mifflin publishing to accompany the lessons in their science textbook.

Young elementary students can learn about the rock cycle from Rocky the Rock at The Learning Zone.

Minoscam.org has a great chart that will help you tell if your rock is Metamorphic, Sedimentary, or Igneous.

Visit IGSIndiana.edu for a list of activities you can do to learn about the rock cycle, such as making cooling crystals, exploring molten magic and making your own sandstone.

Crush and reconstruct your own rock by following the directions listed in this activity from Thinkquest.org.

Play the rock cycle game! Go to the Geology Online Museumto find out how.

Dig deeply into the rock cycle by going on a webquest created by Tony's Webquests.

Teachers, visit Geology.com for a complete list of lesson plans centered around rocks and the rock cycle.