The Rock Cycle

The Rock Cycle

By Mrs. Lorbacher

Introduction of the Coaches

Click on each of the coaches below and let them introduce themselves to you! They will appear on pages of this book to help you with comprehension, understanding the science topic, and to give you some cool facts!

What is a rock?

A rock is a naturally occuring substance that is made of two or more minerals.

We see rocks everyday! They occur naturally in nature and you may notice them in places like the mountains or in stream beds (as well as many, many other places!).

Rocks are also used by people everyday. You may see them used to construct buildings and bridges. Additionally, people use them to decorate the outsides of buildings as well as to make items for inside their homes like granite countertops.

What's in a rock?

Rocks are made of minerals . Minerals look very similar to rocks but they are actually different. So how do you know if something is a mineral and not a rock... let's find out!

1. Like rocks, minerals are a naturally occuring substance or in other words, they cannot be man-made.

2. They are inorganic , which means that they are not living. This is also a property of rocks.

3. Minerals are crystalline solids - the atoms that they are made up have repeated patterns that you could see under a very strong microscope. Basically, minerals look the same all the way through which is why we call them a specimen or a sample and not a rock.

4. Minerals have definite chemical compositions- they are one substance where as a rock could be many substances (minerals) bunched into one bundle.

Not all rocks are created equally...

Unlike the US Declaration of Independence, rocks are not created equally. But what does that mean? Well, we do know that rocks are made of many types of minerals, so that makes them different from each other. But, geologists also have separated these different types of rocks into bigger categories by how they are formed over millions of years. Read on to find out about Sedimentary, Metamorphic, and Igneous rocks!

Sedimentary Rocks

Sedimentary rocks are made of bits of small rocks, fragments, organic materials such as plants or animal remains. These pieces are called sediment .

Over millions of years, these sediments are compacted and cemented into sedimentary rocks .

Igneous Rocks

Igenous means "made from heat or fire." This perfectly describes how igneous rocks  are made. Rocks are melted in the extreme temperatures over 100 miles under the surface of the Earth. When a rock is liquid and under the Earth, it is called magma . Igneous rocks are made when magma cools. 

There are two ways for magma to cool and as a result, two types of igneous rocks: 

1. Intrusive Igenous Rocks  : magma cools before it can get to the Earth's surface. It cools very slowly and is very hard. These rocks usually have large crystals.

2. Extrusive Igneous Rocks : the magma erupts from the volcano and becomes lava on the Earth's surface. Air and moisture cools the lava quickly. These rocks usually have smaller crystals, if any at all, because they cool so rapidly.

Metamorphic Rocks

The name for this type of rock comes from the word "metamorphosis," which means an obvious change of form. This is the perfect way to describe metamorphic rocks because they change shape and composition rather dramatically.

Metamorphic rocks are formed deep under the Earth's surface. The intense heat and pressure from other rocks above can change their shape and/or chemical make-up. They are made from igenous, sedimentary, and other metamorphic rocks.

How are rocks made?

Now that we know a little more about the three types of rocks, let's talk about how they are made. All the rocks on and in the Earth have been there since the formation of the Earth. So really, rocks aren't made but rather are changed from one form to another.

Geologists  have found that there is a cycle in which rocks are changed, which is called The Rock Cycle. 

There are five processes which change rocks: 

1. Heat and Pressure
2. Melting
3. Cooling
4. Weathering and Erosion
5. Compacting and Cementing

The second part of this book will explore these different processes and their part of the rock cycle.

Heat and Pressure

Many miles under the Earth's surface, the heat is so intense that it begins to melt solid rocks. However, before rocks get completely to the melting point, they may change shape from one form to another without melting.

Additionally, the weight of millions of tons of rocks overhead put a lot of pressure on rocks many miles below the Earth's surface. The heat and pressure work together to change the rocks in this process, which is called metamorphism .

Metamorphic rocks are formed this way from igenous and sedimentary rocks.

Melting

Extreme temperatures deep under the Earth's surface can melt solid rocks. Molten rock is called magma .  Metamorphic and igenous rocks can be melted and changed into magma.

Cooling

Liquid rock, or magma , turns into a solid (rock) when it is cooled. As we learned earlier, igneous rocks are formed from cooled magma.

Magma cools in two different ways:

1. The magma rises from deep inside the Earth and explodes from a volcano. The lava cools quickly from the air and moisture. The resulting rock is an extrusive igneous rock.

2. The magma is pushed slowly toward Earth's surface over thousands or even millions of years. It gradually cools to form intrusive igneous rocks underneath the surface.

Weathering and Erosion

Wind, rain, sun, running water, and temperature changes wear away at rocks over millions of years. These elements break down big rocks, like mountains, into little pieces of rocks and sand. These little pieces are called sediments . After a while, these sediments run into rivers, streams, and oceans.

Compacting and Cementing

As sediments begin to pile up, their weight puts a lot of pressure on the sediments on the bottom. This extreme pressure starts to gradually push the sediments together, or compact them.

Minerals  also act as a type of cement to help bond the different sediments together. Over a long period of time, these sediments are compacted and cemented into sedimentary rocks  .  

If you want to know more...

Books

The Rock Factory: The Story of the Rock Cycle. By Jacqui Bailey. Mankato, MN: Picture Window Books, 2006.

What is the Rock Cycle? (Let's Rock!). By Natalie Hyde. New York: Crabtree Publishing Company, 2010.

Websites

• Geology for kids: http://www.kidsgeo.com/geology-for-kids/
• How do rocks undergo change?: http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page01.cfm

Interactives

• Follow a rock through its journey in the rock cycle: http://www.phschool.com/atschool/phsciexp/active_art/rock_cycle/index.html
• In depth look of the rock cycle processes with animations: http://www.learner.org/interactives/rockcycle/
• Test your knowledge of the rock cycle processes: http://www.kscience.co.uk/animations/rock_cycle.htm

Sources

Content

Rock Cycle (2010). Retrieved Oct. 26, 2010, from Annenberg Media, Washington, D.C.. Web site: http://www.learner.org/interactives/rockcycle/.

Photographs

• [Compacting and cementing]. Retrieved November 7, 2010, from: 

  http://www.learner.org/interactives/rockcycle/change3.html

• [Cooling]. Retrieved November 7, 2010, from: 

  http://www.isaacsondesign-hosting.com/bridgettej/rockcycle/rocks.html 

• [Cover page rock cycle diagram]. Retrieved October 26 , 2010, from: http://www.rocksandminerals4u.com/rock_cycle.html.
• [Detailed rock cycle diagram]. Retrieved November 1, 2010, from: 

  http://www.cotf.edu/ete/modules/everglades/FEwetlands1.html

• [Heat and pressure]. Retrieved November 7, 2010, from: 

  http://www.isaacsondesign-hosting.com/bridgettej/rockcycle/metamorphic_rock.html

• [Marble]. Retrieved November 7, 2010, from: 

  http://www.minimegeology.com/home/mgeo/page_73_22/marble_metamorphic_rock.html

• [Melting]. Retrieved November 7, 2010, from: 

  http://www.learner.org/interactives/rockcycle/change2.html

• [Lava erupting from volcano]. Retrieved November 7, 2010, from:  

  http://www.schools.utah.gov/curr/science/sciber00/8th/earth/sciber/rocks2.htm

• Lorbacher, K. (Photographer). Large rock at Linville Falls [photograph].
• [Rocks and minerals placemat]. Retrieved November 2, 2010, from: 

  http://www.painlesslearning.com/html/placemats/rocks.htm

• [Sandstone]. Retrieved November 1, 2010, from: http://www.beg.utexas.edu/mainweb/publications/graphics/sandstone.htm

•  [Untitled photograph of feldspar]. Retrieved October 26, 2010, from: http://www.mii.org/Minerals/photofeldspar.html

• [Utah Sandstone]. Retrieved November 1, 2010, from:  http://www.moorlandschool.co.uk/earth/rockcycle.htm

• [Weathering and erosion]. Retrieved November 7, 2010, from: 

  http://www.greenwichschools.org/page.cfm?p=2967