Contact: firstname.lastname@example.org Rocks Made By: Amy Barker
Rocks In this lesson you will learn about the rock cycle and what some kinds of rocks there are on Earth. First thing we will begin with is identifying the three main different kinds of rocks. Below are three different kinds of rocks. Using what you already know about rocks, can you determine what kind is which?
The three main types of rocks are Igneous, Metamorphic, and Sedimentary. Igneous rocks are made from volcanic material. Metamorphic rocks are rocks that were something else but have been changed. Sedimentary rocks are made of small particles of rock. This rock is called an obsidian. It is an example of an igneous rock. This metamorphic rock is called gneiss. Limestone is considered a sedimentary rock.
Believe it or not, but all of these kinds of rocks are related. Their relationship to one another is called The Rock Cycle. Study the picture and see how one type of rock can be changed to another kind.
Igneous Rocks The formation of igneous rocks depends solely on magma. As you can see from this diagram, an oceanic plate drives itself underneath the continental plate. This is called a fault. The oceanic plate is more dense than the continental plate making it go underneath the lighter continental plate. The oceanic plate activates the zone of magma generation, causing it to come up through the Earth’s crust and create a volcano. The magma that reaches the surface is called lava, and when it cools, it forms igneous rock.
As you can see from this picture, not all of the magma, called the batholith in this picture, reaches the surface. Some of it remains in dikes, sills, and laccoliths. This magma then cools over a long period of time and becomes igneous rock also. For more information about the formation of igneous rocks, go to Igneous Rock Formation
Here are some examples of igneous rocks. This igneous rock is called basalt. It is generally found on the surface of the Earth, composed of cooled lava. Granite is a common form of igneous rock found. Below is a picture of Granite in a close-up view.
Metamorphic Rocks Metamorphic rocks are rocks that were once of one kind but because of heat, pressure, or a chemical change, they were changed into something else. These rocks are called metamorphic rocks because they are “morphed,” or changed to a different kind of rock. The rocks could have been either igneous, sedimentary, or even another metamorphic rock to begin with. This rock is called granite. It is an igneous rock. Because of heat and pressure, it can be changed to a metamorphic rock called marble. This is what becomes Of granite when it is “morphed.” This is marble. This is a close-up of a section of marble rock.
A common way for metamorphic rocks to form is by the help of the formation of igneous rocks. When igneous rock is hot magma, the rock surrounding this magma heats up also. This rock will become very hot and will change because of the heat and pressure. When it cools, it will no longer be exactly like what it was originally. It will have changed to metamorphic rock. This is a conglomerate rock. It was formed from heat and pressure and turned into a metamorphic rock. This “morphed” rock is called quartz.
Chemical changes also can create metamorphic rock. This happens when very hot fluids fill the pores of existing rock because of heat and intense pressure. The fluids can cause chemical reactions to occur. Over time, these chemical reactions can change what the rock is made up of. The result is a new metamorphic rock. Slate is a commonly found metamorphic rock. It has been used for chalk boards and gravestones, but because it has a tendency to crack over time with exposure to water, other rock materials are used in replace of slate today.
For more information on the formation of metamorphic rocks, go to Metamorphic Rock Formation
Sedimentary Rocks Sedimentary rocks are made from other rocks that have been weathered. Weathering is the breaking down of rock pieces into smaller pieces. These small pieces of rock are then cemented together, compacted tightly, crystallized again to form new sedimentary rock. This is a close-up view of sandstone, a type of sedimentary rock. Notice the different colored particles that this rock is made up of. This gives the impression that it is made up of many different kinds of rock that have been broken down into small pieces and have been compacted tightly together.
Sedimentary rocks are often formed in layers. This occurs because the rocks were formed underwater. A river or stream picks up sediment along its path. When the river or stream drains into a large body of water, the sediment falls to the floor and accumulates. Different kinds of sediment are carried downstream at different times. This causes layers of different colored particles to accumulate.
Coal is made of buried leaves, plants, and other organic material. Where coal is found makes scientists believe that there was plant growth in the past. This is an example of a fossiliferous rock. This simply means that fossils are present in this sedimentary rock. Four different types of sedimentary rock are fossiliferous, coal, shale, and sandstone. Sandstone is formed by sand that could have been weathered by the wind or could have accumulated in part of a river bottom. This sedimentary rock is called shale. It is formed by mud, which gives us the impression that it was part of a river or lake bottom in the past.
This is called a conglomerate rock that is classified as sedimentary. For more information on the formation of sedimentary rock, go to Sedimentary Rock Formation
Today you have learned about the rock cycle and some information about igneous, metamorphic, and sedimentary rocks. Use what you know about rocks and go out into the world and see if you can identify what kind of rocks are where.
Now that you have learned a little about the rock cycle and the different rocks found on Earth, complete the rock worksheet provided. Remember, if you get stuck on a question, you can always go back in the presentation and look for the answers. The answer key is also provided when you finish the worksheet. Good luck! Rock Worksheet The Answers
For the Teacher Below are some links to various web sites that may be helpful in making a more complete lesson on the rock cycle. • Activities for the Classroom • More Information on Igneous Rocks • More Information on Metamorphic Rocks • More Information on Sedimentary Rocks