How Do Rocks Change?

Lesson Plan - Get It!

Audio:

• Do you recycle some of your trash?

Recycling trash means it is changed into something else. For example, recycled plastic can be used for bottles, furniture, toys, and clothing!

Rocks and water are recycled on the earth through different cycles. Water is recycled through the water cycle, and rocks are recycled through the rock cycle.

The rock cycle constantly occurs on and below the earth's surface, as shown in the image below.

• What are the three types of rocks outlined in green in the image?
• In which direction do the arrows move?
• Why do you think the arrows move circularly?

The three types of rocks are igneous, metamorphic, and sedimentary. All rocks fall into one of these three categories and move through the rock cycle to change.

As you learn about each type, write the italicized terms in your notebook or journal on a vocabulary page.

Magma is a liquid crust found underground. It moves up toward the surface through volcanic and geologic activity.

As it reaches the surface, magma cools down and solidifies into igneous rock.

Igneous rocks can form above or below ground. Igneous rocks above ground are called extrusive igneous rocks, which cool very quickly.

When a rock cools very quickly, it makes it difficult to see the particles in the rock. Extrusive igneous rocks look the same throughout, like the rock below.

Intrusive igneous rocks form under the earth's surface and cool slowly. During the cooling process, crystals form and are easily visible.

Granite is an excellent example of an intrusive igneous rock. Notice how you can see the particles and crystals in the rock sample.

Igneous rock can be broken down during the processes of weathering and erosion to create tiny particles and sediment. Eventually, the sediment runs off and can build up in another location, forming a sedimentary rock.

Sediments can build up in layers or become cemented together quickly. Sedimentary rocks often have a sandy texture, and you can see the particles making up the rock.

• Did you know that scientists find the most fossils in sedimentary rocks?

Fossils are visible in sedimentary rocks because the organism can be preserved as layers of sediment build-up.

When sedimentary rocks are buried deep in the earth, they can be exposed to high heat and pressure. Metamorphic rocks form when sedimentary or igneous rocks interact with heat and pressure under the earth's surface.

Metamorphic rocks with visible layers are called foliated.

• What type of rock forms foliated metamorphic rocks underground?

Sedimentary rocks!

Non-foliated metamorphic rocks do not have visible layers; a great example is marble.

Marble is used in many homes for countertops because it is visually appealing and durable.

Each type of rock can be broken down and turned into a new substance through the rock cycle.

Metamorphic rocks can be weathered into small sediments that build into layers, forming a new sedimentary rock. Igneous rocks are remarkably below the earth's surface and can compact into metamorphic rocks.

Draw a picture representing the rock cycle without looking at the image at the start of the lesson! Use arrows and labels to help explain your image.

Head to the Got It? section to review the rock cycle with an online presentation.