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Rocks from Reefs Metamorphic Rocks The Rock Cycle

How Rocks Form - Classifying Rocks
Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock.

Before you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions. Question Answer What does a rock’s color tell you? It can provide clues about the rock’s mineral and chemical composition. How do geologists describe a rock’s texture? Geologists use terms based on the size, shape, and patterns of the grains.

End of Section: Classifying Rocks

Classifying Igneous Rocks
Igneous rocks are classified according to their origin, texture, and mineral composition.

Mineral Mixture - Igneous Rocks
Granite is a mixture of light-colored minerals, such as feldspar and quartz, and dark-colored minerals, including hornblende and different types of mica. But granite can vary in mineral composition. This affects its color and texture. Study the circle graph and then answer the questions.

Mineral Mixture - Igneous Rocks Reading Graphs:
What mineral is most abundant in granite? Feldspar

Mineral Mixture - Igneous Rocks Reading Graphs:
About what percentage of granite is made up of dark minerals? 10%

Mineral Mixture - Igneous Rocks 100% - (35% + 10%) = 55% Calculating:
If the amount of quartz increases to 35 percent and the amount of dark-colored minerals stays the same, what percentage of the granite will be made up of feldspar? 100% - (35% + 10%) = 55%

Mineral Mixture - Igneous Rocks Predicting:
How would the color of the granite change if it contained less feldspar and more mica and hornblende? The overall color would be darker.

Identifying Main Ideas
- Igneous Rocks Identifying Main Ideas As you read the section “Classifying Igneous Rocks,” write the main idea in a graphic organizer like the one below. Then write three supporting details. The supporting details further explain the main idea. Main Idea Igneous rocks are classified by origin, texture, and composition. Detail Detail Detail Extrusive rock forms from lava on the surface; intrusive rock forms from magma from beneath the surface. Intrusive rocks have larger crystals than extrusive rocks because they cool more slowly. High-silica rocks are light colored; low-silica rocks are dark colored.

End of Section: Igneous Rocks

From Sediment to Rock - Sedimentary Rocks
Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

Outlining - Sedimentary Rocks
As you read, make an outline about sedimentary rocks. Use the red headings for the main topics and the blue headings for the subtopics. From Sediment to Rock Erosion Deposition Compaction Cementation Types of Sedimentary Rock Clastic Rocks Organic Rocks Chemical Rocks Uses of Sedimentary Rocks Building Materials Tools

End of Section: Sedimentary Rocks

Using Prior Knowledge - Rocks From Reefs
Before you read, look at the section headings and visuals to see what this section is about. Then write what you know about coral reefs in a graphic organizer like the one below. As you read, write what you learn. What You Know Coral reefs grow in the oceans. Florida has coral reefs. Oceans used to be where there is dry land now. What You Learned Coral animals cannot live below 40 meters. In the United States, only the coasts of Florida and Hawaii have coral reefs. Some limestone deposits on land formed from ancient reefs.

More on Coral Landforms
- Rocks From Reefs More on Coral Landforms Click the PHSchool.com button for an activity about coral landforms.

End of Section: Rocks From Reefs

Previewing Visuals - Metamorphic Rocks
Before you read, preview Figure 17. Then write two questions that you have about metamorphic rocks in a graphic organizer like the one below. As you read, answer your questions. Previewing Q. Why do the crystals in gneiss line up in bands? A. Gneiss is a type of metamorphic rock that is foliated—the crystals are flattened to form parallel lines. Q. How does quartzite form from sandstone? A. High temperature and pressure on the minerals in sandstone cause them to be changed into minerals that make up quartzite.

End of Section: Metamorphic Rocks

A Cycle of Many Pathways
- The Rock Cycle A Cycle of Many Pathways Forces deep inside Earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust.

Rock Cycle Activity - The Rock Cycle
Click the Active Art button to open a browser window and access Active Art about the rock cycle.

Sequencing - The Rock Cycle
As you read, make a cycle diagram that shows stages in the rock cycle. Write each stage of the rock cycle in a separate circle in your diagram. Metamorphic Igneous Sedimentary

End of Section: The Rock Cycle

Graphic Organizer Igneous Metamorphic Extrusive Organic Chemical
Foliated

End of Section: Graphic Organizer