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Rocks Classifying Rocks Igneous Rocks Sedimentary Rocks Rocks from Reefs Metamorphic Rocks The Rock Cycle Table of Contents
Rocks
Classifying Rocks
Igneous Rocks
Sedimentary Rocks
Rocks from Reefs
Metamorphic Rocks
The Rock Cycle
Table of Contents
Rocks
How Rocks Form
Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock.
- Classifying Rocks
Rocks
Asking QuestionsBefore 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.
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.
Question Answer
- Classifying Rocks
Rocks
End of Section:Classifying
Rocks
Rocks
Classifying Igneous Rocks
Igneous rocks are classified according to their origin, texture, and mineral composition.
- Igneous Rocks
Rocks
Mineral Mixture
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.
- Igneous Rocks
Rocks
Mineral Mixture
Feldspar
Reading Graphs:
What mineral is most abundant in granite?
- Igneous Rocks
Rocks
Mineral Mixture
10%
Reading Graphs:
About what percentage of granite is made up of dark minerals?
- Igneous Rocks
Rocks
Mineral Mixture
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?
- Igneous Rocks
Rocks
Mineral Mixture
The overall color would be darker.
Predicting:
How would the color of the granite change if it contained less feldspar and more mica and hornblende?
- Igneous Rocks
Rocks
Detail Detail Detail
Main Idea
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.
Igneous rocks are classified by origin, texture, and composition.
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.
- Igneous Rocks
Identifying Main Ideas
Rocks
Links on Igneous Rocks
Click the SciLinks button for links on igneous rocks.
- Igneous Rocks
Rocks
End of Section:Igneous Rocks
Rocks
From Sediment to Rock
Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.
- Sedimentary Rocks
Rocks
OutliningAs you read, make an outline about sedimentary rocks. Use the red headings for the main topics and the blue headings for the subtopics.
Sedimentary Rocks
I. From Sediment to RockA. ErosionB. DepositionC. CompactionD. Cementation
II. Types of Sedimentary RockA. Clastic RocksB. Organic RocksC. Chemical Rocks
III. Uses of Sedimentary RocksA. Building MaterialsB. Tools
- Sedimentary Rocks
Rocks
Links on Sedimentary Rocks
Click the SciLinks button for links on sedimentary rocks.
- Sedimentary Rocks
Rocks
End of Section:Sedimentary
Rocks
Rocks
What You Know
What You Learned
Using Prior KnowledgeBefore 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.
1. Coral reefs grow in the oceans.2. Florida has coral reefs.3. Oceans used to be where there is dry land now.
1. Coral animals cannot live below 40 meters.2. In the United States, only the coasts of Florida and Hawaii have coral
reefs.3. Some limestone deposits on land formed from ancient reefs.
- Rocks From Reefs
Rocks
More on Coral Landforms
Click the PHSchool.com button for an activityabout coral landforms.
- Rocks From Reefs
Rocks
End of Section:Rocks From
Reefs
Rocks
Previewing VisualsBefore 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.
- Metamorphic Rocks
Rocks
Links on Metamorphic Rocks
Click the SciLinks button for links on metamorphic rocks.
- Metamorphic Rocks
Rocks
End of Section:Metamorphic
Rocks
Rocks
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.
- The Rock Cycle
Rocks
Rock Cycle Activity
Click the Active Art button to open a browser window and access Active Art about the rock cycle.
- The Rock Cycle
Rocks
Magma
Rock Cycle
SequencingAs 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.
Igneous
Sedimentary
Metamorphic
- The Rock Cycle
Rocks
End of Section:The Rock Cycle
Rocks
Rocks
Sedimentary
includeinclude include
can be
IntrusiveNon-
foliatedClastic
Graphic Organizer
Igneous Metamorphic
Extrusive Organic Chemical Foliated
Rocks
End of Section:Graphic Organizer
