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Rocks
Table of Contents
Classifying Rocks
Igneous Rocks
Sedimentary Rocks
Rocks from Reefs
Metamorphic Rocks
The Rock Cycle
Rocks
Rocks - Classifying Rocks
How Rocks Form
Geologists classify rocks into three major
groups: igneous rock, sedimentary rock,
and metamorphic rock.
Rocks - Classifying Rocks
Asking Questions
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 Geologists use terms based
a rock’s texture?
on the size, shape, and
patterns of the grains.
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End of Section:
Classifying
Rocks
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Rocks - Igneous Rocks
Mineral Mixture
Granite is a mixture of lightcolored minerals, such as
feldspar and quartz, and darkcolored 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.
Rocks - Igneous Rocks
Mineral Mixture
Reading Graphs:
What mineral is most
abundant in granite?
Feldspar
Rocks
Rocks - Igneous Rocks
Classifying Igneous Rocks
Igneous rocks can be made from either lava
and cool quickly (Extrusive) or magma
(Intrusive) and cool slowly. They are then
classified according to their origin, texture, and
mineral composition.
Label each
as intrusive
or extrusive
Rocks - Igneous Rocks
Mineral Mixture
Reading Graphs:
About what percentage of
granite is made up of dark
minerals?
10%
Rocks - Igneous Rocks
Mineral Mixture
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%
Rocks - Igneous Rocks
Mineral Mixture
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.
Rocks - 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
Extrusive rock forms
from lava on the
surface; intrusive
rock forms from
magma from beneath
the surface.
Detail
Intrusive rocks have
larger crystals than
extrusive rocks
because they cool
more slowly.
Detail
High-silica rocks are
light colored; lowsilica rocks are dark
colored.
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End of Section:
Igneous Rocks
Rocks
Rocks - Sedimentary Rocks
From Sediment to Rock
Most sedimentary rocks are formed through a series of
processes: Weathering, erosion, deposition, compaction, and
cementation. (Cementation is also known as Lithification )
Weathering – breaking
down of rocks to make
sediment. Often times
this happens due to
weather
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Metamorphic Rocks
Metamorphic rocks come from the
transformation of any existing rock types, The
original rock (protolith) is subjected to heat
(temperatures greater than 150 to 200 °C)
and pressure (1500 bars),[1] causing physical
and/or chemical changes. The beginning rock
may be sedimentary rock, igneous rock or
another older metamorphic rock (but it does
not melt completely).
Rocks - Sedimentary Rocks
Outlining
Lithification - Another
word for Cementation (the
gluing together of clastic
pieces with deposited
minerals) in sedimentary
rocks.
Sedimentary Rocks
I. From Sediment to Rock
A. Erosion
B. Deposition
C. Compaction
D. Cementation
II. Types of Sedimentary Rock
A. Clastic Rocks
B. Organic Rocks
C. Chemical Rocks
III. Uses of Sedimentary Rocks
A. Building Materials
B. Tools
Rocks
Rocks - Rocks From Reefs
Using Prior Knowledge
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
1.
2.
3.
Coral reefs grow in the oceans.
Florida has coral reefs.
Oceans used to be where there is dry land now.
What You Learned
1.
2.
3.
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.
Rocks - Metamorphic Rocks
Previewing Visuals
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.
Rocks - 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.
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Rocks - The Rock Cycle
Sequencing
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.
Rock Cycle
Magma
Metamorphic
Sedimentary
Igneous
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End of Section:
The Rock Cycle
Rocks
Graphic Organizer
Rocks
can be
Igneous
Sedimentary
Metamorphic
include
include
include
Intrusive
Extrusive
Clastic
Organic
Chemical
Foliated
Nonfoliated
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End of Section:
Graphic Organizer