Transcript Chapter 5: Rocks

CHAPTER 5: ROCKS
Section 1: Classifying Rocks
WHAT ARE ROCKS MADE OF?
Rocks are mixtures of minerals and other
materials.
 Some contain only a single mineral; others
contain several minerals (ex. granite = quartz +
feldspar + hornblende + mica)
 Rock-forming minerals: approx. 20 common
minerals that make up most of the rocks of
Earth’s crust

LECTURE CHECK 1

Question: What are rocks made of?
LECTURE CHECK 1
Question: What are rocks made of?
 Answer: Mixtures of minerals and other
materials

MINERAL COMPOSITION AND COLOR

Color provides clues to the rock’s mineral
composition
Granite: light-colored rock with high silica content
 Basalt: dark-colored rock with low silica content

Shape and color of crystals
 Tests used to identify minerals (e.g. acid test)

LECTURE CHECK 2

Question: How is silica content related to color?
LECTURE CHECK 2
Question: How is silica content related to color?
 Answer: High-silica content is associated with
lighter color and low-silica content is associated
with darker color.

TEXTURE
Texture: look and feel of the rock’s surface
 Grain: particles of minerals or other rocks, which
give the rock its texture

Size: coarse, fine
 Shape: rounded, jagged
 Pattern: banded, nonbanded

LECTURE CHECK 3

Question: What are the three things that you can
observe about grain?
LECTURE CHECK 3
Question: What are the three things that you can
observe about grain?
 Answer: size, shape, and pattern

CLASSIFYING ROCKS

Geologists must use color, composition, texture,
and other tests to classify and identify rocks.
HOW ROCKS FORM

Three groups of rocks based on origin
Igneous: form from cooling of magma or lava
 Sedimentary: form when particles of other rocks or the remains of
plants and animals are pressed and cemented together; layers buried
below the surface
 Metamorphic: form when an existing rock is changed by heat,
pressure, or chemical reactions; most deep underground

LECTURE CHECK 4

Question: Limestone forms on the ocean floor in
tropical environments. What type of rock do you
think limestone is?
LECTURE CHECK 4
Question: Limestone forms on the ocean floor in
tropical environments. What type of rock do you
think limestone is?
 Answer: sedimentary

POST-LESSON QUIZ
1. What type of rock is formed when an existing
rock is changed by intense heat and pressure
deep underground?
a. sedimentary
b. igneous
c. metamorphic
d. mineral
POST-LESSON QUIZ
2. What type of rock is formed from magma or lava
cooling?
a. sedimentary
b. igneous
c. metamorphic
d. mineral
POST-LESSON QUIZ
3. What type of rock forms when particles of other
rocks or the remains of plants and animals are
pressed and cemented together?
a. sedimentary
b. igneous
c. metamorphic
d. mineral
POST-LESSON QUIZ
4. What term describes the look or feel of a rock’s
surface?
a. texture
b. grain
c. density
d. mass
POST-LESSON QUIZ
5. Which is not a characteristic that can be used to
identify rocks?
a. color
b. crystal shape
c. reaction to acid
d. size of rock