Download Scott Foresman Science

Name ______________________________
Lesson 3 Summary
Use with pp. 208–213
Lesson 3: How are rocks classified?
Vocabulary
igneous type of rock that forms from molten rock
sedimentary type of rock that forms when layers of sediments settle on
top of one another and harden
metamorphic type of rock formed when heat and pressure change the
properties of rock
Rocks are classified by how they form, or
are made. Below Earth’s surface, rocks get
so hot that they become melted, or molten.
Molten rock is called magma. Igneous
rocks are made from magma. Igneous rocks
are usually hard. They do not have layers.
They often have crystals that interlock, or
fit together.
Magma erupts to Earth’s surface through
volcanoes. When molten rock reaches the
surface, it is called lava.
Magma Cooling Quickly
On Earth’s surface, lava cools quickly.
Some igneous rocks are made from lava
that cools quickly. These rocks have small
crystals. Pumice and basalt are rocks that
form when lava cools quickly.
Magma Cooling Slowly
Some igneous rocks are made below
Earth’s surface. Magma below Earth’s
surface cools very slowly. The magma
forms igneous rocks with large crystals.
Granite is an igneous rock. It forms
when magma cools slowly. Granite has
large crystals of quartz, feldspar, and mica.
Granite is very hard.
Sedimentary Rocks
Sediments are made of soil, shells, small
pieces of rock, and dead plant and animal
matter. Water, wind, ice, and gravity can
move sediments from one place to another.
Sediments settle and gather on the bottoms
40 Chapter 6, Lesson 3 Summary
of rivers, lakes, and oceans. Sedimentary
rocks form when layers of sediments settle
on top of each other. The weight of the
layers pushes the sediments together. Sticky
clay minerals also hold the sediments
together. The layers gradually get harder
and form rocks.
The layers on top are usually the newest,
and the layers on the bottom are the oldest.
This means that fossils in a lower layer of
rock are older than fossils in a higher layer.
Sedimentary rocks are usually soft and
have layers. They are made of different
sediments. Limestone is made of the shells
of tiny sea animals that lived long ago.
Metamorphic Rock
It is very hot inside the Earth. There
is also a lot of pressure. The rocks above
squeeze and press on the rocks below.
The heat and pressure together can
change the properties of rocks. This makes
metamorphic rocks. Metamorphic rocks
can be made from sedimentary rocks,
igneous rocks, or other metamorphic rocks.
The heat and pressure can change the
crystals in a rock. The crystals can be a
different size or shape. Sometimes new
minerals form.
Metamorphic rocks are usually hard.
They can break into flat sheets or slabs.
Slate is a metamorphic rock with thin
layers.
Intervention Study Guide
© Pearson Education, Inc. 4
Igneous Rocks
Name ______________________________
Lesson 3 Questions
Use with pp. 208–213
Lesson 3 Questions
1. What are the three types of rocks?
2. What are igneous rocks made from?
3. What is limestone made of? What type of rock is limestone?
© Pearson Education, Inc. 4
4. What is one example of a metamorphic rock?
Intervention Study Guide
Chapter 6, Lesson 3 Questions 41