3 7 the rocks and soils beneath us (earth science)

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Science Content

Rocks and Soil

Scott Foresman Science 3.7

ISBN 0-328-13827-4

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Vocabulary
decay
igneous rock
loam
metamorphic rock
mineral
nutrient
rock
sedimentary rock
soil

Picture Credits
Every effort has been made to secure permission and provide appropriate credit for photographic material.
The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.
Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).
Opener: Getty Images; 2 Getty Images; Backgrounds: Getty Images.
Scott Foresman/Dorling Kindersley would also like to thank: 2 (CR), 8 (CR, BC), 9 (CL, BR),
12 (CR) Natural History Museum, London/DK Images.
Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.

ISBN: 0-328-13827-4
Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America.
This publication is protected by Copyright, and permission should be obtained from the publisher prior to any
prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,
mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to
Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.
3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

What did you learn?

1. Which kind of rock forms in layers?
2. What are three ways that minerals
are described?
3. What are some ways minerals help
you to stay healthy?
4.

On page six, you
read about metamorphic rock. Write
to explain how metamorphic rock
forms from limestone, based on
by L. L. Owens
what you have read.

5.

Compare and Contrast How
does soil with a lot of clay compare
to soil with a lot of sand?


Rocks Are Everywhere

Groups of Rocks

Rocks are solid objects that come in all
different shapes and sizes. Have you ever wondered
what our planet’s rocks are made of? Rocks are
made mostly of minerals. A mineral is a natural
substance that is made of nonliving matter.

Rocks have different colors and textures
depending on the minerals in them. A rock
can be made of just one mineral
or of many different minerals.
A rock’s texture is the
size of the bits of minerals,
or grains, within it. A rock’s
color depends on the kind
of minerals and other
substances that are in the rock.

Scientists group rocks by their color, texture,
and minerals. Rocks are also grouped by how
they formed.
Igneous rock comes from a mixture of
melted minerals and gases deep inside the
ground. This blazing hot mixture cools and
hardens as it moves toward the surface. If the
solid rock cools quickly, its mineral grains can
be large. But if the solid rock cools slowly,
its mineral grains can be too small to see.
Shape, color, and
texture can indicate
rock type.

Granite

Gabbro

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Ironstone

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Obsidian

Snowflake
obsidian

One kind of igneous rock is obsidian.
Obsidian is dark, smooth, glassy, and very hard.
It forms when melted rock cools very quickly.
It can be used to make tools. Some obsidian stones
have white designs on the surface where crystals
formed. The designs look similar to snowflakes.
Those rocks are called snowflake obsidian.

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When water travels over the land, it picks up
small bits of broken rock. When these bits of
rock settle on the bottom of lakes, rivers, and
oceans, they are called sediment. Over thousands
of years, pressure can bind
bits of sediment together.
This turns the sediment
into sedimentary rock.
The remains of dead

plants and animals can be
buried under layers of
sedimentary rock. After
Fern fossil
many years, these remains
can turn into stone. Then
the remains are called
fossils.
The cliffs of the Grand Canyon,
in Arizona, show layers of
sedimentary rock.

Fish fossil

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The third rock group is called metamorphic
rock. Metamorphic rock is igneous or
sedimentary rock that has changed over a long
time into a new kind of rock. Limestone is
a sedimentary rock. Limestone becomes marble
when it is heated and pressed for many years.
Marble is a metamorphic rock often
used in building.

Marble

Where Rocks Form

Lava cools to form
igneous rock on the
slopes of volcanoes.

Rock particles are carried
by rivers into the sea,
where they form
sedimentary rock.

Examples of Metamorphic Rock

Slate

When rocks melt, they mix, cool, and harden
to form new igneous rock. When rocks are worn
down, the remains form new sedimentary rocks.
Under the right conditions, both igneous and
sedimentary rocks can become metamorphic rock.

Gneiss

Under pressure, igneous
and sedimentary rock can
form metamorphic rock.

Marble, a metamorphic rock, is often used to make floors.

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More About Minerals
Minerals are the most common solid material on
Earth. Almost everything we use contains minerals.
Scientists can tell minerals apart by looking at
things such as color, streak, hardness, and luster.
Color is the easiest to notice. Some minerals come
in different colors. Spinel, for example, is a mineral
that can be red, lavender, blue, green, brown,
or black. The most common variety of
spinel is a clear red.

Streak is the color of the mineral in its
powder form. You can find a mineral’s streak
by rubbing the mineral across a hard surface.
The color of a mineral’s streak is always the
same. This is true even if the mineral itself
comes in different colors.
Pyrite is a mineral. It is called “fool’s gold”
because it is often confused with gold. Pyrite’s
streak is black. Real gold has a yellow streak.

The minerals
quartz and spinel
cling to this rock.
Quartz

Molybdenite streak
Red spinel

Molybdenite

Spinel

Gold

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Pyrite

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Diamond

Platinum

Hardness is how easily
a mineral can be scratched.
Hardness is measured on
a scale of one to ten. One
is the softest and ten is the
hardest. The hardest mineral
is diamond. It cannot be
scratched by anything
but another diamond.
Luster describes how
a mineral reflects light.
Gold, platinum, and silver

are all minerals with a
metal-like luster. The most
common luster is glassy.
Amethyst has a glassy luster.

Amethyst

Minerals in Our Lives
We depend on minerals. When you turn
on a lamp, you are using copper, quartz, and
wolframite. The copper is in the electrical wiring.
Quartz is found in the glass of the lamp’s bulb.
Wolframite is in the metal wire of the bulb.
Anything made of glass has quartz in it.
You will find quartz in drinking glasses, TVs,
radios, and clocks. Quartz is one of the most
common minerals on Earth.

Quartz
The wires inside a
light bulb are made with
wolframite. The bulb’s
glass contains quartz.
Wolframite

Electrical wires are
made of copper.

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Copper

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To stay healthy, your body needs minerals
every day! When you sprinkle salt on food,
you are using the mineral halite. The iron in
meat helps your red blood cells. Chromium
is a mineral that may help prevent a disease
called diabetes.
Calcium and magnesium are important
minerals for your body. Calcium builds bones
and teeth. Magnesium helps muscles tighten
and relax.

Salt

From Rocks to Soil
Soil is the thin layer of loose material that
covers most of the land on Earth. Plants, animals,
and people all depend on soil.
Soil is made up of water, air, bits of rock, and
nutrients. Nutrients are materials that plants need
to help them grow. Some nutrients are the remains
of living plants and animals that have broken down
through a process called decay. Other nutrients
come from the minerals in the soil.

Halite, or salt

Rabbits depend on soil
for food and shelter.

Toothpaste contains
calcium carbonate.
Calcium carbonate, or chalk

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Kinds of Soil
Soil forms in layers. The top
layer is called topsoil. It contains
many nutrients. Below the
Humus
topsoil is subsoil, where
tree roots find their water.
The deepest layer is bedrock.
Topsoil
As bedrock gets broken
down, it becomes soil.
Humus is found in soil.
Subsoil
It is made of decaying
plants and animals.
Clay is made of small
particles. Clay soil is thick,
dense, and traps water.

Sand particles are large and
have a lot of space between
them. Water passes through
Poor soil
sand. Silt has medium-sized with rock
fragments
particles. It lets the right
amount of water in and out.

Loam

Loam is a kind of soil
made of sand, silt, and clay.
Crops usually grow best in
loam because it has the right
amount of sand, silt, and clay.
Rocks, minerals, and soil
are everywhere. Without rocks,
minerals, and soil, we wouldn’t
be able to live. So be sure to
treat the earth beneath you well!

Bedrock

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Vocabulary

Glossary
decay
decay
igneous rock the process of breaking down
the remains of living matter
loam
metamorphic into
rocknutrients
igneous
mineralrock rock that forms when hot,
melted minerals in the center
nutrient
of Earth cool down
rock
sedimentary rock
loam
a kind of soil that plants grow
very well in and that contains sand,
soil
silt, and clay

What did you learn?
1. Which kind of rock forms in layers?
2. What are three ways that minerals
are described?
3. What are some ways minerals help
you to stay healthy?
4.

On page six, you
read about metamorphic rock. Write
to explain how metamorphic rock
forms from limestone, based on
what you have read.

5.

Compare and Contrast How
does soil with a lot of clay compare
to soil with a lot of sand?

metamorphic rock that forms when igneous
rock
or sedimentary rock is changed
by heat or pressure
mineral
nutrient

a solid substance made naturally
from nonliving matter
material that plants and animals
need to live and grow

Picture Credits
Every effort has been made to secure permission and provide appropriate credit for photographic material.
The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

rock

solid matter made of minerals that
are found in and on Earth
Scott Foresman/Dorling Kindersley would also like to thank: 2 (CR), 8 (CR, BC), 9 (CL, BR),
Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).
Opener: Getty Images; 2 Getty Images; Backgrounds: Getty Images.

12 (CR) Natural History Museum, London/DK Images.

sedimentary
rock

rock that forms when layers of
broken rock are pressed together

Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.

soil

the thin layer of loose material that
covers most of the land on Earth
Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America.
ISBN: 0-328-13827-4

This publication is protected by Copyright, and permission should be obtained from the publisher prior to any
prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,
mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to
Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.
3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

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