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Minerals, Rocks,
and Soil
A Science A–Z Earth Series
Word Count: 1,000
Minerals,
Rocks,
and Soil
Written by Rachel Kamb
Visit www.sciencea-z.com
www.sciencea-z.com
Minerals, Rocks,
and Soil
Key elements Used in This Book
The Big Idea: Earth is made up of various living and nonliving materials.
Elements form minerals, and minerals form rocks. Each mineral and
rock can be classified in many ways. Igneous, sedimentary, and
metamorphic rocks form differently and can transform through the rock
cycle. Through weathering and erosion, rocks change, break, and
move. Minerals mix with organic material, forming the soil on which
plants and animals rely. People use nonliving materials as resources by
mining, drilling, and refining them. While seemingly abundant, Earth’s
resources are limited and must be preserved for future generations.
Key words: bedrock, crystal, deposit, drill, element, energy resources, erosion,
fossil, humus, igneous rock, inorganic, lava, magma, matter, metal, metamorphic
rock, mine, mineral, ore, organic, process, raw material, refine, resources, rock,
rock cycle, sedimentary rock, soil, subsoil, topsoil, weathering
Key comprehension skill: Main idea and details
Other suitable comprehension skills: Compare and contrast; classify information;
cause and effect; identify facts; elements of a genre; interpret graphs, charts,
and diagrams; using a glossary and boldfaced terms; using a table of contents
and headings
Key reading strategy: Connect to prior knowledge
Other suitable reading strategies: Ask and answer questions; summarize;
visualize; retell
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Written by Rachel Kamb
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Illustration Credits: Pages 5 (bottom), 20 (bottom): Casey Jones/© Learning A–Z
Minerals, Rocks, and Soil
© Learning A–Z
Written by Rachel Kamb
All rights reserved.
www.sciencea-z.com
Introduction
Earth has everything you need to
Table of Contents
stay alive. It has water, air, plants,
Introduction....................................... 4
Elements and Minerals..................... 5
Rocks................................................... 7
Rock Groups...................................... 9
Igneous Rocks.................................. 9
Sedimentary Rocks......................... 11
Metamorphic Rocks....................... 13
The Rock Cycle................................ 14
and animals. Earth also has land!
Land is where you walk and play.
Your home sits on land, too. What is
land made of? Why is it important?
In this book, you will learn about
nonliving Earth materials that make
up the land.
Weathering and Erosion................. 15
Nonliving materials
What Is Soil?.................................... 17
come in many
Kinds of Soil..................................... 18
colors and shapes.
Layers of Soil.................................... 19
They come in
Using Earth’s Resources................. 21
many sizes, too.
Conclusion....................................... 22
Glossary............................................ 23
Index................................................. 24
3
They can change
Houses sit on land.
4
in many ways.
Elements and Minerals
elements → minerals → rocks
A mineral is made of
Let’s start with elements. They
elements. Minerals
make up everything on Earth.
are solid and inorganic.
They are very,
They were never alive.
very small.
silver
Some minerals have just one element.
elements → minerals → rocks
For example, silver is just made
of silver. Iron is only made of iron.
Other minerals, such as quartz,
Periodic table of
the elements
have two or more elements. Earth
has about 4,000 kinds of minerals.
Sr
Cs
Each mineral has
Cesium
Ds
Rg
Cn
Fl
Lv
Darmstadtium
Roentgenium
Copernicium
Flerovium
Livermorium
its own mix
of elements.
This table lists all the known elements on Earth. Each box
has a symbol for the element and more information about it.
Elements are not the smallest
parts of matter. The tiniest bits
of each element are called atoms.
quartz
5
6
Rocks
Look at the chart. It shows you
many ways to compare rocks.
A rock is made of minerals. It is
How to Describe and Compare Rocks
hard, solid, and natural. A rock can
have many colors and patterns.
Mineral
composition
Rocks have a special mix of minerals.
Size
Rocks can be huge boulders or small
pebbles. They can be as big as a
mountain or as tiny as a speck of dust.
The bits and pieces of minerals
give a rock its colors and patterns.
elements → minerals → rocks
Each rock has a mixture
of minerals in it.
7
8
Shape
Rocks can be flat, round, square,
or almost any other shape.
Color
Rocks come in every color you can
imagine. Many rocks have more than
one color. It depends on the colors
of their minerals.
Texture
Some rocks are rough, while others are
smooth. They can have tiny grains or
large, smooth chunks. Some have long
crystals. Others are full of airholes.
Hardness
The Mohs Scale of Hardness compares
how hard each mineral is within a
rock. Talc is rated a 1 (very soft), and
diamonds are rated a 10 (very hard).
Patterns
Rocks may have streaks, waves, or
lines. They may have dots or be built
layer upon layer. Some rocks do not
have a clear pattern.
Location
An important way to describe a rock
is by where you find it. A beach may
have different rocks than a forest,
desert, or volcano.
Rock Groups
Sometimes lava
cools fast on
Earth has three rock groups. Each
Earth’s surface.
rock group forms in a different
The cooled rocks
way. Let’s learn about each group.
might become
Igneous Rocks
pumice. These rocks
Hot, soft rock called magma lies
are full of tiny airholes.
underground. When magma blasts
Pumice is so light
that it floats in water!
Sometimes magma stays
out of a volcano, it is called lava.
underground and cools slowly.
As magma and lava cool, they
turn into igneous rocks (IG-nee-us).
This cooled rock might become
granite. It is hard and solid.
VOLCANO
igneous rocks
Think of igneous
rocks as fire rocks.
They come from
super-hot rocks.
lava
Obsidian forms
when magma
cools very
quickly. It looks
like black glass.
Granite is used in kitchens
and to build some walls.
magma
9
10
Sedimentary Rocks
Look for fossils in
Some rocks
sedimentary rocks.
are made
Millions of years
from tiny
ago, dead plants
bits of
and animals settled
minerals
Breccia is a type of sedimentary rock.
Fossil of a leaf
to the bottom of seas, lakes, or
called sediment. Water and wind
rivers. Layers of sediment buried
can move the very small pieces.
the plants and
Then the bits settle to Earth in
animals. Then
layers. New layers form on top
rock formed.
of old layers. Weight and pressure
Fossil of a dinosaur footprint
make the layers press together.
Coal is a
sedimentary rock
made of dead
plants pressed
together. Over
millions of years,
under great
pressure, the
plants turned
into rock.
Over a long time,
sediments turn into
sedimentary rocks.
Sandstone is a
sedimentary rock.
It is easy to break.
Look at a side view of
sedimentary rock. You are
seeing a slice of history.
11
The plant or animal
stayed in the rock,
or its shape did.
Fossils help you
learn about the
plants and animals
that once lived there.
12
The Rock Cycle
The word metamorphic comes from
a Greek word that means “to change.”
Why are some rocks called metamorphic?
Rocks go through a rock cycle. They
move up to Earth’s surface. They break
apart and can get pressed together
Metamorphic Rocks
again. They go underground, where
Heat and pressure deep below
heat and pressure can change them.
Earth’s surface can change older
rocks. They become metamorphic
Look at the diagram. It shows
rocks (met-uh-MOR-fick). A weak
how rocks can change from one
rock might turn into a strong rock.
kind to another.
erin
ath
e
w
igneous
rock
g and erosi
on
sedimentary
rock
the rock cycle
metamorphic rock
13
14
he
at
an
dp
ssure
pre
nd
nd
weatherin
ga
ta
er
o
ea
g
ltin
me
Phyllite (top) and gneiss
(bottom) are two kinds
of metamorphic rocks.
on
si
ressure
m e lt i n g
h
Weathering and Erosion
Rocks can change and move.
Weathering changes the size and
shape of rocks. Moving water and
wind often make rocks bang into
An arch caused
by weathering
each other. This makes the rocks
A rockslide
caused by erosion
smooth and round. It can also
Erosion moves rocks. Wind and
break the rocks into pieces.
water can move small pieces of rock
from one place to another. As the
Water can get into the cracks in
rocks move, they bump into other
a rock. In winter, the water may
rocks and move or break them. This
turn to ice. The ice can open the
crack and break the rock into pieces.
Plant roots can
turn into stones, sand, or even dust.
Other things move rocks, too.
grow into a crack,
Glaciers carry rocks downhill in a
too. As they grow,
slow river of ice. Earthquakes or
they can break
the rock open.
causes more erosion. Big rocks can
A tree is splitting a rock. This is
just one example of weathering.
15
heavy rain can make rocks tumble
down mountains.
16
What Is Soil?
Kinds of Soil
Earth’s land is more than nonliving
The world has many
rocks and minerals. Land also has
kinds of soil. Each
organic matter that is alive or once
kind has a different
was alive. Plants, dead animals, and
mix of minerals, bits
animal waste are organic. Soil is a
of rock, and humus.
mix of rocks, minerals, and organic
It can take many
matter. The organic matter in soil is
years for each kind
called humus
of soil to form.
(HYOO-muss).
Soil comes in many
Soil also has air
colors. One soil may
and water. Plants
not feel the same
need soil, and
as another one.
many animals
Soil can be packed
eat plants.
ro
soil
ic mat
te
g an
or
tightly or loosely.
r
nd mine
r
als
c
a
ks
Soil scientists have found
over 10,000 different
kinds of soil in Europe.
17
18
Layers of Soil
Soil changes and moves near the
surface. It changes less underground.
sand
silt
clay
loam
As a result, soil often has layers.
Texture is how something feels.
The thin layer on top is topsoil. It is
It is one way to describe soil.
often soft. It usually has more air
Sand feels gritty because of its hard
and water than deeper soil.
bits of rock. Silt feels like flour. It is
Subsoil is the middle layer. It is
made of bits that are smaller than
drier and harder
sand. Clay feels sticky. It is made of
than topsoil.
Cutaway View
of Soil Layers
even smaller bits mixed with water.
It has more rocks.
Bedrock is often
far underground.
Little air or water
topsoil
Science
In Your The United States has lost a lot of
World topsoil. This is because of farming,
logging, and grazing. With fewer plants, wind
and water cause more soil erosion.
subsoil
topSoil Loss
per year in the
United States
reaches bedrock.
It is often very
Low
Moderate
High
Very High
bedrock
hard and dry.
19
20
Using Earth’s Resources
Conclusion
When we use rocks, minerals, and
Elements make up minerals. Minerals
soil, they are called resources. Some
make up rocks. Rocks can be igneous,
resources are deep below Earth’s
sedimentary, or metamorphic. Rocks
surface. People mine, dig, drill,
can change from one kind to another
or blast the land to get to them.
in the rock cycle.
Many metals we use are found
Weathering and
inside rocks. People use machines
erosion change and
to get out the important metals.
move rocks. Rocks
Other Earth resources can be used
mix with organic
for energy. They help move cars
matter to make soil.
and heat homes.
People need Earth’s resources. We
make and build things with rocks
and minerals. We
grow food in soil.
So we need to use
Mining for metals
resources wisely.
Drilling for oil
21
22
Glossary
elementspure substances; the building
blocks of everything on
Earth (p. 5)
erosionthe process of transporting
and wearing away rocks
or soil as loose particles
are moved by water, wind,
ice, or gravity (p. 16)
fossilsthe remains of plants or
animals that turned to
stone over a long period
of time (p. 12)
igneous
rocks formed by the cooling
rocks and hardening of hot magma
or lava (p. 9)
metalsmaterials, usually hard and
shiny, that allow electricity
and heat to move through
them (p. 21)
metamorphic rocks formed when any type
rocks of rock goes through changes
caused by extreme heat and
pressure (p. 13)
minerala solid, natural material that
does not come from a living
thing (p. 6)
23
resourcessupplies of things that are
valuable or very useful to
people (p. 21)
rocka hard, solid material that
is made of minerals and
is found in nature (p. 7)
rock cyclethe series of changes that
rock undergoes as it shifts
between different types
(p. 14)
sedimentary rocks formed when sediment
rocks is pressed together over time
(p. 11)
soilthe top layer of the ground,
in which plants grow; dirt
(p. 17)
weatheringthe process of wearing
away or otherwise changing
Earth’s surface, caused by
natural forces (p. 15)
Index
atoms, 5
coal, 12
humus, 17, 18
lava, 9, 10
magma, 9, 10
24
Periodic Table of
the Elements, 5
sediment, 11, 12
soil layers, 19