Science
Earth’s Surface
Chapter 4 Section 2
Name: __________________________
Date: __________________________
SOIL COMPOSITION
___________________ is a mixture of four materials: ___________________ _____________ particles, organic matter,
_______________ and _____________.
___________________________ rock particles are the main ingredient of ______________.
Water and ___________ make up about _______ to _________ percent of a soil’s volume.
Organic matter makes up about _______ percent
Organic matter in soil comes from the _______________ and ______________ product of __________________,
_______________________ and other living organisms.
The decayed organic matter in _____________ is called ___________________.
All soils are not the same
Different soils are made up of different ingredients and different amounts of each ingredient
The kind of soil that forms in an area depends on a numerous factors:
1. __________________________
2. ______________________________
3. _______________________
4. __________________________
5. ______________________________
6. _______________________
The composition of a ______________ determines what you can __________ in it, what you can ______________ on it,
and what happens when ________________________ falls on it.
SOIL HORIZONS
As you dig a deep hole in the ground, you will notice that the ___________________ soil looks different.
The deeper you go, you will find ___________________ rock particles that are less ____________________________.
There is also less ___________________ matter in ____________________ soil
A ___________ ______________________ is a layer of ______________ with properties that _____________ from
those of the layer __________________ or __________________ it.
There are three main layers of soil: A Horizon, B Horizon, C Horizon
The _______ horizon is the _______________ layer of soil and is commonly called __________________.
It contains the most ____________________ matter of the three layers
Because of the __________________ it is often _______________ in color.
The _____ horizon lies just below the A horizon.
It has little _____________________ matter and usually __________________ or __________________ in color
It contains ___________ and other materials that have washed down from the A horizon
The ______ horizon is the deepest layer of soil.
It contains the __________________ and least _______________________ rock particles.
Its color is typically light ____________________ brown.
The soil horizons in a specific _____________________ make up what geologists call a soil profile.
Different locations can have very different soil profiles.
Ex. –
The A horizons can be very thick in some places and thin in others.
In some areas, one or more horizons might be missing from the profile.
CLIMATE AND LANDFORMS AFFECT SOIL
____________________ kinds of soil______________ in different climates
____________________ also influences the characteristics and _____________________ of the soil that develops from
weathered rock.
Tropical, ____________________, temperate, and _________________ soils are four types of soil that form in different
climate regions.
The _______________ of the land also affects the _______________________ of soil
Mountains soils are very different from ____________ in nearby ____________________.
THE ACTIVITIES OF ORGANISMS AFFECT SOIL
The living ____________________ in a soil have a huge impact on the soil’s __________________________.
Without them, ____________ would not be able to ______________ the wide variety of _____________ the people
depend on to live.
There are three main types of organisms that affect the characteristics of soil:
1) Plants
2) _______________________________
3) Animals
_____________________ such as trees and ___________________ provide most of the __________________ matter
that breaks down to form humus.
Ex. – Trees add organic matter in soil when they lose their branches and leaves
________________________________ include decomposers such as _____________________ and ________________
A ____________________ of soil may contain more than ____________________ microorganisms
Microorganisms decompose dead ______________ and ______________________ and produce nutrients that
__________________ need to grow.
The cycling of ________________________ through the soil and through the plants is a ____________________ process
______________________ such as earthworms, ________termites, mice, ________________, moles and prairie dogs all
make their home in the soil
All of these animals ___________________ and __________ the soil as they ___________________ through it
They create ___________________ in the soil, adding to its _______ content and improving its ability to _____________
and drain water.
______________________ animals also bring partly ______________________ rock to the surface.
Animals return ____________________ to the soil when their bodies _____________________ after death.
PROPERTIES OF SOIL CAN BE OBSERVED AND MEASURED
Observations and ____________ of soil samples reveal what ___________________ the soils contain and what kind of
_______________ will grow best in them.
Farmers use this information to __________________ the growth of _____________ and other plants.
Scientists study many properties including texture, ____________, pore space, ______________________.
TEXTURE
The ___________________ of a soil is determined by the ____________ of the weathered rock particles it contains
Scientists classify the rock particles in soils into three categories: sand, ___________, clay
____________ particles are the _________________ and can be seen without a microscope
Silt particles are smaller than sand particles and need a microscope to be seen.
____________ particles are the _________________.
Most soils contain a mixture of ______________, _______________ and ______________.
COLOR
The color of soil is a clue to its other _____________________.
Soil colors include red, _______________, yellow, green, ________________ and even ______________.
Most soil color comes from iron compounds and humus
_____________ gives soils a __________________ color
Soils with a high ______________ content are usually black or brown.
Bright colored soils will ________________ well.
PORE SPACE
_____________ space refers to the spaces between soil particles
______________ and ______ move through the pore spaces in soil
_______________ roots need both ___________ and ________ to grow
Soils range from about _______ to _______ percent pore space.
An ideal soil for growing plants has _______ percent of its volume as ________ space, with half of its pore space
occupied by ________ and half by __________.
CHEMISTRY
_______________ absorb ___________________ they need from the water in soil
These ______________________ may come from the ______________________ or organic matter in the soil
The nutrients must be dissolved in water in order for plant roots to use them
Farmers may apply _____________ to make soil less acidic.