Similar to my other SOIL slide show but pitched more for 3re and 4th grade students

1. SOIL, HOW IT IS FORMED
More elementary
than my other
SOIL slide show
and pitched more
for 3rd or 4th
grade students.
By Moira
By Moira Whitehouse PhD

2. The continents have a
layer of solid rock, the
crust, covering the hot
stuff in the mantle.
The continental crust, then, is mostly covered
with thick layers of soil.

3. Thankfully, soil covers most of the Earth’s solid
crust (bedrock).
Why do we care?
Plant growth, that
allows us to
live, occurs on the
top layer of soil.
layers of Below that layer are
soil several other
layers, some that
D provide minerals and
bedrock
ores for our use.
http://www.nrcs.usda.gov

4. What is soil made of?
Even though
soil looks like
one thing, it is
really made up
of many
different kinds
.
of things.
Two of the main things are: 1. tiny, tiny pieces
of rock and 2. the rotten remains of dead
plants and animals.

5. Soil:
Tiny pieces of rock) Humus—organic matter
(remains of
dead plants and animals)

6. First, looking at that part of the soil that is tiny,
tiny pieces of rock.
Through the process called weathering big
rocks are broken into smaller and smaller
pieces. The smallest pieces are called soil.

7. People can
break rock
into smaller
pieces with a
sledge
hammer.
But people are not the main reason that rocks
are continually being broken up into smaller and
smaller pieces until they become soil.

8. Weathering is caused in nature by such things
as wind, water, and temperature changes that
break the rock into ever smaller pieces.

9. The weathered rock in soil at some point
in time started out as a bigger rock,
maybe a large boulder.
In the process of being weathered, the
size of the particles of rock become
smaller and smaller—boulders to large
rocks, to smaller pieces of rock to
pebbles to soil.

10. Big rocks become smaller
and smaller
and smaller
until they
are soil.

11. Over hundreds, maybe thousands of years,
it could have happened something like this.
Soil
Soil

12. Some rocks break down into smaller
pieces more easily than other rocks.
Those rocks that are more easily worn
away are called soft.
And those that are less easily worn away
are called hard.

13. Activity to show differences in hardness of rock.
•Give the students a small hard rock, a small
piece of soft sandstone rock, a sugar cube and
a piece of chalk. •Ask them to weather the
rocks by rubbing them against one another.
•Tell the students that the chalk and sugar
cube are models of rock.
Ask the students if some of the “rocks” were
more easily weathered than others. Explain
those rocks are called soft and the ones less
easily worn are called hard.

14. Now let us discuss, some of the things in
nature that cause rocks to break into
smaller and smaller pieces.
In other words, what are some of the
things that cause rocks to weather.

15. One of these things is moving water.
Running water in rivers and streams carry
rocks downstream causing them to hit one
another and break apart.

16. Water
running over
large rocks
causing them
to break into
smaller rocks.

17. Imagine rocks tumbling along the bottom.
As the sand and gravel
carried by the water rub
against the rocks in the
river, they become
smooth and rounded and
are called river rocks.
Notice how smooth
and rounded these
river rocks are.

18. To see an animation of this process, open
http://whs.moodledo.co.uk/mod/resource/view.php?inpopup=true&id=26639
and choose “click direct link to file”. When finished, close the window to the
internet and you will be back on the slide show.

19. When a river flows rapidly over a plateau, it
breaks the rocks into smaller and smaller pieces
of rock. The fast moving water carries these
pieces of rock down the river creating a canyon.
.

20. The following activity may be used to
demonstrate weathering by moving water.
•Place a piece of soft sandstone in a
plastic jar or vial along with a harder rock
and some gravel. •Add some water.
•Have the students shake the container
back and forth. •After several minutes
pour the contents out on a plastic plate
and observe what has happened.
Discuss how this activity models weathering
of rock due to moving water and rocks
banging together.

21. Another thing that weathers rock is blowing
sand. As it rubs against rocks can break them
into smaller and smaller pieces.

22. Blowing
sand rubs
away the
softer rock
changing it
into soil.
The harder
rock is left
behind.

23. Activity to demonstrate weathering by
blowing sand.
•Place a piece of colored chalk and salt in
a plastic jar or vial. •The chalk is a model
for rock and the salt a model for sand.
•Have the students shake the container
and then pour its contents on to a plastic
paper plate and observe.
Discuss the results of this activity and
how it models weathering by blowing
sand.

24. Water gets into cracks in the rock. If this water
freezes and melts and freezes and melts time
and time again it can break the rock apart.

25. To see an animation of frost wedging, open
http://www.phschool.com/webcodes10/index.
cfm?fuseaction=home.gotoWebCode&wcprefi
x=cul&wcsuffix=2052
and play the small video. When
finished, close the window to the
internet and you will be back on
the slide show.

26. Rocks break as water freezes in cracks

27. Activity to demonstrate weathering by
water that expands when freezes
expands and can break open a rock.
•Place a can of liquid coke in the freezer
overnight and observe what happens.
Discuss how this activity models
weathering of rock due to the fact that
water when it freezes expands and can
cause rocks to break.

28. The Grand Canyon was formed by these three
things in nature: moving water in a river, wind
carrying sand, and the repeated melting and
freezing of water in the cracks in the rocks.
Colorado River

30. In review, ...so what is weathered rock?
Pieces of rock that have been broken down
into smaller pieces by the forces of nature—
water, wind, ice, etc. are called weathered
rock.
These pieces of rock may be a huge boulder
or the the size of a grain of soil.
The smallest pieces of weathered rock is
called soil.
Some of these pieces of rock may be small that
we can only see them under a microscope.

31. Now for the other part of soil humus.
Humus is the organic part
of soil—that which was
once living.
How is it formed?
Humus is formed when dead plants
and animals rot or decay.

32. Bacteria are the smallest living
organisms, and the most numerous of the
decomposer (living things that cause
decay).
A teaspoon of fertile soil generally
contains between 100 million and 1 billion
bacteria.
As they eat the dead plants and animals, they
carry out most of the decomposing that
occurs in the soil.

33. http://soils.usda.gov
Magnified bacteria found in the soil.

34. Fungi is the name for simple organisms (living
things) including mushrooms, molds and
yeasts.
Next to bacteria, fungi are the most efficient
decomposers.
Fungi are not plants; they can't make their own food.
They absorb their nutrients from the organisms
they are decomposing. In the process they release
enzymes that cause dead plants and animals to rot
or decompose.

35. http://www.flickr.comBenimoto
http://www.flickr.comFuturilla
Mushrooms growing on logs
http://www.flickr.comscoobygirl

36. Invertebrates
(animals without
backbones) are also
decomposers.
Important
invertebrate
decomposers are:
Pill bugs
http://www.flickr.comzimpdenfis

37. Decomposing
mites
Millipedes

38. Activity to show how leaves and other organic
material can decompose and form rich black soil.
•Place samples of compost on the students’ tables
and ask them to observe. •Be sure to give the
students samples of various degrees of
decomposition. •Explain the bacteria that cause
most decomposition are too small for us to see.
Discuss how dead plants and animals can
decompose and change into blackish colored soil
and how most soil is a mixture of weathered rock
and rotten plants and animals.

39. So in review: What are two parts of soil?
Soil:
Tiny pieces of rock Humus—organic matter
(remains of
dead plants and animals)

40. What is the process in nature called that
causes rocks to break into smaller and
smaller pieces?
Yes, weathering.
What are some forces in nature that
causes the weathering of rocks?

41. And finally, you should remember how
the other part of soil, humus, is formed?
Soil—it is the
dirt we in
science choose
to love.