A lesson on the formation and composition of natural soil

By: Mrs. Poole

Table of Contents

• What is soil?• How is soil formed?• What’s soil made of? (1)• What’s soil made of? (2)• Bar Graph• Table (Soil Composition)

– Weathered rocks– Organic matter

• Soil profile– 4 layers of soil (O)– 4 layers of soil (A)– 4 layers of soil (B)– 4 layers of soil (C)

• Types of soil• Did you know… (1)• Did you know… (2)• Soil Movie

What is soil?

• Soil is the product formed when rocks break down and mix with water, air, and rotting organic matter.

• Soil holds plant roots.

How is soil formed?

Soil is formed 3 different ways:1. Rocks break down or weather2. Earth carries materials by

water, wind, and ice and drops materials in places where they settle and mix with other materials

3. Living and once-living things turn sand, silt, and rock pieces into a mixture that is food for more life to live and grow.

– The plants attract animals, and when the animals die, their bodies decay.

– Decaying matter makes the soil thick and rich. (YUM!)

What’s soil made of?

5 main ingredients of soil:

1. Minerals – weathered rock such as sand, silt, clay, pebbles

2. Air

3. Water

4. Organic matter (old leaves, dead plants and animals)

5. Living Organisms (tiny living things)

What’s soil made of?

Soil Composition

30%

20%

1%2%

48%

Water

Air

Living Organisms

Organic

Mineral

MineralsWater

Air

Organic Matter

Living Organisms

Bar Graph

Soil Composition

0

10

20

30

40

50

60

Minerals Air Organic Matter LivingOrganisms

Water

Soil Composition

Ingredient of Soil Picture

Mineral

Air

Water

Organic Matter

Living Organisms

Weathered rocks

The weathering of rocks makes soil.

Organic matter decomposes and provides food for living organisms who eat and turn the food into soil.

Soil profile

• Soil changes as you dig deeper and deeper in the ground.

• You can see changes in colors and textures.

• Most soil has 4 layers:– Organic layer– Upper soil layer– Middle soil layer– Lowest layer

4 layers of soil:

O = Organic Layer

– 0-2 inches deep– Takes 100-600

years to form– Living things live

here– Millions of dead

plant and animal organisms are decomposing here

Organic

4 layers of soil:

A = Upper Soil Layer– 2-10 inches deep

– Many plant roots found here

– Dark soil because many chemical reactions as plants & animals grow and die

– Lots of bacteria which helps chemical reactions.

Upper Soil Layer

4 layers of soil:

B = Middle Soil Layer

– 11-30 inches deep– Less living things,

less air, less darker topsoil

– Plants don’t grow well here

– Can find human artifacts like arrowheads or pottery here

Middle Soil Layer

4 layers of soil:

C = Lowest Layer– 31-48 inches deep

– Soil color is orangish/yellowish

– More sandy or more gray clay

– Many pebbles and rocks

– Least amount of living/dead things

– Could still have lot of water

Lowest Layer

Organization chart

Found near coastal regions and deserts.

Course or gritty feeling.

Found where water interacts with soil.

Smooth or slippery feeling.

Found all over the world.

Sticky and rich in clay.

Did you know…

• Soil makes up the outermost layer of out planet.

• There are over 70,000 kinds of soil.

• The color of soil depends on how much chemical reactions are taking place in the soil.

• What kind of soil do we have in Cobb County?

Did you know…

1 Asian elephant = 5 tonsClick on black rectangle

5 tons of topsoil spread over 1 acre would only be as thin as a dime!

Soil Movie

Click on the picture to watch

a movie

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