Warm-up for Today

Put your Erosion article summary in the Turn-In Bin.

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Soil Formation and Composition

Section 7-2

Dirt Excrement Filthy or soiling

substance Something

worthless

Synonyms: filth, dust, grime, muck

SoilThe loose

upper layer of the Earth’s crust in which plants can grow

We do NOT say “Dirt”,

We say “SOIL” !!!

Where does soil come from?

Weathered Rock

+ other stuff

Soil

Bedrock The solid rock in

Earth’s crust When exposed at

the surface, it weathers into smaller and smaller pieces to become soil

Bedrock weathers to Rock Particles

What is the “other stuff?”

2. Humus

3. Air

4. Water

Humus The organic

part of soil Formed from

decomposed organisms

dark-colored Rich in

nutrients

Loam Loam is the BEST kind of soil.

Loam has a good balance of air and water, and holds LOTS of nutrients.

Loam contains equal parts of • Sand (drainage)

• Silt

• Clay (holds water)

Soil Horizons

O = litterA = topsoilB = subsoilC = parent

materialbedrock

Life Science RE:visitedThe WeatherersThe DefecatorsThe DecomposedThe DecomposersThe Aerators

Let’s Review!

1. What is the relationship between weathering and soil?

Let’s Review!

2. What different materials make up soil?

Let’s Review!

3. What is the best kind of soil?

Let’s Review!

4. How do plants and animals affect soil?

Bedrock weathers to Rock Particles

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DEPOSITION

depostion

Material added to land

1. Sediment stops moving (erosion)

2. Organic stuff deposited

LoessLoess