Dirt on SoilDirt on Soil

What is Soil?What is Soil? SoilSoil forms as forms as

rockrock is is weathered and weathered and mixesmixes with other with other materials on the materials on the surface.surface.

What is soil made out of?What is soil made out of? Soil composition:Soil composition:

A mixture of rock particles, minerals, A mixture of rock particles, minerals, decayed decayed organicorganic material, air, and water. material, air, and water.

HumusHumus is a dark-colored substance that is a dark-colored substance that forms as plant and animal remains forms as plant and animal remains decay.decay.

Humus is Humus is richrich in nutrients that plants need in nutrients that plants need to growto grow

Soil ParticlesSoil Particles

From From largestlargest to smallest particle size: to smallest particle size: GravelGravel SandSand SiltSilt ClayClay

Soil TexturesSoil Textures PermeablePermeable means the ability for materials means the ability for materials

to let to let waterwater pass through them easily. pass through them easily. Clay is less permeable than gravel.Clay is less permeable than gravel. If the texture is too dense (it is not If the texture is too dense (it is not

permeable) and plants will not survive.permeable) and plants will not survive. If texture is not dense enough, plants If texture is not dense enough, plants

may not survive either.may not survive either. LoamLoam is made up of is made up of equalequal parts of clay, parts of clay,

sand, and silt and it is the sand, and silt and it is the bestbest for for growing plantsgrowing plants..

HorizonsHorizons A soil horizon is a layer of soil that A soil horizon is a layer of soil that

differs in color and differs in color and texturetexture from the from the layers above or below it.layers above or below it. A Horizon (topsoil)A Horizon (topsoil) B Horizon (subsoil)B Horizon (subsoil) C Horizon C Horizon BedrockBedrock

A Horizon A Horizon TopsoilTopsoil: a crumbly, dark brown soil : a crumbly, dark brown soil

that is a mixture of humus, that is a mixture of humus, clayclay, and , and other minerals.other minerals.

This is what you walk on outside…This is what you walk on outside…

B Horizon B Horizon Subsoil: Subsoil: usually consists of clay usually consists of clay

and other particles washed down and other particles washed down from the from the AA horizon, but contains horizon, but contains little humus.little humus.

Below the topsoil, the Below the topsoil, the subsoil is a little lighter in subsoil is a little lighter in color color than the topsoil.color color than the topsoil.

C Horizon C Horizon Contains Contains partlypartly weathered rock weathered rock

This is where you will see bigger rocks This is where you will see bigger rocks and less soil.and less soil.

BedrockBedrock BedrockBedrock is the is the solidsolid

layer of rock beneath layer of rock beneath the soil.the soil.

Once the bedrock Once the bedrock breaks down towards breaks down towards the top, it continues the top, it continues to weather and turns to weather and turns into into topsoil.topsoil.

How fast is soil made?How fast is soil made?Soil develops the Soil develops the quickesquickest in areas with a warm t in areas with a warm and rainy climate (temperature/climate).and rainy climate (temperature/climate).

Areas with Areas with limestonelimestone weather quicker than weather quicker than areas with granite, so for rocks weathering areas with granite, so for rocks weathering occurs based on the type of rock and occurs based on the type of rock and climate.climate.

What else is down there?What else is down there?Plants contribute the most to Plants contribute the most to humushumus, which is , which is in the topsoil.in the topsoil.DecomposersDecomposers are the organisms that break the are the organisms that break the remains of dead organisms into remains of dead organisms into smallersmaller pieces pieces and eat them with chemicals.and eat them with chemicals.

Fungi (mushrooms and mold)Fungi (mushrooms and mold) BacteriaBacteria EarthwormsEarthworms

Review QuestionsReview Questions

1.1. What is What is soilsoil??

2.2. Explain how Explain how humushumus is helpful for soil? is helpful for soil?

3.3. What are the differentWhat are the different soil horizons soil horizons??

4.4. Put these in order from Put these in order from top to bottomtop to bottom::

Subsoil Bedrock TopsoilSubsoil Bedrock Topsoil

Chemical vs. MechanicalChemical vs. MechanicalList the agents and/or processes of chemical and mechanical weathering: List the agents and/or processes of chemical and mechanical weathering:

water, oxygen, animals, acid rain, pressure, water, oxygen, animals, acid rain, pressure, freezing/thawing(ice), oxidation, living freezing/thawing(ice), oxidation, living organisms (lichen), plant growth, abrasion, organisms (lichen), plant growth, abrasion, carbon dioxide, ice wedgingcarbon dioxide, ice wedging

Chemical Mechanical

IX. W.E.R.D.S 38-IX. W.E.R.D.S 38-

pg. 39 Weatheringpg. 39 Weathering

EQ: What is weathering?EQ: What is weathering?

Vocabulary cut-out MatchingVocabulary cut-out Matching