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wind, rain, overgraizing, forest harvesting, excess sediment, climate, slope, rocks, glaciers, construction

Ice Wedging

a type of mechanical weathering.

Chemical Weathering

occurs when the mineral compostion of the rock is changed.


occurs when a metal is exposed to oxygen and water.

Composition of soil

is made up of rock and mineral fragments, organic matter, air and water.

Where does most organic matter in soil come from?

Plants (leaves, stems and roots, animals that died contribute too)

What causes the organic matter to decay?

Fungi and Bacteria cause decay.

What does the decayed organic material turn into?


What does Humus provide?

It's a source of nutrients for plants.

What mixes the soil with the fragments of rocks?

worms, insects and rodents

What does Humus do for soil?


Soil Profile

a) most plant roots are at the TOP layer of the soil.
b) the top layer is typically DARKER.
c) there are different layers called HORIZONS.
d) The HORIZONS form a soil profile.

How many HOIRIZONS are there and what are they?

There are 4 horizons. A, B, C & D.

Horizon A

Top Soil

Horizon B

Sub Soil

Horizon C

Rock Fragments

Horizon D


Horizon A Top Soil consists of what?

humus, fewer rock and mineral particles, generally dark and fertile.

Horizon B Sub Soil consists of what?

lighter color, less humus, less fertile, contains material that moved down from top soil called leaching. (ex: water - seeps down - humus + carbon dioxide = acid.

Horizon C Rock Fragments consists of what?

partially fragmented rock, thickest soil, less organic material, less leaching.

Which horizon is called the parent material of the soil?

Horizon C

What are Glacial Deposits?

a mixture of Clay, Silt, Sand, and Boulders. (CSSB). Many places on earth and covered by a thick layer of sediment that was deposited by glaciers. Extremely fertile soil

Soil Types

some soils are thick and red, brown with hard rock modules, and some have thick black A horizons.

What causes different types of soil?

Climate ex: deserts, praires and temperate forests.

Dessert soil

little organic material and dryer (less water)

Prairie soil

lots of organic material, thicker/darker soil (A horizon), lots of grass contributes to it.

Terperate Forest soil

thinner A horizon than praire, tree roots and leaves deliver less organic material to deeper parts of soil

What additional factors affect soil type?

rock type - affects vegetation and time affects soil formation -.

What affects a soil profile?


What is Soil Development?

climate, regions, time and slope.

Why is soil erosion harmful?

because plants do not grow as well when topsoil has been removed.

How does soil erosion occur?

WATER & WIND. flowing water carries away sediment that used to be on the field/land.

What is Forest Harvesting?

removing trees for lumber. ex: Tropical Rainforest.

What are some negative affects to Forest Harvesting?

removal of trees leaves soil exposed to weather increasing the damage to soil.


animals eating the vegetation results in slower plant growth, soil exposed to rain and wind and the result is erosion.

How do people contribute to soil erosion?

forest harvesting, overgraizing, and construction.

How des Excess Sediment contribute to erosion?

the build up of sediment clogs rivers, muddies the water, which can harm fish and other organisms.

How to PREVENT soil erosion?

plant trees to protect from wind, replace top soil, manage crops, no-till farming, contour farmng and terrace farming, spray water on soil so wind does not remove top layer,

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