SOIL FORMATION

1. Topography-

the shape of the landscape. That shape is called the topography. When you have a slope and it rains, there will be drainage.

The runoff carries away small rocks and minerals. This runoff winds up in valleys or in the ocean. It slowly builds up and the small pieces make soil.

Soil will be much thicker and fertile at the bottom of a slope than the top

Factors that affect soil formation

There are climatic effects that create soil. Moisture and rain combine with the temperature

to do amazing things to rocks and causes runoff and erosion. Those physical activities break down the rocks and hard surfaces.

Temperature plays a role when you move below and above the freezing point. When water freezes, it expands. Rocks and soil that hold water can be cracked when the water freezes and expands.

2. Climate

What's in the soil is dependent on it’s parent

material. The type of soil under your feet is dependent

on the bedrock deep below the surface. As the bedrock breaks down, smaller pieces

move to the surface and mix with the existing soil

3. Parent Material

Time plays an important part in the process. You need time to make soil. it takes a long time to break down bedrock.

We can't just sit and watch this process happen, it can take millions of years!

4. Time

Soil is also created by biological factors. You'll find that soil is half minerals/rocks and

half air/water. All sorts of biological things are happening in the air/water space. The organic material is most important. There are tiny living organisms (like bacteria) that break down organic stuff. The organic stuff is called humus.

There are also roots and tunneling creatures that work like the microbes. They turn the soil around and move it.

5. Biological

Weathering – breaking down rock at or near

the surface of the earth. It affects the rocks in place and no transport is involved. This distinguishes weathering from erosion

Erosion- breaking down soil by transportation

Weathering

Chemical reactions break down the bonds

holding the rocks together, causing them to fall apart, forming smaller and smaller pieces.

Chemical weathering is much more common in locations where there is a lot of water.

Warmer temperatures are also more friendly to chemical weathering.

Chemical Weathering

Chemical weathering

Mechanical weathering takes place when

rocks are broken down without any change in the chemical nature of the rocks. The rocks are broken down by physical force

The forces that break rocks down can be numerous, and include such things as the Earth’s crust slowly moving. When great amounts of pressure build up, the resulting mechanical effect can be that very large joints, or faults are created.

Physical Weathering

Physical Weathering