Download 7.5 NOTES How do soils form? Objective: Describe differences in

7.5 NOTES
How do soils form?
Objective: Describe differences in soils in terms of texture, mineral
content, and where the soil was formed
Soil is defined by its texture, or size of its particles. The textures range
from coarse to fine. Sandy soils have a coarse texture, and the largest
particles. Some soils contain silt. Silt particles are smaller than sand
particles, and have a finer texture. The smallest and finest particles in
soil are clay. They also have the finest texture. Adding water to clay
soil makes it feel sticky or muddy.
TRANSPORTED AND RESIDUAL SOIL
Transported soil is soil that has been carried away from the place where
it was formed by running water, glaciers, wind, or waves. Transported
soil may differ from the bedrock, or parent material, beneath it.
Residual soil is soil that has not been carried away. It stays on top of
the bedrock from which it was formed, and has the same chemical
makeup as its parent material beneath.
MINERALS IN SOIL
Weathering rates depend on the mineral makeup of the soil. The kinds
and amounts of minerals depend on the parent material. Different
rocks produce different kinds of soil.
Chemical weathering also affects the minerals in soil. Plants and water
can remove minerals. The removing or washing away of minerals by
water is called leaching. The minerals in the soils are dissolved or
washed away completely. Farmers need to add fertilizers to the soil to
replace minerals used up by plants or leaching.
CLIMATE
An area’s climate also helps to determine the type of soil formed from
bedrock. Temperature and amount of rainfall affect the composition
and texture of soils