Download 7.4 NOTES How does soil form? Objective: Explain how soil is a

7.4 NOTES
How does soil form?
Objective: Explain how soil is a product of weathering and organic
processes
FORMATION OF SOILIf you dig a hole through the soil, you will eventually hit a layer of solid
rock called bedrock. Soil is formed when bedrock is broken down by
weathering. Over time, the bedrock, or parent material, is broken
down into smaller pieces until they become soil particles.
LIVING THINGS AND SOILMosses and lichens form
acids that help break
down rock. Bacteria in
the soil help break down
decaying plants and
animals. Fungi such as
mushrooms also help to
break down dead or
decaying organisms. The
decayed remains of plants
and animals are called
humus. Soil rich in humus
is ideal for growing things
in, because it has a lot of
minerals in it.
Organisms living in the
soil help to break it down
through burrowing. Large
pieces are broken apart
letting air and water in.
The water helps to speed up the breakdown of rock.
SOILSand, silt, and clay help make up soil. Pieces of rocks, minerals, and
humus are also in soil. Humus makes the soil a dark color. Air and
water are also in soil.
Soil is important because it supplies plants with water and support.
Important nutrients, such as potassium, phosphorus, and nitrogen are
part of soil. Our homes and food are built on soil as well. Without soil,
few organisms could live on Earth.