Transcript Soils
Soils
Earth’s Changing
Surface
Review
Weathering
– breaks down rock
– Mechanical
– Chemical
Erosion
– removes the rock particles
What is soil?
The
loose, weathered material on
Earth’s surface in which plants can
grow.
Soil
Bedrock
- the solid layers of rock
beneath soil.
Soil Composition
Mixture
of rock particles, minerals,
decayed organic material, water, and
air
Humus – decayed organic material in
soil
Soil
Fertility
of Soil – measures how well
the soil supports plan growth.
– Rich in humus has high fertility
Why
does fertility of soil matter?
Soil Texture
What
does soil feel like?
Sand feels coarse and grainy
Clay feels smooth and silky
Soil
texture depends on the size of
soil particles.
Soil Particle size
Clay
Silt
Sand
Gravel
Less than Less than Less than 2 mm and
1/256 mm 1/16 mm 2 mm
larger
Loam
Soil
that is made up of about equal
parts of clay, sand, and silt is called
loam.
Soil Formation
Forms
as rock is broken down by
weathering and mixes with other
materials on the surface.
Soil Formation
Soil
Horizons
– A layer of soil that differs in color and
texture from the layers above or below
it.
Soil Horizons
A Horizon
Topsoil
– a crumbly, dark brown soil
that is a mixture of humus, clay, and
other minerals.
Develops as plants add organic
material to soil and plants weather
rock.
B Horizon
Subsoil
– clay and other particles
washed down from the A horizon,
but little humus.
Soil Types
Thousands
of different types of soil
in U.S. alone
Classified based on climate, plants,
and soil composition.
Living Organisms in Soil
Some
soil organisms make humus
Some soil organisms mix the soil and
make spaces in it for air and water.