Transcript soil-HorizonLayers

Objective:
Explain what soil consists of
Describe the horizons of soil
Essential Question: Why do soil
horizons form the way they do?
Earth’s Surface Text 4.2
How does soil form?
It takes a long time for soil
to form. Soil forms as rock
is broken down by
weathering and mixes
with other materials on
the surface. Soil is
constantly being formed
every time bedrock is
exposed. Over time, soil
develops layers. We call
these layers horizons.
Horizon 0
Horizons A
B
C
R
Bedrock
Horizon 0
• Thin surface
• Made of organic material
(dead leaves, plants, &
grass)
Horizon A
• Horizon A is made up of topsoil. Topsoil is a
crumbly, dark brown soil that is a mixture of
humus, clay, organic matter, and other
minerals.
Horizon B
The B horizon is
called subsoil.
Subsoil consists of
clay and other
particles that have
washed down from
horizon A. Usually a
brownish-red color.
Horizon C
The first soil horizon
to form from the
weathering of bedrock
is the C horizon.
The C horizon contains
only partly weathered
rocks. Rock is usually a
light yellowish brown
color.
Below the C horizon is where
you will find bedrock.
Bedrock
• Deepest layer, soil and unweathered rock.
Grayish-light brown color
Soil Horizons
Foldable—
1)Color your
“Horizon”
2) Cut to make
flip book and
GLUE in ISN
3) Write the
definition for
each horizon
using this
PPT and your
textbook.
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