Earth Science Rocks!
Warm up October 9
Question:
Why do you think caring & principled might be good
learner profile terms for your new unit on soil?
Earth Science Rocks!
MYP Unit Question: How does land
change?
 Area of Interaction: Environment


Learner Profile: Caring and Principled
Earth Science Rocks!

Standard: Investigate the scientific view
of how the Earth’s surface is formed.

Learning target: Today I am learning
about soil because human survival
depends on it.
Activating strategy
Soil analyzer
Soil Formation

Loose weathered
material on Earth’s
surface where plants
can grow

Soil

How does soil form?  Soil forms as rock is
broken down by
weathering and mixes
with other materials

Bedrock

Solid layer of rock
beneath the soil
What is the composition of soil?
Soil is a mixture of
rock particles,
minerals,
decayed organic
material (humus),
air, and water

Why is humus good?
Makes spaces for air and water
 Rich in nitrogen and minerals that plants
need to grow

Organisms in the soil
Living things make space for air and water in
soil
 Decomposers break down the remains of dead
organisms into smaller pieces and digest them
with chemicals.

What is a soil’s texture
Soil texture depends upon size of individual particles
 Gravel – 2mm or larger
 Sand – less than 2 mm
 Silt - less than 1/16 mm
 Clay – less than 1/256 mm

Clay soils
Dense, heavy texture
 Hold a lot of water
 Not much space for air

Sandy soils
Water drains quickly
 Lots of space for air
 Nutrients wash out of the soil

Loam
Soil with equal parts clay, sand and silt
 Crumbly texture that holds both air and
water

Soil horizon

A layer of soil that differs in color and
texture from the layers above or below it.
Mrs. McIntire
standing by a soil
profile
at
Red Top Mountain.
Soil horizons
A horizon – top soil – crumbly, dark
brown soil that is a mixture of clay,
humus, and other minerals
 B horizon – sub soil – usually clay and
other particles washed down from A
horizon, little humus
 C horizon – partly weathered rock

How do horizons form?
How do the horizons form?
Bedrock weathers and forms C horizon
 A horizon develops from C horizon when
plants add organic material to soil and
rocks mechanically and chemically
weather
 B horizon develops when rainwater
washes clay and minerals from A horizon
into B horizon.
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