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The Scoop on Dirt
Soil
• Soil is made up of
weathered rock,
including gravel, sand,
and silt.
• Topsoil comes from
subsoils and rocks
beneath the surface.
• Topsoil takes
thousands of years to
form.
Photo courtesy of USDA NRCS
What is a Natural Resource?
• Something that people can use in order to live.
• Something that is not man-made, but has formed
naturally over hundreds, thousands, or even
millions of years.
• Something that cannot be easily replaced once it is
used up.
Can we say that topsoil is a
valuable natural resource?
• How is it used by people in order to live?
• Can we make it in a “topsoil factory”?
• If we use it up, can we easily get more?
How can we lose topsoil?
• Water can wash it
away with rain and
flooding.
• Wind can blow it
away.
• This process is called
erosion.
Photo courtesy of USDA NRCS
How can we conserve topsoil
and prevent erosion?
• Roots of plants help to
hold the topsoil in place.
• Where can we put plants
so that their roots can hold
the soil?
–
–
–
–
On hillsides.
Along rivers and streams.
Around the edges of fields.
Can you think of a place?
Photo courtesy of USDA NRCS
Soil Types
• Soil is made up of organic and inorganic substances.
Soil Types
• Soil is made up of organic and inorganic substances.
Organic means
substances that were
once living such as
leaves, twigs, remains of
animals, and
microorganisms.
Soil Types
• Soil is made up of organic and inorganic substances.
Inorganic means nonliving substances such as
rocks and gravel.
We can group soil into three
types:
We can group soil into three
types:
• Clay (or clayey soil)
We can group soil into three
types:
• Sand (or sandy soil)
We can group soil into three
types:
• Loam (or loamy soil)
We can group soil into three
types:
• Clay (or clayey soil)
• Sand (or sandy soil)
• Loam (or loamy soil)
Clay
• Clayey soil is made up of
tiny particles that are too
small to separate.
• Clay feels powdery when
dry and sticky and slimey
when wet.
• Clay forms hard clods
when dry and sticky
clumps when wet.
• Because the particles are
so small, water cannot
drain well from clay.
Photo: Martha Rogers
Sand
• Sandy soil is made up
small bits and pieces of
rock and smaller particles
called silt.
• Sand does not stick
together when it is wet or
dry.
• Sand particles are loosely
packed and water drains
through it quickly.
Photo: Martha Rogers
Loam
• Loamy soil is a mixture of
sand, clay, and organic
materials called humus.
• Loam does not become
sticky when wet, nor is it
powdery when dry.
• Because it contains
humus, loam is a rich soil
that holds water and also
drains well.
Photo: Martha Rogers
Let’s do an experiment to see
which soil would be best for
growing plants!
Photo: Martha Rogers