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Earth Science
The Formation of Soil
Parts of the Earth
• The crust of the Earth is an extremely thin,
less-dense solid covering over the mantle—it
essentially floats on top of the mantle
• The mantle makes up the majority of the
Earth, and surrounds a small core of iron.
Parts of the Earth
Structure of the Earth
Parts of the Earth
• The outermost portion of the mantle is
solid.
• The crust and solid outer mantle are
collectively known as the lithosphere.
• The asthenosphere is a thin layer below
the outer mantle capable of plastic flow.
Parts of the Earth
Structure of the Earth
Plate Tectonics
• Plate tectonics is the concept that the outer surface
of the Earth is made of large plates of crust and
outer mantle that are slowly moving over the surface
of the liquid outer mantle.
– Heat from the Earth causes the slow movement.
– Plates are pulling apart in some areas, and
colliding in others due to convection cells.
– These building processes are counteracted by
processes tending to make elevated surfaces
lower—i.e.erosion.
Plate Tectonics
Tectonic plates
Plate Tectonics
• Evidence that plates are moving:
– Earthquakes
– Volcanoes
• both happen at plate boundaries
• The asthenosphere provides the plates
with a surface on which they can move—it
is pliable because it is hot.
Plate Tectonics
• Heat from Earth’s
inner and outer cores
is transferred through
the mantle by a
process called
mantle convection.
– The mantle moves the
plates along with it as
it convects.
Plate Tectonics
Subduction
Destructive
margin
Mid oceanic ridge
Constructive
margin
Convection cells
Plate Tectonics
• A mantle plume is an upwelling of
abnormally hot rock within the Earth's
mantle.
– when they reach shallow depths, they are
thought to be the cause of volcanic centers
known as hotspots.
– Hawaii was formed by mantle plumes.
Plate Tectonics
Mantle plume
Geographic formations
• Where 2 plates are pushing against each other,
mountains form.
• Where 2 plates are pulling away from each
other, cracks in the lithosphere form.
Geographic Formations
• Mountain ranges form where 2 plates come
together.
– Himalayas
– Cascades
– Andes
Diversity
• Diverse geographic formations lead to ecological
diversity.
• Ecological diversity leads to biological diversity
(biodiversity).
– organisms have adapted (evolved) to live in a certain
geographic region.
• Examples:
–
–
–
–
Artic hare
Deep water fish
Mountain goats
Bison
Diversity
• Geographic formations can lead to isolation of
populations.
– Examples:
• Islands
• Mountain ranges
• Bodies of water
– Isolation of populations leads to speciation
• This means that the population can only reproduce with its
own kind.
• Example:
• Eastern Meadowlark vs. Western Meadowlark
• Kiiwii in Hawaii
Geographic Formations
• Think of the effect of
elevation on climate
and vegetation.
Soil Formation
• Although mountains are constantly being
formed by converging plates, erosion is
continually breaking down the mountains.
• Due to this building and breaking down,
soil is formed.
– The type of soil depends on the source and
the amount of weathering it has experienced.