Download Ch. 2 - Mr

The Earth Formed
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If scientists have never studied any
materials from a depth below 7 miles,
then how is it that we know what is in
the center of the Earth? How can we
know what the core of the Earth is made
of, if we have never seen it?
How Do We Know?
• The answer is actually quite simple. While it is true
that we can not study the Earth’s core using visible
light, we can study it using other senses. The most
important thing we use to sense the Earth’s core are
seismic waves. Seismic waves are waves of energy
caused either by earthquakes, or by massive
manmade explosions.
• Scientists are able to measure these waves as they pass
through the Earth. As these waves encounter different
materials, they change in important ways, becoming
longer, shorter, faster, or slower. Geologists study these
changes in the waves, and are able to draw conclusions
about what the core of the Earth must look like.
Crust
• The first layer consists
of about 1o miles of
rock and loose
materials, scientists
call the crust.
Underneath the
continents, the crust is
almost three times as
thick, as it is under the
oceans.
Mantle
• Traveling beyond the Earth’s
crust, we next encounter the
mantle. The mantle extends
to a depth of approximately
1,800 miles, and is made of a
thick solid rocky substance
that represents about 85%
of the total weight and mass
of the Earth.
Outer Core
• Traveling still deeper within
the Earth, we next would
encounter the Earth’s outer
core, which extends to a
depth of around 3000 miles
beneath the surface. It is
believed that this outer
core is made up of superheated liquid molten lava.
This lava is believed to be
mostly iron, and nickel.
Inner Core
• Finally, we would reach
the Earth’s inner core.
The inner core extends
another 900 miles inward
towards the center of the
Earth. It is believed that
this inner core is a solid
ball of mostly iron, and
nickel.
Plate Movement
• Continental Drift –
Theory that the
Continents were
once joined and
then slowly drifted
apart
Continental Drift Video
Plate Movement
• Plate Tectonics –
refers to all of
the physical
processes that
create many of
the Earths
physical features
Plate Movement
How are Mountains Created?
• Spreading (Divergent)
– Sea Plates pulling apart
• Results in undersea volcanic mountains, ridges and
some islands
Building Mountains
How are Mountains Created?
Building Mountains
• Subduction (Convergent)
– When heavier plate dives beneath lighter plate
• Continental
Continental
• Continental
Sea Plate
Earthquakes and Volcanoes
Building Mountains
• Faults – When plates grind or slide past each
other, creating cracks in the Earth’s crust.
– When plates slip along fault lines it causes
Earthquakes
– E.g. San Andreas Fault
Earthquakes and Volcanoes
• Volcanoes – Mountains formed by lava or by
magma that breaks through the Earth’s crust.
• Ring of Fire –
Zone of earthquake and
volcanic activity around
perimeter of Pacific Ocean.
Ch. 2 Sec. 3
Earth’s Water
Water Cycle
• 70% of the
Earth is
Water
Bodies of Salt Water
• Oceans – 97% of
Earth’s Water
• Seas, Gulfs and
Bays – Smaller than
Oceans and often
partially enclosed by
land
• Desalination –
Process of turning
ocean water into
freshwater by
removing the salt
Bodies of Freshwater
• 3% of Earth’s total
water supply is
freshwater.
– 2% is frozen in
glaciers and ice caps
– Lakes, streams and
rivers contain less
than 1% of Earth’s
water
Bodies of Freshwater
– 0.5% is found
beneath Earth’s
surface
• Groundwater –
freshwater that lies
beneath the Earth’s
surface
• Aquifer –
Underground porous
rock layer often
saturated by very
slow flows of water