Transcript Internal Structure of the Earth

Internal Structure of the
Earth
Plate Tectonics
Sea Floor Spreading
Internal Structure of the Earth
The Earth has four
internal layers:
• Crust
• Mantle
• Outer core
• Inner core
Earth’s Interior
How do we know there are four
layers?
• We don’t, it’s a theory!
• Using earthquake waves, they can tell
whether an object is a liquid or a solid, so
by using that information, they theorized
about the interior layers of the Earth
Seismic waves and the Earth’s
Interior
Layers of the Earth
• Crust
– Made out of ocean crust or continental crust
– Thinnest layer
– The one we live on
– We have never dug through this layer
• Ocean crust: Dark, dense, and thin
• Continental crust: Light, less dense, and
thicker
Ocean Vs. Continental Crust
Basalt = Ocean Crust
Granite = Continental Crust
Mantle
• The mantle is the thickest layer
• The material is similar to Jello—not quite a solid,
but not a liquid either
• The elasticity of the substance allows the plates
to move around the planet
• The mantle is broken into two parts
– Lithosphere: upper mantle and crust
– Asthenosphere: lower mantle
Outer Core/Inner Core
• The outer core is made out of liquid Iron and
Nickel
• The inner core is a solid layer made out of Iron
and Nickel
• Both layers make up the majority of the weight of
the planet
Theory of Continental Drift
• The theory that
continents drifted
across the ocean to
get their current
spots on the globe.
• First suggested by
Alfred Wegner
• First used the idea of
one super giant
continent called
Pangaea.
Evidence?
• What was the evidence behind Wegner’s
idea?
• The continents fit together like puzzle
pieces.
• The fossils and rocks on separate
continents being identical.
• Climate regions (found by looking at
fossils) that did not match up with the
positions the continents are located today.
What made it go?
• Wegner believed that the continents
floated on the waters of the ocean to get to
their current locations.
Theory of Seafloor Spreading
• Molten material rises at
the Mid-Ocean Ridge.
• The material flows away
from the ridge, carrying
the land that was once
together, further apart.
Theory of PLATE TECTONICS
• First accepted in 1968 by a man named
Hess.
• Combined the ideas of seafloor spreading
and continental drift.
• States that the Earth’s crust and upper
mantle are broken into sections called
plates.
Why do the plates move?
• Hot magma from within the Earth rises to
the surface then cools down and sinks
back into the Earth.
What makes the plates move?
1. New seafloor is
created and
spreads out.
2. The continents
on either side
begin to move
away from each
other.
What makes the plates move?
3. Dense seafloor
hits continental
land.
4. Denser floor goes
into the mantle and
melts.
How do the plates move?
• The plates move in
three different
ways:
• Collide
• Separate
• Slide past each
other
Convergent Plates
Continent vs. Ocean
• The more dense ocean
plate slides under the less
dense continental plate –
called Subduction
• Chains of volcanoes are
formed along the edge of
continents. Also trenches
are formed off the coast of
the continent.
• The Cascade Mountain
chain is formed this way.
Convergent Plates
Ocean vs. Ocean
• Both dense plates are
pushed towards the
center of the Earth
• Extremely deep trenches
are formed, and also
chains of volcanic
islands are created
(island arcs)
• The Japanese Islands
are formed this way.
Convergent Plates
Continent vs. Continent
• When two continental plates
hit both plates are forced
up. No subduction occurs.
• Mountains are formed, not
volcanoes.
• The Himalayan Mountains
in India are formed this way.
Transform Boundary
• When one plate slides
past another.
• The most famous is
the San Andreas fault
in California.
• No creation of
anything, just
destruction.
Divergent Boundary
• When two plates
separate from each
other.
• The Mid-Atlantic ridge
is the best example.