Transcript Structure of the Earth

Earth layers, plates
Chapter 11
Inner core: solid
pressure from
above layers.
temp 5500°C
Fe Ni
Outer core: liquid
Fe Ni
temp 5500°C
Mantle: largest layer
Si O Mg Fe
plastic like
acts as a solid
but flows like a liquid
when under pressure
ex. Silly putty or
taffy
Crust: varies in
thickness
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Thick – continental
crust - granite
Thin – oceanic crust
– basalt
Crust is divided into
sublayers
Lithosphere – crust
and upper mantle
- broken
into 12 large plates that
float on the mantle.
Asthenosphere –
plastic like layer below
the lithosphere
Mohorovicic'
discontinuity –
boundary between crust
and mantle.
Lithosphere
Continental Drift
Alfred Wegener –
1912
proposed theory of
continental drift
continents have
moved to their
current locations
Theory of continental
drift
One continent –
Pangaea
200 m years ago
Panthalassa – one
sea
Pangaea separated
into
Laurasia
Gondwanaland
Separated by the
Tethys Sea
Clues that support
Continental Drift
Pieces of continents fit together like a jigsaw
puzzle
Fossil clues – Mesosaurus(lived on land and
in fresh water)
- found in South American and
Africa
Glossopteris – found in Africa, Australia,
India, South America and Antarctic
- various climates
- must have once been joined
Climate clues – fossils of warm plants
found in the arctic
Glacial deposits – grooved marks in
bedrock found in SA, Africa, India, and
Australia
- must have been
covered with glaciers at one time near
south pole
Rock clues – If continents connected
than rocks that make them up should be
the same.
- similar rock structures are
found on different continents
ex; Appalachian Mts similar to
mountains in western Europe and
Greenland
Wegener’s theory was laughed at even
though he had evidence
After his death more evidence of how
the continents were able to move were
discovered to prove Wegener correct.
Mid-Atlantic Ridge
Longest mountain
range on earth
Extends from
Iceland along middle
of Atlantic
Mid-Atlantic Ridge
Harry Hess
Discovered seafloor
spreading
Evidence of Seafloor
spreading
Rocks along rift
areas were younger
than those farther
away. New lava
rocks were being
laid on either side of
the rift
Magnetic reversals of
the iron bearing basaltic
rocks of the sea floor.
As the new rock was
formed the iron particles
in the rock aligned
themselves with the
magnetic poles of the
earth at that time
Plate Tectonics
Earth’s crust and upper
mantle are separated
into plates.
Plates float on the
mantle.
Make contact with each
other.
Cause earthquakes and
volcanoes, mountains
Composition of plates
Crust and upper
mantle – lithosphere
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Less dense layer
floats on more dense
layer
Asthenosphere –
mantle
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More dense
Plates flow on this
Plate Boundaries
Divergent
Boundaries
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Move away from
each other
mid-Atlantic Ridge
Great Rift Valley in
eastern Africa
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Great Rift Valley of
Africa
Convergent Plates
Plates that come
together.
1. Ocean/continental
the ocean sinks below the
continent.
remelts in mantle
Subduction zone- where
ocean plate goes under
continental plates
Volcanoes form here.
Andes Mts.
Oceanic-Oceanic Convergence
2. Ocean/ocean
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One ocean plate
subducts under
another and melts.
Forms deep sea
trenches
Forms an island arc
volcano
Japan
Island arcs – two
ocean plates collide
and one subducts to
remelt lithosphere to
cause volcanoes in
the ocean floor.
Ex. Japan
Deep sea trench –
forms where
subducted plate
melts into the
mantle.
Ex. Mariana Trench
Pacific Ocean
3. Continental/
continental
- collision between
plates cause the
boundaries to crumble
forming mountain
ranges.
- earthquakes formed
- Himalayan Mts
formed
Transform Fault
Boundary
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Two plates slip past
one another
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Moving in opposite
directions
Moving in same
direction at different
rates
Earthquakes occur
San Andreas Fault
Transform fault
Earthquakes formed
Causes of plate
tectonics
Convection
currents
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Hot less dense
asthenosphere rises
Cools – more dense
drops
Reheats cycle
begins again
Effects of plate
tectonics
Volcanoes
Earthquakes
Mountain building
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FAULT/BLOCKCompression forces
fault causes
weakness. Part of
the land drops.
Leaving behind higher
ground.
Ex. Sierra Nevadas.
http://glencoe.mcgrawhill.com/sites/dl/free/0078617006/164213/00038307.html
Folded mountains
Two plates collide with
each other.
Ex. Appalachian Mts.
Anticline – upward fold
in rocks
Syncline – downward
fold in rocks.
Strike-slip Faults –
plates moving past
each other.
Snag onto each
other storing up
stress
Ex. San Andreas
Fault
Strike slip fault
Rio Grand Rift
Rio Grand Rift
Found from
Colorado, New
Mexico and Texas
Hidden underground
below sediment and
basalt
Wrangell Mountains
Alaska
Wrangell Mt. Alaska
Formed on floor of the Pacific ocean
9600 km from present location
Theory; they were scraped off ocean
plate as it was subducted
Red Sea
Formed due to
divergence along a
triple junction of the
Great Reft Valley in
Africa and the Gulf
of Aden.
Page 113 Critical
thinking
Section: 3 page 289
1, 2, 3, 4,
Page 294
Vocab
Checking concepts
Thinking Critically
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15,16, 17, 18, 20
23,24, 25