Download Plate Tectonics and Geology

Plate Tectonics and
Geology
Genesis of Earth
Earth is 4.6 billion years old.
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Same age as all other planets and the sun.
Earth formation.
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Nebular hypothesis. Diffuse cloud of matter
rotating in space, formed a disk shaped body,
which later formed into sun and planets. Planets
are cooled and condensed gases that surrounded
the sun.
Core Development
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Earth was a homogeneous planet immediately after
formation
But then, a profound reorganization as Earth initially
heated up due to
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collision with other rocky bodies
heat of compression
Radioactive decay of elements
Earth heated up such that much of the interior melted
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causing dense elements like iron and nickel to sink to the core
lighter elements like silicon and aluminum float to the crust
Resulted in a stratified Earth - core, mantle, crust
Distribution of Elements
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More than 100 elements in entire Earth, but
99% of Earth's mass is made up of only 8
elements
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Whole Earth:
Fe>O>Si>Mg>Ni>S>Ca>Al (others constitute < 1%)
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Earth's crust
O>Si>Al>Fe>Mg>Ca>K>Na (other constitute <1%)
Composition of Earth’s Crust
Earth’s Crust
Oxygen 46.6%
All others 1.5%
Magnesium 2.1%
Silicon 27.7%
Potassium 2.6%
Sodium 2.8%
Calcium 3.6%
Iron 5.0%
Fig. 10.4, p. 213
Aluminum 8.1%
Layers of the Earth
crust
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Crust
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The surface of the
Earth is a very thin
layer made of rocks,
minerals and clay
We live on the crust
of the earth
Layers of the Earth
crust
mantle
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Mantle- Upper and
Lower
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The mantle is the
biggest part of the
earth; the magma is rich
in iron and magnesium
Convection occurs here
and is thought to drive
plate tectonics
Layers of the Earth
crust
mantle
Outer
core
•Outer Core
•The outer core
consists of molten
iron and magma
•The outer core
rotates giving the
Earth a magnetic
field
Layers of the Earth
crust
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Inner Core
mantle
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Outer
core
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Inner
Core
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The inner core is made
of solid iron
The closest model of
the inner core we have
is an iron nickel
meteorite
The inner core is under
extreme pressure
How do we know about the layers of
the Earth?
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To date, humans have
never drilled through the
crust of the Earth.
Scientists study where
waves from earthquakes
end up around the globe.
The waves move
differently through
different densities of
material.
GEOLOGIC PROCESSES
Spreading
center
Collision between
two continents
Subduction
zone
Continental
crust
Ocean
trench
Oceanic
crust
Oceanic
crust
Continental
crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Mantle
convection
cell
Two plates move
towards each other.
One is subducted
back into the mantle
on a falling convection
current.
Hot
material
rising
through
the
mantle
Mantle
Hot outer
core Inner
core
The Earth’s Major Tectonic Plates
JUAN DE
FUCA PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
AFRICAN PLATE
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
NAZCA PLATE
PLATE
SOMALIAN
SUBPLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
INDIAAUSTRALIAN
PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform
faults
The Earth’s Major Tectonic Plates
Hawaiian Island Hot Spot
How the hotspot works
History of Continental Drift
Hypothesis
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1596 Abraham Ortelius: fit of South American & African
coasts
1620 Francis Bacon: noted same fit
1782 Benjamin Franklin: suggested that crust of Earth
"floated" on fluid interior (crust broken and disordered by
movement of fluids)
1885 Edward Suess
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Similarities between Late Paleozoic plant fossils of Africa, India, South
America, Australia & Antarctica
Carboniferous glaciers on Africa, S. America, Australia, Inda
Southern supercontinent of Gondwana
Gondwana named after province in India where there was glacial and
plant evidence (Glosopteris flora)
Landbridges, which sank beneath the sea, connected present continent
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Continental movement not a new idea
Wegener developed hypothesis of "continental
drift”.
Proposed "continental drift" - published "Origin of
Continents and Oceans" in 1915
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Pangaea ("all land") existed about 200 Ma
Showed breakup in series of maps
Few supporters - mostly European and African geologists
Ridiculed by American geologists
Can't "sail" continents through oceans (granitic continents
too weak to move through stronger basaltic crust
No mechanism to explain movement (Wegener's tidal
forces => too weak)
Land bridges the answer to explain fossils