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WELCOME
TO
PLANET EARTH
~4.6 BILLION YEARS OLD
Inner Core: Solid inner core made up of Iron (Fe) and Nickel (Ni)
• Solid due to tremendous pressure
Outer Core: molten outer core made up of Iron (Fe) and Sulfur (S)
• Semi-solid due to lower pressures
Mantle: mostly solid rock
• Upper area called Asthenosphere- slowly flowing rock
Lithosphere: thin, rigid layer of rock
• Outermost layer of the earth
• CONTAINS rigid upper mantle and the crust- our solid surface of the
earth.
The Lithosphere floats atop the asthenosphere ---like a cracker on a
layer of pudding.
• Lithosphere moves and breaks
into pieces called
TECTONIC PLATES
• ~dozen tectonic plates moving
independently from one
another
• Earth sits on 6 giant plates,
rest are under the ocean and
continents.
Two Types of Plates
1.Oceanic
2. Continental
• Under oceans
• Under continents
• Thin
• Thick
• Dense and Heavy
• Lighter
• Always Sinks under
• Never Sinks
Plate boundaries: edges of the plates
Places where two plates touch is where events like
earthquakes, volcanoes, sea spreading, and mountains
occurs
1.Convergent Boundary
2.Divergent Boundary
3.Transform Fault Boundary (or just transform)
Divergent
(sea floor spreading)
Convergent
(with subduction)
Transform
(San Andreas Fault)
Boundaries Summarized
Divergent
Convergent
(normal/constructive)
(reverse/destructive)
•plates are moving
apart
•plates are coming
together
Transform
(strikeslip/conservative)
•plates are slipping
past each other
•crust is not created
or destroyed
•new crust is created
•Magma is coming to
the surface
• No volcanism
•crust is returning
to the mantle
Divergent: Sea Floor Spreading
• Mid Atlantic Ocean Ridge
• longest topographic feature on Earth (70,000 km!)
• 2-3 km above ocean basins
Divergent: Sea Floor Spreading
Pillow Lava Rocks
under water, marine hotspot volcano chains and the constructive
plate boundaries of mid-ocean ridges
Transform Faults
• Plates move past each
other
• strike slip faults
Example:
The San
Andreas Fault California
3 Types of plate Collisions
Oceanic
Vs
Continental
Oceanic subducts or Sinks
Continental
Vs
Continental
No Subduction (mountain
formed)
Oceanic
Vs
Oceanic
One will subducts or Sinks
(heaviest)
Convergent Plate Boundaries
• Ocean-Continent collision
• oceanic always subducts or sinks
under continental
Examples:
Nazca plate
vs.
South American plate
(forming the Andes)
Convergent Plate Boundaries
• Continent-Continent
collision
• No Subduction
Example:
Indian plate
v.s.
Eurasian plate
(forming the Himalayas,
Mt. Everest)
Convergent Plate Boundaries
• Ocean-Ocean collision
• One of them always subducts or sinks
Magma
• molten material beneath the Earth’s crust.
• collects in a magma chamber beneath a volcano,
and can then be injected into cracks in rocks or
issue out of volcanoes in eruptions.
• temperature of magma ranges between 700 C and
1300 C.
When it reaches the surface and comes out of a volcano,
magma becomes Lava.
So the different between magma and lava is location.
Magma is deep underground, in chambers beneath
volcanoes, and lava is the stuff that comes out of
volcanoes.
Post-Pangea movement is supported by evidence,
including:
1.Palaeo-magnetism
• When hot magma rises to the earth's surface
and cools, the minerals themselves (especially
magnetite) become magnetized in alignment
with the Earth's magnetic field.
2.Palaeontology
• Fossil evidence
3.Geological fit
• continents seemed to fit together
https://www.youtube.com/watch?v=yEYy_nVC4L0
Evidence that the Ocean Floor is Spreading
• Magnetic Bands Reversals
•
•
•
•
•
Lava comes up along ridge lines (mostly underwater) as plates separate.
In 76 million years there’ve been 171 reversals of the earth’s magnetic field.
Lava contains iron.
Cooling lava locks in the prevailing magnetism.
The ocean floor near the ridges has the prevailing field and the floor further from the
ridges shows field reversals: evidence that the ocean floor is spreading.
• Rocks and fossils dating
• Older as one moves away from ridges
• Youngest rock is next to the ridge
Earth's Magnetic Field (General)
Magnetic field reversal
• Proves the
Earth magnetic field reverses itself every 27000 years
• Another proof that the sea floors are spreading
Age of sea floor as measured by fossils
- Older as one moves away from ridges
- Youngest rock is next to the ridge
Hot Spot Formation of Hawaii
The Pacific Ring Of Fire
• A collection of earthquakes and volcanoes that make a ring around
the Pacific ocean
• It shows the inter-relation of plate tectonics