Scribd
Upload
37 views25 pages

Plate Tectonics

The document summarizes plate tectonics and the evidence that supports the theory of continental drift. It describes how Wegener originally proposed that the continents were once joined together in a supercontinent called Pangaea that later broke apart. It discusses the evidence Wegener provided including fossil matches and matching rock formations between continents. It then explains how most scientists originally rejected Wegener's hypothesis because he could not explain how the continents moved. The emergence of the theories of seafloor spreading proposed by Harry Hess and the discovery of mid-ocean ridges provided the mechanism of plate tectonics to explain the movement of continents. It defines the three types of plate boundaries and provides examples of each: divergent, convergent and transform

Uploaded by

michaeldevid7890
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
37 views25 pages

Plate Tectonics

The document summarizes plate tectonics and the evidence that supports the theory of continental drift. It describes how Wegener originally proposed that the continents were once joined together in a supercontinent called Pangaea that later broke apart. It discusses the evidence Wegener provided including fossil matches and matching rock formations between continents. It then explains how most scientists originally rejected Wegener's hypothesis because he could not explain how the continents moved. The emergence of the theories of seafloor spreading proposed by Harry Hess and the discovery of mid-ocean ridges provided the mechanism of plate tectonics to explain the movement of continents. It defines the three types of plate boundaries and provides examples of each: divergent, convergent and transform

Uploaded by

michaeldevid7890
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 25

Plate Tectonics

Continental Drift
Wegener’s continental drift hypothesis
stated that the continents had once been
joined to form a single supercontinent.

• Wegener proposed that the supercontinent,


Pangaea, began to break apart 200 million
years ago and form the present landmasses.
Continental Drift
Evidence:
1. Jig-Saw Fit
• Continents fit together like Puzzle pieces
2. Fossil Evidence
• fossils of same age and species were found in
connecting bands on different continents
3. Rock Types and Structure
• Similar bands of rocks types and mountain belts
connect
4. Ancient Climates
5. PANGAEA!
Connecting Mountain
Ranges
The Earth
Rejecting the Hypothesis
• Most scientists rejected Wegener’s
ground breaking hypothesis because he
could not provide an explanation of how
the plates moved
• A NEW THEORY EMERGES!
Seafloor Spreading
• In Wegener’s theory, continents
“plowed” through the sea like bull-
dozers.
– Not the case. Continents are actually
connected to plates, which move
• Continents actually move with
lithospheric plates that are pushed by
Mid-Ocean ridges
Harry Hess
• Discovered “Mid-Ocean Ridges
– Spreading centers for tectonic plates
• Noticed magnetic stripes on the ocean
floor which proved that new crust was
being created at these ocean ridges
• Provided the mechanism for how the
plates moved.
Topographic Map of the
World
Plate Tectonics
• The theory explaining how the movements of
earth’s “TECTONIC PLATES” or “moving
plates” create the geologic events like
earthquakes, volcanoes and tsunamis.
• Lithospheric Plates- giant puzzle pieces
connecting on the surface of earth.
– These sit on top of mantle so they can move
around
Plate Boundaries
• Three types:
– Divergent Boundary
– Convergent Boundary
– Transform Boundary
Divergent Boundary
Convergent Boundaries
• Two plates crashing together
• Collliding
• Three types:
– Continental to Continental
– Ocean to Ocean
– Ocean to Continental
Continent to Continent
collision
• When two continents collide, you will get mountain
ranges (Example: Himalayans where India crashing
into Asia).
Continent to Continent
collision
Ocean to Ocean
Convergance
• Two oceanic slab converge together. One is
pulled under the other
• Often forms volcanoes on seafloor
– Volcanic Island Arcs
• Aleutian Islands
– Alaska
Ocean to Ocean
Convergent
• Aleutian Island, Alaska, US
Ocean to Continental
Convergance
• ALSO KNOWN AS SUBDUCTION ZONE
• Oceanic plate is forced down into the mantle
beneath a second continental plate
• Creates volcanoes and deep ocean trenches
– Examples Andes and Marianna Trench
– Marianna Trench is deepest place in the WORLD!
35,000 feet deep!!!!!
Subduction Zone
Subduction Zone
process
• Denser ocean slab pulled underneith
continent
• As it is pulled under, the oceanic crust
begins to melt.
• When crust begins to melt, magma rises
• Magma rises to surface and creates
volcanoes
Transform Boundaries
• Plates grind past each other without
destroying or creating new lithosphere
• Like cars passing each other on a highway
• Creates tremendous earthquakes
• Example: San Andreas Fault
Transform Boundaries
How do Plates Move?
• The crust lies on top of the mantle.
• It is believed that convection currents cause
movement in the asthenosphere. Heat rises from
interior.
• Areas where the asthenosphere is raising causes
plates to move apart (diverge) and areas where the
asthenosphere is sinking causes plates to move
together (converge).
Why do plates move?
• Clear answer is yet unknown
• There are theories for “Ridge Push”,
“Trench Suction”, and just plain old
“Gravity”
Hotspot (non tectonic)
Hawaiian–Emperor seamount chain

You might also like