Download 2 - Tectonic Plates - UTEP Geological Sciences

Plate Tectonics
Linking Observations
Pacific Ring of Fire
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Linking Observations
Alfred Wegener (1912)
Continental Drift
Continental Drift Hypothesis
- The concept of continental movement was first
suggested when it was noticed that Africa and
South America had coastlines which appeared to
be counterparts of one another
- This suggested they may once have been joined
and drifted apart
- He postulated that all landmasses were originally
united into a supercontinent named Pangaea.
- Pangaea consisted of a northern landmass
called Laurasia and a southern landmass called
Gondwana
- As Pangaea broke up, the various continents
moved to their present-day locations.
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What is the Evidence for Continental Drift?
1. Similarity of Rock Sequences and
Mountain Ranges
–  Marine, nonmarine, and
glacial rock sequences
of Pennsylvanian to
Jurassic age are nearly
identical on all the
Gondwana continents
What is the Evidence for Continental Drift?
2. Glacial Evidence
–  Glacial tills and striations
on the bedrock beneath
the till provide evidence
of glaciation at the same
time on all the
Gondwana continents,
with South Africa located
at the South Pole.
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What is the Evidence for Continental Drift?
3. Fossil Evidence
–  Some of the most
compelling evidence
comes from fossils like
the Glossopteris fern.
–  One of the strongest
examples is the
Mesosaurus, a fresh
water reptile.
What is the Evidence for Continental Drift?
4. Paleomagnetic studies
–  Paleomagnetismis the
remnant magnetism in
ancient rocks recording the
direction and intensity of
Earth’s magnetic field at
the time of the rock’s
formation.
–  The continents had moved
over time. If the continents
were moved into different
positions relative to each
other, the separate poles
could be resolved into one.
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Plate Tectonics Theory
Plate Tectonics Theory
Lithosphere (solid)
Asthenosphere
(liquid)
(solid)
(mostly liquid)
(liquid)
(solid)
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Plate Tectonics Theory
Plate Tectonics Theory
- According to plate
tectonic theory, the rigid
lithosphere (crust +
upper most mantle), is
divided into differentsized plates (tectonic
plates) that drive on top
of the liquid
asthenosphere (mantle)
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Plate Tectonics Theory
- A convective cell heat system is the basic process
responsible for plate motion.
Plate Boundaries
Plate 3
Plate 4
Plate 5
Plate 6
Plate 2
Plate 1
1.  Divergent
2.  Convergent
3.  Transform
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1. Divergent Plate Boundaries
-Plates move away from one another.
-Most divergent boundaries occur along
the crests of oceanic ridges
- New oceanic lithosphere is formed at
the opening rift. These geologic regions
are called Mid-Ocean ridges.
2. Convergent Plate Boundaries
- Convergent boundaries
are places where two
plates collide.
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- Lithosphere is molted and
destroyed
-  Cause the strongest
earthquakes
-  The geologic regions
where a oceanic plate
bends and slides
underneath a continental
plate are called
Subduction Zones and
cause very deep
Oceanic Trenches.
-  The deepest place on
Earth is the Mariana
Trench (~11 km depth)
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Transform Plate Boundary
These are boundaries along
which plates slide laterally past
each other along transform
faults
strike-slip
faulting
Rio Grande rift
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