Download Plate tectonics

Internal processes:
Plate tectonics
Reading:
This week: Ch 3
Next week: Ch 4
Environmental Geology – Plate tectonics
The Earth’s
magnet
Normal polarity
Magnetic azimuth
• the compass needle
points north
Magnetic dip
•
at equator: 0 (horizontal)
•
at pole: 90 deg (vertical)
Î tells us about the latitude
when the rooks cooled
Environmental Geology – Plate tectonics
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The Earth’s
magnet
Reverse polarity
Magnetic azimuth
• the compass needle
points south
Magnetic dip
•
at equator: 0 (horizontal)
•
at pole: 90 deg (vertical)
Î tells us about the latitude
when the rooks cooled
Environmental Geology – Plate tectonics
Plate tectonics:
Reconstructing
plate motion
The magnetic tape recorder:
Given the oceanic record we can wind
back the plates to see how the plates
have been moving.
This shows us how Pangaea broke up.
Environmental Geology – Plate tectonics
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Plate tectonics:
Continental magnetization
Environmental Geology – Plate tectonics
Plate tectonics:
Plate motion further back in time
Environmental Geology – Plate tectonics
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QUESTION
Plate tectonics:
The formation of Pangaea
When we add the continental plate motion recoded we can
extend plate reconstruction back beyond 200Ma
i.e. prior to the break-up of Pangaea
Environmental Geology – Plate tectonics
Earth’s interior:
Properties of geological materials
How can plates move across the Earth’s surface?
Î The Earth is not a rigid solid, but a plastic solid.
Environmental Geology – Plate tectonics
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Earth’s interior:
Properties of geological materials
How can plates move across the Earth’s surface?
Î The Earth is not a rigid solid, but a plastic solid.
Plastic
deformation:
Ductile flow
Brittle
failure:
Rupture
Environmental Geology – Plate tectonics
Earth’s interior:
An overview
Environmental Geology – Plate tectonics
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Plate tectonics:
Categories of
plate boundaries
Divergent
• Established mid-ocean ridge
• New rift zone, new ocean
Transform
• Along mid-ocean ridges
• Across continents
Convergent
• Ocean – continent
• Ocean – ocean
• Continent – continent
Environmental Geology – Plate tectonics
Plate tectonics:
Categories of
plate boundaries
Divergent
• Established mid-ocean ridge
• New rift zone, new ocean
Mid-Atlantic Ridge
East African Rift
Transform
• Along mid-ocean ridges
• Across continents
Fracture Zones e.g. south Pacific
San Andreas Fault
Convergent
• Ocean – continent
• Ocean – ocean
• Continent – continent
Off west coast of South America
Japan Trench, western Pacific
Himalaya
Environmental Geology – Plate tectonics
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Divergent boundaries:
Mid-Atlantic Ridge
Environmental Geology – Plate tectonics
Divergent boundaries:
Mid-ocean ridge resources
Black smokers produce rich mineral
deposits …at 2.5 km depth
Environmental Geology – Plate tectonics
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Divergent boundaries:
The East African Rift
and Red Sea
Environmental Geology – Plate tectonics
Divergent plate boundaries:
The Red Sea
Environmental Geology – Plate tectonics
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Divergent plate boundaries:
Oil at the continental margin
The continental rifting
process provides the
right environment for
oil formation within
continental margin
sediments
Environmental Geology – Plate tectonics
Transform plate boundaries:
Ocean transforms
Ocean bathymetry map
Mid-ocean
ridges are
offset by
ocean
transforms:
Fracture
Zones
Environmental Geology – Plate tectonics
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Transform plate boundaries:
Ocean transforms
Environmental Geology – Plate tectonics
Transform plate boundary:
San Andreas Fault
Environmental Geology – Plate tectonics
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Transform plate boundary:
San Andreas Fault
Environmental Geology – Plate tectonics
Convergent plate boundaries:
Different types
Environmental Geology – Plate tectonics
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Convergent plate boundaries:
South America
Environmental Geology – Plate tectonics
Convergent plate boundaries:
Different types
Environmental Geology – Plate tectonics
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QUESTION
Convergent plate boundaries:
India and Asia – the Himalaya
Environmental Geology – Plate tectonics
The Ring of Fire
Refers to the
concentration of
earthquakes and
volcanoes around
the Pacific rim.
Environmental Geology – Plate tectonics
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Plate tectonics:
Determining plate velocities
1. Magnetic stripes on the ocean floor
2. Hotspot tracks record plate motion
Environmental Geology – Plate tectonics
Plate tectonics:
Hotspot tracks
Strings of volcanic ocean islands recording the motion of the plate
Hawaiian chain
The formation process
Environmental Geology – Plate tectonics
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Plate tectonics:
Global hotspot tracks
Environmental Geology – Plate tectonics
Plate tectonics:
Plate velocities
Environmental Geology – Plate tectonics
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Plate tectonics:
The unifying theory
Plate tectonics:
Recognizes that rigid plates are moving
across the Earth’s surface.
A unifying theory:
A single theory that explains a large body
of evidence.
Other examples:
Physics – theory of relativity
Chemistry – nature of a chemical bond
Astrophysics – the Big Bang
Biology – DNA
Geology – plate tectonics
Environmental Geology – Plate tectonics
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