Transcript Lecture 7. Marine Sediments - The Cyberworld of Deepsea

Music today: The Ventures,
“Hawaii Five-O”
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Reminder: 1st Midterm Exam next
Wednesday (April 20)
In class, closed book
70% multiple choice; 30% short essay
Study Guide is up on website
Lecture 8: Hotspots, Plumes and
LIPs (Large Igneous Provinces)
Is Hawaii more than a good vacation spot?
How does life respond to catastrophes?
Plate Tectonics - Distribution of
Volcanic and Earthquake Activity
Wilson Cycle (of
ocean basin fm)
Examples:
1. East African Rifts
2. Red Sea
3. Atlantic Ocean
4. Pacific Ocean
5. Mediterranean Sea
6. Himalayas, Tibet
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The Hawaiian Hotspot
Tahiti -- shield volcano
Moorea -- fringing reef
Raiatea - barrier reef
Bora Bora -- lagoon
Maupiti -- the oldest volcano
next stage is the coral atoll
French Polynesia from space
atoll
barrier reef
fringing reef
Hotspot Volcanic Chains
Questions:
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Where do Hotspots come from?
How do Hotspots start?
How long do they last?
Indian Ocean
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Hotspot tracks
and 3 spreading
ridges
A complete record
of hotspot activity
JOIDES Resolution drillship
Western
India
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An accumulation
of lava flows 3
miles thick!
Occurred at the
same time as the
dinosaurs’
extinction
Mass Extinction
(K-T Boundary)
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What killed the
Dinosaurs?
65 million yr ago
A meteorite, or
volcanic activity,
or BOTH?
Impact Site: Yucatan Peninsula
Volcanic catastrophes and Mass
Extinctions
Greenland
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Birth of the
Iceland hotspot
Next came the
opening of the
North Atlantic
Ocean basin
Global Distribution of LIPs
Large Igneous Provinces are:
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BIG!!
NOT explained by Plate Tectonics
Initial Plume and Hotspot Activity
A Mantle Plume
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A blob of warm
material rising from
the lower mantle
Solid but flowing at
slow rate (<1 m/yr)
Degassing Magma
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Gases include CO2,
SO2, Cl, F that make
“acid rain”
Shuts down
photosynthesis
Hydrothermal Exchange - Metals
Effects of Submarine Plateaus
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Release of “reduced” metals uses up
oxygen in the oceans
Trace metals are “nutrients”, so
promote rapid growth of plankton
Sinking organic matter also uses up
oxygen in the oceans
Extinctions of marine organisms
Two Styles of Mantle Convection
Evolution of Life
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Where there is
chaos there is
opportunity
Extinctions lead to
new ecosystems