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Hotspots, Plumes and Mass Extinctions
Hotspots, Plumes and Mass Extinctions
Is Hawaii more than a great vacation spot?How does life respond to geologic
catastrophes?
Is Hawaii more than a great vacation spot?How does life respond to geologic
catastrophes?
Plate Tectonics - Distribution of Volcanic and Earthquake ActivityPlate Tectonics - Distribution of
Volcanic and Earthquake Activity
Wilson Cycle (ocean basin fm)
Wilson Cycle (ocean basin fm)
Examples:1. East African Rifts2. Red Sea3. Atlantic Ocean4. Pacific Ocean5. Mediterranean Sea6. Himalayas, Tibet
Examples:1. East African Rifts2. Red Sea3. Atlantic Ocean4. Pacific Ocean5. Mediterranean Sea6. Himalayas, Tibet
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2
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Maupiti -- the oldest volcano
next stage is the coral atoll
Maupiti -- the oldest volcano
next stage is the coral atoll
Questions:Questions:
• Where do Hotspots come from?• How do Hotspots start?• How long do they last?
• Where do Hotspots come from?• How do Hotspots start?• How long do they last?
Indian OceanIndian Ocean
• Hotspot tracks and 3 spreading ridges
• A complete record of hotspot activity
• Hotspot tracks and 3 spreading ridges
• A complete record of hotspot activity
“flood” basalts in western India>300 lava flows, each 1000 km3
“flood” basalts in western India>300 lava flows, each 1000 km3
Western India
Western India
• An accumulation of lava flows 5 km thick!
• Occurred at the same time as the extinction of the dinosaurs
• An accumulation of lava flows 5 km thick!
• Occurred at the same time as the extinction of the dinosaurs
Mass Extinction
(K-T Boundary)
Mass Extinction
(K-T Boundary)
• What killed the Dinosaurs?
• 65 million yr ago• A meteorite, or
volcanic activity, or BOTH?
• What killed the Dinosaurs?
• 65 million yr ago• A meteorite, or
volcanic activity, or BOTH?
GreenlandGreenland• Birth of the
Iceland hotspot• Next came the
opening of the North Atlantic Ocean basin
• Birth of the Iceland hotspot
• Next came the opening of the North Atlantic Ocean basin
Global Distribution of large, rapidly-erupted volcanic
events
Global Distribution of large, rapidly-erupted volcanic
events
red = hotspot-related volcanism since 250 Ma
Columbia River Basin Flood Basalts with source at Yellowstone
Flood basalts, India
Large Igneous Provinces are:
Large Igneous Provinces are:
• BIG!!• NOT explained by Plate Tectonics• Initial Plume and Hotspot Activity
• BIG!!• NOT explained by Plate Tectonics• Initial Plume and Hotspot Activity
Mantle PlumesMantle Plumes
• Part of the circulation in the Mantle• Driven by temperature differences• Hot and cold => density differences• Gravity Rules!
http://www.youtube.com/watch?v=f37Gf6IVj6o&feature=related
• Part of the circulation in the Mantle• Driven by temperature differences• Hot and cold => density differences• Gravity Rules!
http://www.youtube.com/watch?v=f37Gf6IVj6o&feature=related
Mantle convection - the driving force for plate tectonicsMantle convection - the driving force for plate tectonics
What causes the warmer material to rise?
Mantle convection and hotspot formation
Mantle convection and hotspot formation
Cold lithosphere sinks, hot plumes rise.
Red = hot upwelling from core-mantleboundary
Blue = cold downwelling
Computer ModelCartoon Schematic
Cross-sections of the Earth
Degassing Magma
Degassing Magma
• Gases include CO2, SO2, Cl, F that make “acid rain”
• Shuts down photosynthesis
• Gases include CO2, SO2, Cl, F that make “acid rain”
• Shuts down photosynthesis
Submarine: Hydrothermal Exchange – Release of Metals
Submarine: Hydrothermal Exchange – Release of Metals
Ocean Anoxic Eventsproductivity or preservation?
Ocean Anoxic Eventsproductivity or preservation?
Marine sedimentary layers exposed in Italy
Marine sedimentary layers exposed in Italy
Effects of Submarine PlateausEffects of Submarine Plateaus
• 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 “benthic” marine organisms
• 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 “benthic” marine organisms