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Hotspots, Plumes and Mass Extinctions. Is Hawaii more than a great vacation spot? How does life respond to geologic catastrophes?. Plate Tectonics - Distribution of Volcanic and Earthquake Activity. The Earth’s surface is broken into plates. 1. Wilson Cycle (ocean basin fm). 2. Examples:

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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?

wilson cycle ocean basin fm


Wilson Cycle (ocean basin fm)



1. East African Rifts

2. Red Sea

3. Atlantic Ocean

4. Pacific Ocean

5. Mediterranean Sea

6. Himalayas, Tibet





french polynesia from space
French Polynesia from space


fringing reef

barrier reef

  • Where do Hotspots come from?
  • How do Hotspots start?
  • How long do they last?
indian ocean
Indian Ocean
  • Hotspot tracks and 3 spreading ridges
  • A complete record of hotspot activity
western india
Western India
  • 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?
  • Birth of the Iceland hotspot
  • Next came the opening of the North Atlantic Ocean basin

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
mantle plumes
Mantle Plumes
  • Part of the circulation in the Mantle
  • Driven by temperature differences
  • Hot and cold => density differences
  • Gravity Rules!
mantle convection the driving force for plate tectonics
Mantle convection - the driving force for plate tectonics

What causes the warmer material to rise?

mantle convection and hotspot formation

Cross-sections of the Earth

Mantle convection and hotspot formation

Red = hot upwelling from core-mantle


Blue = cold downwelling

Cold lithosphere sinks, hot plumes rise.

Computer Model

Cartoon Schematic

which is not a hotspot
Which is not a hotspot?




Mt. St. Helens

degassing magma
Degassing Magma
  • Gases include CO2, SO2, Cl, F that make “acid rain”
  • Shuts down photosynthesis
ocean anoxic events productivity or preservation
Ocean Anoxic Eventsproductivity or preservation?

Marine sedimentary layers exposed in Italy

effects of submarine plateaus
Effects 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
evolution of life
Evolution of Life
  • “Punctuated” by rapid change events
  • Where there is chaos there is opportunity
  • Extinctions lead to new ecosystems