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

The Earth’s surface is broken into plates

The Earth’s surface is broken into plates

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

3

4

5

6

HawaiiHawaii

EasterEaster

Galapagos

Galapagos

SamoaSamoa

The Hawaiian HotspotThe Hawaiian Hotspot

Volcanoes to atolls (Darwin)

Volcanoes to atolls (Darwin)

Tahiti -- shield volcanoTahiti -- shield volcano

Moorea -- fringing reefMoorea -- fringing reef

Raiatea - barrier reef Raiatea - barrier reef

Bora Bora -- lagoonBora Bora -- lagoon

Maupiti -- the oldest volcano

next stage is the coral atoll

Maupiti -- the oldest volcano

next stage is the coral atoll

French Polynesia from space

French Polynesia from space

atollatoll

barrier reeffringing reef

Pacific Hotspot Volcanic Chains

Pacific Hotspot Volcanic Chains

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

JOIDES Resolution drillshipJOIDES Resolution drillship

Reunion hotspot track, central Indian

Ocean

Reunion hotspot track, central Indian

Ocean

“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?

Impact Site: Yucatan PeninsulaImpact Site: Yucatan Peninsula

Volcanic catastrophes and Mass Extinctions

Volcanic catastrophes and Mass Extinctions

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 PlumesMantle Plumes

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

Which is not a hotspot? Which is not a hotspot?

Iceland

Hawaii

Yellowstone

Mt. St. Helens

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

Laki, Iceland (1783) -- the year without a summer

Laki, Iceland (1783) -- the year without a summer

Laki, Iceland (1783) -- the year without a summer

Laki, Iceland (1783) -- the year without a summer

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

Hydrothermal Plumes from LIPs

Hydrothermal Plumes from LIPs

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

Two Styles of Mantle Convection

Two Styles of Mantle Convection

Evolution of LifeEvolution of Life

• “Punctuated” by rapid change events

• Where there is chaos there is opportunity

• Extinctions lead to new ecosystems

• “Punctuated” by rapid change events

• Where there is chaos there is opportunity

• Extinctions lead to new ecosystems