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

Wilson Cycle (ocean basin fm) 1 2 Examples: 1. East African Rifts 2. Red Sea 3. Atlantic Ocean 4. Pacific Ocean 5. Mediterranean Sea 6. Himalayas, Tibet 3 4 5 6

Hawaii

Easter

Galapagos

Samoa

The Hawaiian Hotspot

Volcanoes to atolls (Darwin)

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 fringing reef barrier reef

Pacific Hotspot Volcanic Chains

Questions: Where do Hotspots come from? How do Hotspots start? How long do they last?

Indian Ocean Hotspot tracks and 3 spreading ridges A complete record of hotspot activity

JOIDES Resolution drillship

Reunion hotspot track, central Indian Ocean

“flood” basalts in western India >300 lava flows, each 1000 km3

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) What killed the Dinosaurs? 65 million yr ago A meteorite, or volcanic activity, or BOTH? Mass Extinction (K-T Boundary)

Impact Site: Yucatan Peninsula

Volcanic catastrophes and Mass Extinctions

Greenland Birth of the Iceland hotspot Next came the opening of the North Atlantic Ocean basin

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: BIG!! NOT explained by Plate Tectonics Initial Plume and Hotspot Activity

Mantle 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

Mantle convection - the driving force for plate tectonics What causes the warmer material to rise?

Mantle Plumes

Mantle convection and hotspot formation Cross-sections of the Earth Red = hot upwelling from core-mantle boundary Blue = cold downwelling Cold lithosphere sinks, hot plumes rise. Cartoon Schematic Computer Model

Which is not a hotspot? Yellowstone Iceland Hawaii Mt. St. Helens

Degassing Magma 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

Submarine: Hydrothermal Exchange – Release of Metals

Ocean Anoxic Events productivity or preservation? Marine sedimentary layers exposed in Italy

Hydrothermal Plumes from LIPs

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

Two Styles of Mantle Convection

Evolution of Life “Punctuated” by rapid change events Where there is chaos there is opportunity Extinctions lead to new ecosystems