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Hotspots, Plumes and Mass Extinctions

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Presentation on theme: "Hotspots, Plumes and Mass Extinctions"— Presentation transcript:

1 Hotspots, Plumes and Mass Extinctions
Is Hawaii more than a great vacation spot? How does life respond to geologic catastrophes?

2 Plate Tectonics - Distribution of Volcanic and Earthquake Activity

3 The Earth’s surface is broken into plates

4 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


6 Hawaii

7 Easter

8 Galapagos

9 Samoa

10 The Hawaiian Hotspot

11 Volcanoes to atolls (Darwin)

12 Tahiti -- shield volcano

13 Moorea -- fringing reef

14 Raiatea - barrier reef

15 Bora Bora -- lagoon

16 Maupiti -- the oldest volcano next stage is the coral atoll

17 French Polynesia from space
atoll fringing reef barrier reef

18 Pacific Hotspot Volcanic Chains

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

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

21 JOIDES Resolution drillship

22 Reunion hotspot track, central Indian Ocean


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

25 Western India An accumulation of lava flows 5 km thick!
Occurred at the same time as the extinction of the dinosaurs

26 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)

27 Impact Site: Yucatan Peninsula

28 Volcanic catastrophes and Mass Extinctions

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

30 Global Distribution of large, rapidly-erupted volcanic events

31 red = hotspot-related volcanism since 250 Ma
Columbia River Basin Flood Basalts with source at Yellowstone Flood basalts, India

32 Large Igneous Provinces are:
BIG!! NOT explained by Plate Tectonics Initial Plume and Hotspot Activity

33 Mantle Plumes Part of the circulation in the Mantle
Driven by temperature differences Hot and cold => density differences Gravity Rules!

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

35 Mantle Plumes

36 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

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

38 Degassing Magma Gases include CO2, SO2, Cl, F that make “acid rain”
Shuts down photosynthesis

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

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

41 Submarine: Hydrothermal Exchange – Release of Metals

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

43 Hydrothermal Plumes from LIPs

44 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

45 Two Styles of Mantle Convection

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

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