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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.

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Presentation on theme: "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."— Presentation transcript:

1 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?

2 Plate Tectonics - Distribution of Volcanic and Earthquake Activity

3 The Earth’s surface is broken into plates

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

5

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 barrier reef fringing reef

18 Pacific Hotspot Volcanic Chains

19 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?

20 Indian 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

21 JOIDES Resolution drillship

22 Reunion hotspot track, central Indian Ocean

23

24 “flood” basalts in western India >300 lava flows, each 1000 km 3

25 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

26 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?

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

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

38 Degassing Magma Gases include CO 2, SO 2, Cl, F that make “acid rain” Shuts down photosynthesis Gases include CO 2, SO 2, Cl, F that make “acid rain” Shuts down photosynthesis

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

40

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


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