Tài liệu tham khảo bài giảng địa lý và hải dương học bằng tiếng anh chuyên đề về Các điểm nóng, luồng và tuyệt chủng hàng loạt | 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) Examples: 1. East African Rifts 2. Red Sea 3. Atlantic Ocean 4. Pacific Ocean 5. Mediterranean Sea 6. Himalayas, Tibet 1 2 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 barrier reef fringing 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? 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! Mantle convection - the driving force for plate tectonics What causes the warmer material to rise? Mantle Plumes 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 Which is not a hotspot? Iceland Hawaii Yellowstone 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
