GEOS 212 1st Edition Lecture 4 Outline of Last Lecture 1. History of spreading in South Atlantic, North Atlantic, Eastern Pacific, Labrador Sea, and Indian Ocean2. Rates of spreading: rate is distance / time, usually km/my or cm/yra. The edge of the continent is usually not sea level, but the edge of thecontinental shelf3. Pacific Plate also has chain of islands from hot spot = Hawaii!a. Connection between mantle plume, hot spot, island chainb. Rate of motion calculation: distance / time, usually km/my or cm/yr4. Subduction zones in continental and oceanic settings5. Plate tectonics is the most efficient way for the earth to lose heat … that’s the simple reason that plates move.6. Early idea was that conveyor-belt convection ‘drives’ plate, but it has problems7. Some people now believe that plates slide away from ridges and toward subduction zones8. World Tour of subduction zones Outline of Current Lecture Volcanoes: 1500 could erupt, ~20 erupting most of the timeOccur in four tectonic settings:o Spreading centerso Hot Spotso Subduction ZonesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Continents Pulling ApartTwo main types of volcanoes:o Shield Volcanoes:o On oceanic crusto Not steep sideso Basalt (high iron); very hoto Not explosiveo Not Hazardouso Lava flows (runny)Strato Volcanoes: o On continental crusto Steep sideso Andesite (lower iron), cooler, stifo Explosiveo Hazardouso Lava flows, ash/cinders, pyroclastic flowsDiagrams of Shield & Strato VolcanoesVideos of shield volcano eruptionso % of volcanoes below sea surfaceo Importance of Kilaueao Temperature of lava?o Key to forecasting eruptions?o Nature of magmao Nature of basalt (color, texture)Videos of stratovolcano eruptionso What else comes from volcanoes besides magma? o Pyroclastic flow made up of rock, ash, gaseso Nature of magmao Nature of andesite ash (color, texture)o How many potentially active volcanoes?o How many people live at risk from volcanoes?- Cascade volcanoes in Oregon & Washington- Eruption history of the Cascade volcanoes- Caldera eruptions- Currently active Volcanoes (http://www.geocodezip.com/v2_activeVolcanos.asp)Current
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