105_05-volcanoes_part_3 - Pyroclastic flow Pyroclastic flow...

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Unformatted text preview: Pyroclastic flow Pyroclastic flow - Montserrat - Tar River Valley Mount St. Helens Mount St. Helens Eruption Eruption May 18, 1980 after 123 yrs of silence Pyroclastic Pyroclastic flow destroyed everything w/in 30 km Everything Everything w/in 12 km covered with thick ash Trees Trees up to 20 km broke like matchsticks Tephra Tephra up to 25 km altitude Death Death toll: 60 humans, 500 deer, 200 bears, 1500 elk, countless birds and small animals Mount St. Helens Phreatic* eruption cloud, Mt. St. Helens *phreatic - involving groundwater, converted explosively to steam by heat from magma 1 Mount St. Helens Mount St. Helens Summer 2000 Mount St. Helens Summer 2000 Lava dome, Mount St. Helens Do all Eruptions Build Up Volcanoes? Fissure Fissure Eruptions and Basalt Plateaus – Columbia River basalts flowed from fissures to cover large areas in WA and OR – Low viscosity, mafic lavas spread out and built up a basalt plateau 2 How BIG are volcanic eruptions? Eruptions Eruptions are ranked by the volcanic explosivity index or VEI – Ranges from 0 (unexplosive) to 8 (megacolossal) – Based on volume of material explosively ejected, height of eruption plume – Volume of lava, human and property damage are not considered – Duration is widely variable, from days to years VEI How BIG are volcanic eruptions? Plume height <100 m 100-1000 1001-5 km 3-15 km 10-25 km 10>25 km >25 km >25 km >25 km Volume 1,000s m3 10,000s m3 1,000,000s m3 10,000,000s m3 100,000,000 m3 1 km3 10s km3 100s km3 1,000s km3 Example Kilauea Stromboli Galeras Ruiz Galunggung St. Helens Krakatau Tambora Yellowstone NonNon-explosive Gentle Explosive Severe Cataclysm Paroxysmal Colossol SuperSuper-colossal MegaMega-colossal Is it Possible to Predict Eruptions? Volcano Volcano monitoring – Physical and chemical changes Tiltmeters, Tiltmeters, seismic activity, past history Changes Changes in magnetic and electrical fields Gas Gas emissions, groundwater level and temp Predicting eruptions Satellite temperature Tiltmeter Observe escape of steam Seismographs – While timely warnings have been issued in the past, volcanoes remain unpredictable and only a few are regularly monitored Distribution of Volcanoes 95% are at or near plate boundaries Pacific surrounded by 80% of all volcanoes Cascadia Range Volcanism 3 Cascadia Range Volcanism North American Plate Plate Tectonics, Volcanoes, and Plutons Intraplate Intraplate Volcanism – Occurs as a plate moves over a stationary ‘hot spot’ in the upper mantle Juan de Fuca Plate Extraterrestrial Volcanism Chapter 1 Chapter 2 Chapter 3 Chapter 4 Exam 1 - Intro to Geology – Plate Tectonics – Minerals – Igneous Rocks Chapter 5 – Volcanoes Olympus Mons Volcano, Mars Exam 1 Bring Scantron, Pencil, ID!! Exam 1 Bring Scantron, Pencil and ID!! Kristie Cornell GEOL 105 – Exam 1 2/11/10 TEST C 4 Exam 1 EXAM 1!! – Bring Scantron, Pencil and ID!! 1 6 0 5 9 2 8 4 3 Volcanism and Volcanoes Cajun Card # Chapter 5 5 ...
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This note was uploaded on 05/18/2011 for the course GEOL 105 taught by Professor Jack during the Spring '08 term at University of Louisiana at Lafayette.

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