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Intraplate volcanoes (3) - 6 Interpalte volcanoes a Very...

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Intraplate volcanoes 1. Location of intraplate ocean island volcanoes a. Scattered around the globe b. Not related to surface tectonic structure c. Most erupt within a tectonic plate d. Form chains of islands 2. How do you melt rocks? a. Heat them (e.g.; ice in a glass) sometimes happens in the lower crust b. Add a contaminated (e.g., add salt to ice) subduction c. Decompress them (lower pressure) divergent margins 3. Mantle Plumes a. The mantle is convecting solid body b. Mantle plumes show little motion relative to each other suggesting and origin in the earth (core-mantle boundary?) c. Magma erupted from volcanoes is caused by melting of mantle rock during decompression (upwelling) of mantle plume 4. Model of earth’s tectonic & mantle processes a. Ocean crust created a spreading of ridges b. Ocean crust subducted at convergent margins c. Mantle plumes arise from deep interior to form intraplate volcanoes 5. Effusive eruptions – lava flows a. Character of flows change as flows continue b. Pahoehoe can be converted to a’a (and vice versa)
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Unformatted text preview: 6. Interpalte volcanoes a. Very large Volcanoes b. Basaltic composition c. This layered shields d. Effusive, long duration e. Rarely explosive f. Extensive flows 7. Nature of interpolate volcanoes: structure of hotspot volcanoes a. Elongated b. Rift zones define elongation c. Summit magma reservoirs connect to rift zones d. Cyclic eruptions (quakes, tilting) e. Summit or rift zone eruptions 8. Large igneous Provinces (flood basalts) a. Columbia river basalt i. Erupted between 17 and 6 million years ago ii. Up to 6000ft thick iii. Flowed as much as 600 km from vent iv. Total erupted volume ~175,000 km 3 v. St Helens ~km 3 and ongoing vi. Kilaeua eruption ~2 km 3 and ongoing b. Many LIPs are over 10 times bigger than the Columbia river basalt c. How are flood basalts emplaced? i. Early models: catastrophic floods of lava ii. Most recent ideas: inflation of basalt sheets 1. Effusion rate, topography, slope all contribute to the final morphology of the flow field 2....
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