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Igneous Structures and Field Relations-CH4

Image source hamblin and christiansen 2001 10

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Unformatted text preview: nsen (2001) 10 Landforms - central vent eruptions b) Composite Volcano (stratovolcano) Illustrative cross section of a stratovolcano image source: Winter (2010) Image source: J.D. Griggs, January 10, 1985 image source: Hamblin and Christiansen (2001) Mt. Rainier Composite cones are primarily composed of more Si-rich magmas (andesites to rhyolites). intermediate to high silica 11 Landforms - central vent eruptions c) Cinder Cone or scoria cone Video clip: http://www.swisseduc.ch/str omboli/volcano/video/index -en.html loose collection of airborne ash, lapilli, and blocks falling around central vent, generally at angle of Cinder cones in summit basin of Haleakala, HI Image source: virtual.yosemite.cc.ca.us/ghayes /Maui.htm repose. Undergo rapid erosion Cross sectional structure and morphology of small explosive volcanic landforms with approximate scales. image source: Winter (2010) 12 4 8/27/2012 Landforms - central vent eruptions d) spatter cone - clots of magma ejected from central vent: fluid, degrassing note symmetry, size of central vent, angles of repose Spatter cone in Galapagos Islands. Spatter commonly sticks together, or agglutinates, when it lands and is buried by later spatter. result of magma interaction with water image source: Barb Dutrow, LSU image source: Winter (2010) 13 Landforms - central vent eruptions c) maar - Low cone resulting from explosive interaction of magma with groundwater. Large central Left: Maar is ~300 m in diameter. Eruption column generated by phreatic and magmatic explosions rises from larger east maar. vent Below: Aerial view toward N of Ukinrek Maars, Alaska. Water partially fills eastern maar and completely covers lava dome that was erupted in 100-m deep crater during 10-day eruption in 1977. image source: http://volcanoes.usgs.gov/Products/Pglossary/maar.html 14 Landforms - central vent eruptions c) tuff cone or tuff ring - cone of pyroclastic material that dips inwards and outward at roughly the same a that dips inward and outward at roughly same angle Below: Tuff cone di Nisida (Campi Flegrei, Italy) Above: Tuff rings (Saudi Arabia) Tuff ring - Diamond Head, Hawaii image source: Winter (2010) Image source: http://www.ov.ingv.it/volcanolo gy/vulcanismo/tuff-conesrings.htm 15 5 8/27/2012...
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