Review Sheet for GEOS 218 at UA
Review Sheet for GEOS 218 at UA
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Date Created: 02/06/15
Geos 218 Geological Disasters amp Society Sept 30 2008 Starting VOLCANOES First magmatism and plate tectonics Headline News Volcano Erupts in Chile Spews Ash 12 Miles Up Santiago Chile Associated Press May 6 2008 Chile39s Chaiten volcano spewed lava and blasted ash more than 12 miles 19 kilometers into the sky on Tuesday prompting a total evacuation of the provincial capital and other settlements httplnewsnationalgeographiccomnews200805080506APchilevolcahtm A er a 9000year slumber the volcano has been erupting since May 2 and shows no signs of stopping Government vulcanologist Luis Lara told reporters that the dangerous eruption could last for months Headline News Chile39s Chait n volcano Headline News Chile39s Chait n volcano httpMwwboston combigpicturelZOOBOGch aitenvolcan ostiactivehtm Magmatism and Volcanoes volcanoes amp plate tectonics L melting in the earth L magmas and volcanic rocks L eruptive styles L types of volcanoes L volcanic hazards Peer Review of Lecture Notes 1 Exchange notes with person sitting to your left Move to another seat if you need a partner Review partner s notes to identify how many of the main lecture points are recorded Write in the margins of your partner s notes points that were missed Discuss your review and any other suggestions with your partner mm Muhma m mu MM tLLun Popo Popocateptl Mexico City Ma 0 volcanoes of Mexico njuanv x Ensenad URI Fl STA YES v U r a n zun Ann muss u an ant knometem Kml am a O Mumsngy MGM E J Mazme Dwanuu cam sanLum h Tamplco 5 Guau 3 are o 5 MEXcomm 1 A A Q o y 395 A A I Wm USESCVO 2003 nasmap modm39edlrom m 2103 memes mm 5min and smart 15w Potentially Active Volcanoes of Western United States A Glue mull l l ll l39lSlmkane A Mount Rainier39 Elens A W A A MotInlAdamSl A MoumlloBd A Moumle erson A Send A Newberry Crater A Crater Lake til all l H am A Craters oilhe Moon Great Falls Ellllngs stars lA Vellowstone Caspel 39Edlclne Lake A Fucaiellu l l m I Wanna l i Rena l Salt Lake on Denver SaniaFe A Vulcanu active during A San Francisco FIEld past mun years Albuquerque A Othelpuienilallyacilve 7 ABandEra Field vulcamcaleas WW Hr r 7 El lEIEI ZDEI Kllumeiels 7 H V WEI miles THESEquot y Hamidquot quot Divergent and convergent plate boundaries plus hotspots Mostly Why are there volcanoes on Earth Background Observations gtSwaves pass thru the crust and mantle crust amp mantle are solid Except for the outer core Earth is mostly solid Are volcanoes fed by the outer core gtVolcanoes are found in very special places hotspots and active tectonic plate boundaries gtZones of melting magma generation within the Earth must be very distinct Why What causes melting in the earth 1 mantle upwelling a ka decompression melting 2 just add water aka flux melting camMan ums u39m nwmsu v mummy pmmmw umzammmv Iuvunuumnv vmsanwmm mamas nmmwm mnst Magma generation camngm mam Haws mvz aauumw 10 Magma generation uaDu c iid Fun r or any MANTLE W852 formed out of subduc ng plate lntmduction of water from dghydra ng oceanic crusl drops melting pm of Ocean crust quotJus r add waferquot Wafer induced mel ring of ho r man rle r ock Produces basal ric magma 11 mm mm mm Gamer w mm mpyugmzww ma a m N Why do magmas form why do rocks melt a u WM1mu391u39Hh ESquot HWM 394 m w mm mm m hrmquz mm mu rnvvmwm Mhhstuw m quot39m39 nwvw39nm aw un a1a n W m 12 Igneous Rocks Minerals and Elements a 0 Elements 9 69 Si 0 Minerals 69 quartz Rocks 69 granite Elements silicon oxygen Periodic Table aluminum oftheEIements mu m u we m wia in calcium iron magnesium potassium sodium 13 Minerals quartz Si O pyroxene Fe Mg Ca Si O Rocks TEXTURE big or small xtals Coarse39Grained FineGrained Intrusive Extrusive Plutonic Volcanic oak Igneous Rock Rock Texture 14 ROCKS COMPOSITION mafic or felsic MAFIC gt high in Mg Fe low in Si Examples basalt gabbro darker color often erupt at divergent boundaries and oceanic hotspots oceanic crust is basalt mafic ROCKS COMPOSITION mafic or felsic FELSIC gt low in Mg Fe high in Si Examples rhyolite granite lighter color often erupt at subduction zones continental hotspots T continental crust is felsic to intermediate 15 TEXTURE big or small xtals gabbro granite 5 U5 gt 0 ll 03 E o E 3 o E 3 2 Q 392 a O n E O 0 A Comparison Composition of Major Magma Types MAFIC Lower in Si Higher in Fe amp Mg Lower gas content More fluid FELSIC Higher in Si Lower in Fe amp Mg Higher gas content Much less fluid Rhon ite fels in M Fl C Andesilze Basalt intermediate mafia elements 16 Igneous Rocks amp Plate Tectonics Malor Zones of Igneous Activity lmemedme amp fdsic Subduchon Zones Hoispat Voicamc Arc 39 Easaiiic me39media e Feisic Spreading Camer magmas magmas magmas Basaln c magmas i Upweliing Di magmas irom mamie Peer Review of Lecture Notes Egtltchange notes with person sitting to your left now Move to another seat if you need a partner Review partner s notes to identify how many of the main lecture points are recorded Write in the margins of your partner s notes points that were missed Discuss your review and any other suggestions with your partner 17 Summary of key points most volcanoes at divergent and convergent plate boundaries some at hotspots melting in the earth mantle upwelling and adding fluids to hot rock 3 elements gt minerals gt rocks 4 igneous rocks texture composition mafic vs felsic 5 mafic is usually oceanic felsic is usually continental The 3 Vs of volcanism viscosity volatiles and volume 18 VISCOSITY VISCOSITY motor oil andesite mantle Iavagtw rhyolltelava rocks air canola i quot F9 h ID 4 10 104 108 1012 10 6 102 102quot basalt lava oise water corn Lb p lll basalt andesite rhyolite 19 Explosiveness of Eruptions a a less Vlscous more viscous Gas bubbles can t escape because magma is highly viscous Rapidly Start to form expanding bubbles fragment magma into rock and ash Magma rises and gas bubbles 20 water H10 carbon dioxide 00 sulfur dioxide 80 hydrogen sulfide HIS magmatic gas contents 05 to 15 this means HUGE volumes of gas VOLATILES F 39 2 undegassed magma is potentially explosive 21 Comparison of Volcanic Eruptions St Helens Vesuvius St Helens Tambora 4600 301 1900 90 AD 79 1500 1815 Krakatoa Mt Katmai St Helens 1883 1912 May181980 Cloud represents all airborne ash and pumice Volume 4 VEI of erupted Examples 02 tephra 10 2 o 5 000001 km3 39 E 1 ll 00001km3 0 Monolnyo Cralers E 2 pasl5000years 3 001 km3 0 O E 3 g 01km3 W 4 Mounl Si Helens me May 18 1900 3 5 1km3 g i Pinatubo1991 g 10km3 Tambora 1815 gt100 km3 Long Valley Caldera 760000 years ago 600 km3 Yellowslone Caldera 600000 years ago 1000 km3 22 Summary of key points most volcanoes at divergent and convergent plate boundaries some at hotspots melting in the earth mantle upwelling and adding fluids to hot rock elements gt minerals gt rocks igneous rocks texture composition mafic vs felsic mafic is usually oceanic felsic is usually continental viscosity more felsic is way more viscous volatiles undegassed magma gt more explosive volumes Mt St Helens 1 km3 Yellowstone 1000 km3 I mmmm c5 39 Z gt 39 Wampum o 2uus ncyclavadu Er a quotc 23
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