Volcanoes

Volcanoes : 

Volcanoes Chapter 7

Slide 3: 

Any activity that involves movement of magma toward or onto the surface of the Earth is volcanism Most magma formed at plate boundaries

Slide 4: 

As the plate subducts, the friction melts rock, as the crust enters the asthenosphere, it melts Magma that reaches the surface is lava, the opening is called a vent, volcanic material built up around the vent is a volcano

Slide 6: 

Types of Lava Mafic-Magnesium and iron, Dark Oceanic crust Felsic Lava more silica, light, continental crust

Mafic Lava Types : 

Mafic Lava Types Hawaii is where lava was first described, Pahoehoe-rope like Lava flows are thin compared to aa

Slide 9: 

Aa- sharp and broken Aa flows are thicker

Slide 11: 

Felsic eruptions tend to be explosive The silica in the lava makes it more viscous (thicker, like syrup) The thick lava builds up more pressure, leading to explosive eruptions

Slide 12: 

Mafic eruptions are slow and gradual The lava is thinner and pressure doesn't build up

Slide 13: 

Prediction of eruptions Most volcanoes have a combination of mafic and felsic magma making prediction of eruptions a tricky business

Slide 14: 

Change in composition of gasses from vents Bulges along slope of volcano Earthquakes

Tephra : 

Tephra Tephra, of pyroclastic material is organized by size

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Fragments -Sorted by size Felsic explode throwing tephra, pyroclastic material Dust Ash Lapilli Bombs Blocks House size

Cones : 

Cones Shield cones, mafic lava flows,broad and gentle

Cinder cones : 

Cinder cones Cinder cones, solid particles ejected from the volcano, steep

Composite : 

Composite Composite, lava and particles, broad and steep, stratovolcano, mountains

Slide 23: 

Craters, funnel shaped pit at the top of volcanic vents

Slide 24: 

Calderas basin shaped depression left after a major eruption

Hot spots : 

Hot spots Hot areas in Earth’s layers, cause volcanic activity on surface Hawaii, Jackson

Slide 27: 

Map of Global Hotspots

Problems With Hotspots : 

Problems With Hotspots Ages of Hawaiian volcanoes do not support model

Extraterrestrial Volcanism : 

Extraterrestrial Volcanism Moon, has evidence of volcanoes Mars, Olympus Mons, active? Ice volcanoes on Europa

Attributions : 

Attributions Pahoehoe and aa lava http://volcano.und.edu/vwdocs/vwlessons/lava.html Composite, cinder and shield volcanoes http://pubs.usgs.gov/gip/volc/types.html Caldera http://volcanoes.usgs.gov/Products/Pglossary/caldera_more.html Crater http://www.bergadventures.com/trips/ecuador_itin.html Volcanic structure geobytesgcse.blogspot.com/2007_01_01_archive.html Hot Spot http://pubs.usgs.gov/gip/dynamic/hotspots.html Hawaiian Hot Spot http://pubs.usgs.gov/gip/dynamic/Hawaiian.html Hot Spot Map http://pubs.usgs.gov/gip/dynamic/world_map.html