Presentation Transcript
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
Slide 16: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