Volcanoes & Volcanic Activity By Philipp S., 3 rd hour.
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Transcript of Volcanoes & Volcanic Activity By Philipp S., 3 rd hour.
Volcanoes & Volcanic Volcanoes & Volcanic ActivityActivity
By Philipp S., 3By Philipp S., 3rdrd hour hour
Shield VolcanoShield Volcano
They are a large They are a large volcano which has volcano which has shallow-sloping sidesshallow-sloping sides
They have basaltic They have basaltic magma that is not magma that is not viscous -> so it flows viscous -> so it flows very farvery far
Shield volcanoes Shield volcanoes are not explosive are not explosive because of the because of the basaltic magmabasaltic magma
http://en.wikipedia.org/wiki/Shield_volcanohttp://en.wikipedia.org/wiki/Shield_volcano
http://www.alohablooms.com/img/snow012302/maunakea_snow_coconut_leaf.jpg
StratovolcanoStratovolcano Is composed of many Is composed of many
layers of hardened lava, layers of hardened lava, tephra, and volcanic ashtephra, and volcanic ash
Is a tall, conical volcanoIs a tall, conical volcano Has andesitic or rhyolitic Has andesitic or rhyolitic
magma which doesn’t magma which doesn’t flow good because it’s flow good because it’s very viscousvery viscous
They are very explosive They are very explosive because of the non-because of the non-viscous magmaviscous magma
http://en.wikipedia.org/wiki/Stratovolcanohttp://en.wikipedia.org/wiki/Stratovolcano
http://en.wikipedia.org/wiki/Image:Popocat%C3%A9petl_sunrise.jpg
Cinder ConeCinder Cone
Made from rock Made from rock fragments that fragments that accumulate around accumulate around and downwind from and downwind from volcanic ventvolcanic vent
They are steep, They are steep, conical hillsconical hills
They are located on They are located on the flanks of shield the flanks of shield volcanoes, volcanoes, stratovolcanoes and stratovolcanoes and calderascalderas
http://en.wikipedia.org/wiki/Paricutinhttp://en.wikipedia.org/wiki/Paricutin
http://en.wikipedia.org/wiki/Image:Paricutin.jpg
CalderaCaldera
Forms after a big Forms after a big eruption of a volcanoeruption of a volcano
The volcano collapses The volcano collapses because there is no because there is no more magma under it.more magma under it.
They can explode in They can explode in huge eruptions that huge eruptions that are 2500 times as big are 2500 times as big as the eruption of Mt. as the eruption of Mt. St. HelensSt. Helens
http://en.wikipedia.org/wiki/Caldera
http://en.wikipedia.org/wiki/Image:Santorini_Landsat.jpg
Lava DomeLava Dome
Forms in the crater Forms in the crater of a volcanoof a volcano
It is formed by a It is formed by a slow eruption of slow eruption of rhyolitic magmarhyolitic magma
Most Most stratovolcanoes stratovolcanoes have a lava dome in have a lava dome in their cratertheir crater
http://en.wikipedia.org/wiki/Lava_domehttp://en.wikipedia.org/wiki/Lava_dome
http://en.wikipedia.org/wiki/Image:MSH06_aerial_crater_from_north_high_angle_09-12-06.jpg
Flood BasaltFlood Basalt
They are results of They are results of gigantic volcano gigantic volcano eruptionseruptions
Have lava with low Have lava with low viscosity -> basalticviscosity -> basaltic
They can be from They can be from 200,000km200,000km2 2 to to 1,500,000km1,500,000km22
http://en.wikipedia.org/wiki/http://en.wikipedia.org/wiki/Flood_basalt#StructuresFlood_basalt#Structures
http://en.wikipedia.org/wiki/Image:3-Devils-grade-Moses-Coulee-Cattle-Feed-Lot-PB110016.JPG
Basaltic LavaBasaltic Lava
High temperature: High temperature: 1200°C1200°C
Silica-poor, low Silica-poor, low viscosity (flow very viscosity (flow very good), low gas contentgood), low gas content
The thin lava flows The thin lava flows form shields form shields
->Shieldvolcano->Shieldvolcano Is not explosive, it’s Is not explosive, it’s
flowingflowing
http://www.teara.govt.nz/EarthSeaAndSky/http://www.teara.govt.nz/EarthSeaAndSky/NaturalHazardsAndDisasters/NaturalHazardsAndDisasters/Volcanoes/1/ENZ-Resources/Standard/Volcanoes/1/ENZ-Resources/Standard/3/en3/en
http://www.earlham.edu/~yeakech/pics/basalt.jpg
Andesitic MagmaAndesitic Magma
Moderate temperature: Moderate temperature: 1000°C1000°C
Moderate silica content, Moderate silica content, moderate viscosity, moderate viscosity, moderate gas contentmoderate gas content
It’s flowing and It’s flowing and moderate explosivemoderate explosive
Forms thick lava flowsForms thick lava flows Mainly in Mainly in
StratovolcanoesStratovolcanoeshttp://www.teara.govt.nz/EarthSeaAndSky/http://www.teara.govt.nz/EarthSeaAndSky/
NaturalHazardsAndDisasters/Volcanoes/NaturalHazardsAndDisasters/Volcanoes/1/ENZ-Resources/Standard/3/en1/ENZ-Resources/Standard/3/en
http://www.ufrsd.net/staffwww/stefanl/Geology/volcano/pahoehoe.jpg
Rhyolitic MagmaRhyolitic Magma
Low temperature: 850°CLow temperature: 850°C Silica-rich, very high Silica-rich, very high
viscosity (doesn’t flow viscosity (doesn’t flow very good), high gas very good), high gas content ->very explosivecontent ->very explosive
Eruption product: Eruption product: pyroclastic flows, ash fall pyroclastic flows, ash fall
Mainly in calderasMainly in calderas
http://www.teara.govt.nz/EarthSeaAndSky/http://www.teara.govt.nz/EarthSeaAndSky/NaturalHazardsAndDisasters/Volcanoes/1/ENZ-NaturalHazardsAndDisasters/Volcanoes/1/ENZ-Resources/Standard/3/enResources/Standard/3/en
http://www.discoverourearth.org/student/volcanoes/images/st_helens_mosaic3.gif
Plinian EruptionPlinian Eruption
Is characterized by Is characterized by large gas blast large gas blast eruptions which are eruptions which are very loud very loud
Extends columns of Extends columns of smoke and ash high smoke and ash high into the stratosphere into the stratosphere
The ash deposits over The ash deposits over large areaslarge areas
Erutpions can last from Erutpions can last from one day to several one day to several monthsmonths
http://en.wikipedia.org/wiki/Plinian_eruptionhttp://en.wikipedia.org/wiki/Plinian_eruption
http://upload.wikimedia.org/wikipedia/commons/f/f4/Vesuvius1822scrope.jpg
Strombolian EruptionStrombolian Eruption
Eject lava bombs to Eject lava bombs to altitudes of tens to altitudes of tens to hundreds of metershundreds of meters
Is a low level Is a low level eruption but can last eruption but can last very longvery long
The lava flows are The lava flows are more viscous more viscous
-> andesitic-> andesitic
http://en.wikipedia.org/wiki/Strombolian_eruptionhttp://en.wikipedia.org/wiki/Strombolian_eruption
http://upload.wikimedia.org/wikipedia/commons/9/93/Stromboli_Eruption.jpg
Hawai’ian EruptionHawai’ian Eruption
Low level eruption, Low level eruption, with basaltic lavawith basaltic lava
The lava flows flow The lava flows flow very far because very far because basaltic lava has basaltic lava has low viscositylow viscosity
http://en.wikipedia.org/wiki/Hawaiian_eruptionhttp://en.wikipedia.org/wiki/Hawaiian_eruption
http://www.ldeo.columbia.edu/news/2005/images/eruption.jpg
Phreatic EruptionPhreatic Eruption
Occur when magma Occur when magma makes contact with makes contact with ground waterground water
The water The water evaporates nearly evaporates nearly instantaneous instantaneous
This causes a steam This causes a steam explosionexplosion
It typically include It typically include rock fragmentsrock fragments
http://en.wikipedia.org/wiki/Phreatic_eruptionhttp://en.wikipedia.org/wiki/Phreatic_eruption
http://upload.wikimedia.org/wikipedia/commons/8/8a/Phreatic.jpg
SillSill
Is a intrusion that Is a intrusion that intruded between intruded between older layers of older layers of sedimentary rock sedimentary rock
They can be from They can be from fractions of an inch fractions of an inch to hundreds of feet to hundreds of feet thick and up to thick and up to hundreds of miles hundreds of miles longlong
http://en.wikipedia.org/wiki/Sill_%28geology%29http://en.wikipedia.org/wiki/Sill_%28geology%29
http://z.about.com/d/geology/1/0/J/S/sill.jpg
BatholithBatholith
Forms from cooled Forms from cooled magma deep in the magma deep in the Earth’s crustEarth’s crust
When the When the surrounding rock surrounding rock erodes the batholith erodes the batholith stays because it is stays because it is made out of very made out of very hard rockhard rock
http://en.wikipedia.org/wiki/Batholithhttp://en.wikipedia.org/wiki/Batholith
http://whatonearth.olehnielsen.dk/img/batholith.jpg
DikeDike
It’s an intrusion that It’s an intrusion that cuts cross pre-cuts cross pre-existing or old existing or old bodies of rockbodies of rock
They sometimes They sometimes appear as swarmsappear as swarms
They are made They are made from either basaltic, from either basaltic, rhyolitic or granitic rhyolitic or granitic magma magma
http://en.wikipedia.org/wiki/Dike_http://en.wikipedia.org/wiki/Dike_%28geology%29%28geology%29
http://www.calvin.edu/academic/geology/pics/adirondacks/dike.jpg
StockStock
Have a surface Have a surface exposure of less exposure of less than 40 square than 40 square milesmiles
Is like a small Is like a small batholithbatholith
Most stocks are Most stocks are probably the tops of probably the tops of hidden batholithshidden batholiths
http://en.wikipedia.org/wiki/Stocks_http://en.wikipedia.org/wiki/Stocks_%28geology%29%28geology%29
http://www.geo.arizona.edu/tectonics/Ducea/projects/Huatulco%20batholith2.jpg
LaccolithLaccolith
Is between two layers Is between two layers of sedimentary rockof sedimentary rock
Looks like a dome or Looks like a dome or mushroom mushroom
Are formed by Are formed by viscous magma -> viscous magma -> andesitic or granitic andesitic or granitic magmamagma
It cools slowly down It cools slowly down and forms large and forms large crystalscrystals
http://en.wikipedia.org/wiki/Laccolithhttp://en.wikipedia.org/wiki/Laccolithhttp://mason.gmu.edu/~sharlan/adelmountainvolcanics_files/image014.jpg