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