VolcanoesVolcanoes

Volcanology: The study of volcanoesVulcanologists: scientists who study volcanoes

Anatomy of a VolcanoAnatomy of a Volcano

Central vent: where Central vent: where major eruption occursmajor eruption occurs

Flank vent: secondary Flank vent: secondary ventvent

Magma chamber: Magma chamber: where magma stays where magma stays until pressure forces it until pressure forces it up the ventup the vent

Fumarole: flank vent Fumarole: flank vent that releases gas onlythat releases gas only

A. Magma and LavaA. Magma and Lava

VolcanismVolcanism: : any activity that any activity that includes the includes the movement of movement of magma towards magma towards or on the or on the Earth's surfaceEarth's surface

MagmaMagma

MagmaMagma: : liquid liquid rockrock - volcanic rock - volcanic rock found below the found below the Earth's surface; solid Earth's surface; solid rock can become rock can become magma when liquid magma when liquid (water) is added (water) is added (subduction zones)(subduction zones)

Lava: magma that erupts onto the Earth's surface

Magma can flow onto Earth's surface through an opening - vent - or crack - fissure

A volcano is any structure formed on Earth's surface by the vent and volcanic material that builds up around it

B. Major Volcano ZonesB. Major Volcano Zones 1. 1. Subduction zonesSubduction zones – –

a. oceanic lithosphere melts a. oceanic lithosphere melts as it plunges beneath the as it plunges beneath the continental plate, water added continental plate, water added to mantle material creates to mantle material creates magma ex. Ring of Firemagma ex. Ring of Fire

b. ocean trenches where b. ocean trenches where oceanic subducts under oceanic subducts under oceanic creates volcanic oceanic creates volcanic islands arcsislands arcsex. Aleutian Islands, AK, ex. Aleutian Islands, AK, JapanJapan

2. 2. Mid-ocean Mid-ocean ridgesridges magma flows up magma flows up through rift zone, through rift zone, can form can form underwater underwater volcanoesvolcanoes

ex. Iceland - MOR ex. Iceland - MOR above sea-level; above sea-level; contains many contains many fissuresfissures

3. 3. Hot spotsHot spots - in - in the middle of a plate is the middle of a plate is a spot where magma a spot where magma flows upward; plate flows upward; plate moves over the hot moves over the hot spot and form a spot and form a volcano; volcano is volcano; volcano is carried away by plate carried away by plate and become extinctand become extinctex. Hawaiian Islandsex. Hawaiian Islands

A new Hawaiian island A new Hawaiian island forming underwater - forming underwater - LoihiLoihi

C. Types of LavaC. Types of Lava The violence of The violence of

an eruption an eruption depends ondepends on: : type of magma type of magma

(minerals)(minerals) temperature of temperature of

the magmathe magma The amount of The amount of

dissolved dissolved gasesgases

ViscosityViscosity viscosity viscosity - -

resistance to flowresistance to flow

More viscous - More viscous - flows slowlyflows slowly

Less viscous - Less viscous - flows quicklyflows quickly

Mafic LavaMafic Lava Dark colored Dark colored Contains magnesium Contains magnesium

and ironand iron Makes up Makes up oceanic oceanic

crustcrust Is hot and thin, less Is hot and thin, less

viscous - flows viscous - flows quickly - gases quickly - gases escape easily - escape easily - "quiet flow" "quiet flow"

ex. Hawaiian ex. Hawaiian volcanoesvolcanoes

PahoehoePahoehoe If mafic lava If mafic lava

cools slowly: cools slowly: forms wrinkly forms wrinkly crust - crust - pahoehoe pahoehoe - - Hawaiian for Hawaiian for "ropy""ropy"

AaAa if it cools if it cools

quickly: it quickly: it forms rough, forms rough, jagged chunks jagged chunks - - aaaa

Lava TubesLava Tubes If outer edges If outer edges

cool quickly cool quickly and inner lava and inner lava still flows: still flows: creates tunnel creates tunnel called called lava lava tubestubes

Pillow LavaPillow Lava Lava flowing Lava flowing

out of fissures out of fissures on ocean floor: on ocean floor: cools quickly & cools quickly & forms rounded forms rounded

pillow pillow lavalava

Felsic LavaFelsic Lava Is light coloredIs light colored

Contains silicaContains silica

Makes up Makes up continental continental crustcrust

Is cool and thick, more Is cool and thick, more viscous - lots of trapped viscous - lots of trapped gases - explosive!gases - explosive!

ex. continental volcanoes ex. continental volcanoes - Mt. St. Helens- Mt. St. Helens

D. Pyroclastic materialD. Pyroclastic material These are rock These are rock

fragments sent fragments sent into the air from into the air from explosive felsic explosive felsic lava eruptionslava eruptions

They are They are described by sizedescribed by size

Volcanic Dust and AshVolcanic Dust and Ash Volcanic dustVolcanic dust < <

0.25 mm in 0.25 mm in diameterdiameter

Volcanic ashVolcanic ash > > 0.25 - 2 mm0.25 - 2 mm

These may travel These may travel far from the far from the eruption!!eruption!!

Lapilli, Bombs and BlocksLapilli, Bombs and Blocks LapilliLapilli "little stones“ "little stones“

2 - 64 mm; they fall 2 - 64 mm; they fall near the ventnear the vent

Volcanic bombsVolcanic bombs - -clumps of lava sent clumps of lava sent spinning thru the air spinning thru the air

Volcanic blocksVolcanic blocks - - large rocks blasted large rocks blasted from fissure; can be from fissure; can be house-sizehouse-size

Pyroclastic flowPyroclastic flow The most deadly aspect to volcanic The most deadly aspect to volcanic

eruptionseruptions Combination of hot, toxic gases coming Combination of hot, toxic gases coming

from vents, up to 1000 C, and 750 km/hrfrom vents, up to 1000 C, and 750 km/hr More dense than air, so rolls into villages More dense than air, so rolls into villages

killing victims quickly (e.g. Pompeii) killing victims quickly (e.g. Pompeii) Video: Video: http://videos.howstuffworks.com/discovery/7153-volcanoes-pyroclastic-flow-video.htm http://videos.howstuffworks.com/discovery/7153-volcanoes-pyroclastic-flow-video.htm

E. Volcano TypesE. Volcano Typeshow do volcanoes form? how do volcanoes form? http://videos.howstuffworks.com/discovery/27683-assignment-discovery-formation-of-volcanoes-http://videos.howstuffworks.com/discovery/27683-assignment-discovery-formation-of-volcanoes-video.htm video.htm

1. 1. ShieldShield Volcanoes Volcanoes Form: when hot, Form: when hot,

mafic lava builds up mafic lava builds up around the vent - around the vent - form form conescones

Have wide, broad Have wide, broad bases and gently bases and gently sloping sides, sloping sides, medium heightmedium height

ex. Hawaiian Islandsex. Hawaiian Islands

2. 2. CinderCinder Cone Volcanoes Cone Volcanoes Very steep sloped Very steep sloped

sides, short (few sides, short (few hundred meters)hundred meters)

Formed from layers of Formed from layers of ash and other ash and other explosive pyroclastic explosive pyroclastic materialsmaterials

ex. Sunset Crater, AZex. Sunset Crater, AZ

3. 3. CompositeComposite Volcanoes, or Volcanoes, or StratovoclanoesStratovoclanoes

Composite means a Composite means a mix of unlike things, mix of unlike things, “strato-” means layer“strato-” means layer

Formed from Formed from alternating layers of alternating layers of lava and ashlava and ash

ex. Mt. Fuji, Mount ex. Mt. Fuji, Mount Hood, Mt. St. HelensHood, Mt. St. Helens

CraterCrater A pit at top of volcano, A pit at top of volcano,

formed when material formed when material is blown outis blown out

Usually widens due to Usually widens due to weathering and erosionweathering and erosion

Often a smaller cone Often a smaller cone may form inside crater may form inside crater

When filled with water When filled with water = a = a crater lake - crater lake - Crater Lake National Crater Lake National Park, OregonPark, Oregon

CalderaCaldera A large, basin A large, basin

shaped depression shaped depression formed from a craterformed from a crater

If magma chamber is If magma chamber is empty, the crater empty, the crater collapses - forms collapses - forms calderacaldera

Also formed from Also formed from huge eruptions huge eruptions

ex. Krakatauex. Krakatau

F. Predicting Volcanic Eruptions

Scientists use the following to predict EQs:

1. seismographs monitor for small EQs from growing pressure, that often precede eruptions

2. slight bulging of surface from magma pushing out

3. change in ground tilt

4. gases4. gases

5. history of 5. history of previous eruptionsprevious eruptions

Very few volcanoes Very few volcanoes have a lengthy have a lengthy history to study; history to study; constant constant monitoring is monitoring is requiredrequired

G. Extraterrestrial G. Extraterrestrial VolcanoesVolcanoes

Moon - Moon - was was once volcanically once volcanically active - evidence active - evidence of lava flowsof lava flows

Craters - a result Craters - a result of bombardment of bombardment by meteorites)by meteorites)

MarsMars - many volcanoes - many volcanoes and volcanic featuresand volcanic features

Olympic MonsOlympic Mons - shield - shield volcano - 28 km above volcano - 28 km above surface, base = 600 km; surface, base = 600 km; probably stayed on lava probably stayed on lava source for millions years source for millions years (no plate tectonics) (no plate tectonics)

Still active volcanoes on Still active volcanoes on Mars?? Not sure, but it is Mars?? Not sure, but it is seismically activeseismically active

IoIo Moon of JupiterMoon of Jupiter Many active volcanoes Many active volcanoes

- more eruptions; more - more eruptions; more material ejected than material ejected than on Earth each month; on Earth each month; probably sulfuric lava probably sulfuric lava

Spectacular eruptions - Spectacular eruptions - umbrella-shaped umbrella-shaped plumes hundreds km plumes hundreds km highhigh

Vulcanism probably Vulcanism probably caused by frictioncaused by friction

Importance of VolcanoesImportance of Volcanoes all original rocks on Earth's all original rocks on Earth's

crust were formed from crust were formed from cooled magma and/or lavacooled magma and/or lava

water vapor from volcanoes water vapor from volcanoes early in Earth's history may early in Earth's history may have formed oceanshave formed oceans

gases from early eruptions gases from early eruptions formed the atmosphereformed the atmosphere

volcanism adds new crust volcanism adds new crust and reshapes planet each and reshapes planet each yearyear

SupervolcanoesSupervolcanoes What are they?What are they?http://6.cn/watch/3812360.html http://6.cn/watch/3812360.html Several on youtube.comSeveral on youtube.com

ex: under Yellowstone National Parkex: under Yellowstone National Parkhttp://dsc.discovery.com/convergence/supervolcano/supervolcano.html http://dsc.discovery.com/convergence/supervolcano/supervolcano.html

Tsunami and landslidesTsunami and landslides Alaska: Alaska: http://geology.com/records/biggest-tsunami.shtml http://geology.com/records/biggest-tsunami.shtml

Volcano driven: East coast US Volcano driven: East coast US (when ?) (when ?) http://www.history.com/videos/mega-disasters-east-coast-tsunami#mega-disasters-http://www.history.com/videos/mega-disasters-east-coast-tsunami#mega-disasters-east-coast-tsunami east-coast-tsunami

10 ways the Earth will end: 10 ways the Earth will end: