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Module 12Module 12
VolcanoesVolcanoes
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The gods of volcanoes doing their taskThe gods of volcanoes doing their task
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VOLCANOESVOLCANOES
AA volcanovolcano is ais a ventvent oror fissurefissure in the Earthin the Earths crusts crust
through which molten magma, hot gases, andthrough which molten magma, hot gases, and
other fluids escape to the surface of the land or toother fluids escape to the surface of the land or to
the bottom of the seathe bottom of the sea
Volcanoes may be classified broadly into:Volcanoes may be classified broadly into:
Central TypesCentral Types: the products escape via a single: the products escape via a single
pipe (vent)pipe (vent)
Fissure TypesFissure Types: the products escape from a: the products escape from a
linear vent or cracklinear vent or crack
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Vent positionsVent positions
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Central EruptionCentral Eruption
Fissure EruptionFissure Eruption
Side EruptionSide Eruption
Vent positionsVent positions
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EarthEarthss GeothermGeotherm
GEOTHERMGEOTHERM: increase in: increase in
temperature with depth in thetemperature with depth in the
earthearth
GEOTHERMAL GRADIENTGEOTHERMAL GRADIENT isisthe rate of change of T withthe rate of change of T with
depthdepth
In upper 100 km, averageIn upper 100 km, averagegeothermal gradient = 30geothermal gradient = 3000CC
kmkm --11
Heat source is decay ofHeat source is decay ofradioactive elementsradioactive elements
This heat causes melting ofThis heat causes melting of
rocks to form Magmarocks to form Magma
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Composition of MagmaComposition of Magma
Variation in magma properties include:Variation in magma properties include:
SILICA CONTENTSILICA CONTENT
varies from 45% to 75%varies from 45% to 75%
VOLATILES (GAS CONTENT)VOLATILES (GAS CONTENT)
most common gases: Hmost common gases: H22O vapor,O vapor,
COCO22, SO, SO22, H, H22SS
TEMPERATURE OF ERUPTED MAGMATEMPERATURE OF ERUPTED MAGMA
varies from 1200varies from 120000C to about 800C to about 80000CC
Variation in magma properties affectVariation in magma properties affect VISCOSITYVISCOSITY ofof
the magmathe magma
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Viscosity of MagmaViscosity of Magma
VISCOSITYVISCOSITY refers to the thickness or fluidity of arefers to the thickness or fluidity of a
liquidliquid
Liquid with HIGH viscosity are very thick,Liquid with HIGH viscosity are very thick,
stickysticky
Liquid with LOW viscosity are very fluidLiquid with LOW viscosity are very fluid
Effect of various properties on magma viscosity:Effect of various properties on magma viscosity: TemperatureTemperature: HIGH temperature = LOW: HIGH temperature = LOW
viscosity (viscosity (i.e.i.e. very fluid)very fluid)
Silica ContentSilica Content: HIGH silica = HIGH viscosity: HIGH silica = HIGH viscosity Volatile ContentVolatile Content: HIGH volatiles = LOW: HIGH volatiles = LOW
viscosityviscosity
(However,(However, high gas contentshigh gas contents contribute tocontribute toexplosiveexplosive eruptions)eruptions)
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Types of VolcanoesTypes of Volcanoes
T f V l
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Types of VolcanoesTypes of Volcanoes
Shi ld V lShi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V lShi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V lShi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V lShi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V lShi ld V l
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Shield VolcanoesShield Volcanoes
Shi ld V lShield Volcanoes
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Shield VolcanoesShield Volcanoes
HOT SPOT
Cinder Cone VolcanoesCinder Cone Volcanoes
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Cinder Cone VolcanoesCinder Cone Volcanoes
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Cinder Cone VolcanoesCinder Cone Volcanoes
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Cinder Cone VolcanoesCinder Cone Volcanoes
StratoStrato VolcanoesVolcanoes
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StratoStrato VolcanoesVolcanoes
StratoStrato VolcanoesVolcanoes
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StratoStrato VolcanoesVolcanoes
StratoStrato VolcanoesVolcanoes
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StratoStrato VolcanoesVolcanoes
StratoStrato VolcanoesVolcanoes
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StratoStrato VolcanoesVolcanoes
StratoStrato VolcanoesVolcanoes
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StratoStrato VolcanoesVolcanoes
StratoStrato VolcanoesVolcanoes
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Strato Volcanoes
Lava Dome VolcanoesLava Dome Volcanoes
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Lava Dome VolcanoesLava Dome Volcanoes
Dome VolcanoesDome Volcanoes
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Caldera VolcanoesCaldera Volcanoes
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Ca de a o ca oes
Caldera VolcanoesCaldera Volcanoes
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The formation ofThe formation of
CalderaCaldera
Eruption TypesEruption Types
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y
Eruption TypesEruption Types
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HAWAIIAN-HAWAI
Eruption TypesEruption Types
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STROMBOLIAN - ANAK KRAKATAU
Eruption TypesEruption Types
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VULCANIAN DOME - MERAPI
Eruption TypesEruption Types
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VULCANIAN - SURTSEYAN
Eruption TypesEruption Types
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VULCANIAN - PAPANDAYAN
GAMALAMA
Eruption TypesEruption Types
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PELEEAN - ST HELLENS
Eruption TypesEruption Types
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PLINIAN PINATUBO
Eruption TypesEruption Types
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PLINIAN - TAMBORA
Global Distribution of VolcanoesGlobal Distribution of Volcanoes
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Distribution of VolcanoesDistribution of Volcanoes
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MostMost subduction zones are in thesubduction zones are in the Ring of FireRing of Fire (so(so--calledcalled
because of volcanism of the Pacificbecause of volcanism of the Pacif ic))
from:http://www
.geo.lsa.umich.e
du/~crlb/COURSES/270
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Volcanism & Plate TectonicsVolcanism & Plate Tectonics
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Volcanism in continentalVolcanism in continental
Volcanism in islands arcVolcanism in islands arc
Volcanism & Plate TectonicsVolcanism & Plate Tectonics
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Pacific Ocean
Volcanism inVolcanism in
Mid Oceanic RidgeMid Oceanic Ridge
Volcanism & Plate TectonicsVolcanism & Plate Tectonics
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Hot Spot VolcanismHot Spot Volcanism
Classification of Volcanic EnvironmentClassification of Volcanic Environment
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Types and Zones of VolcanismTypes and Zones of Volcanism
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Finally . . .Finally . . .Rest in PeaceRest in Peace
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Rest in PeaceRest in Peace
VOLCANIC NECK
COLUMNAR JOINT