Modul 12 - Volcanoes

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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



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Shi ld V l


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Shi ld V lShield Volcanoes


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HOT SPOT

Cinder Cone VolcanoesCinder Cone Volcanoes


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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



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HAWAIIAN-HAWAI



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STROMBOLIAN - ANAK KRAKATAU



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VULCANIAN DOME - MERAPI



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VULCANIAN - SURTSEYAN



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VULCANIAN - PAPANDAYAN

GAMALAMA



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PELEEAN - ST HELLENS



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PLINIAN PINATUBO



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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



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Pacific Ocean

Volcanism inVolcanism in

Mid Oceanic RidgeMid Oceanic Ridge



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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

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Modul 12 - Volcanoes