UNDERSTANDING VOLCANOS

UNDERSTANDING VOLCANOSUNDERSTANDING VOLCANOS

Dr. Walter Hays, Global Alliance For Disaster Reduction

ESSENTIAL KNOWLEDGE FOR ESSENTIAL KNOWLEDGE FOR SOCIETAL SUSTAINABILITYSOCIETAL SUSTAINABILITY

A FRAMEWORK FOR A FRAMEWORK FOR UNDERSTANDING THE IMPACTS UNDERSTANDING THE IMPACTS OF VOLCANIC ERUPTIONS ON OF VOLCANIC ERUPTIONS ON

PEOPLE AND THEIR COMMUNITIESPEOPLE AND THEIR COMMUNITIES

GLOBAL DISTRIBUTION OF 1,500 GLOBAL DISTRIBUTION OF 1,500 ACTIVE VOLCANOESACTIVE VOLCANOES

ERUPTIONS OF MOUNT ERUPTIONS OF MOUNT MERAPI MERAPI

May 15, and June 6 - 8, 2006May 15, and June 6 - 8, 2006

LOCATION IN CENTRAL JAVALOCATION IN CENTRAL JAVA

MOUNT MERAPI RECEIVED CLOSE MOUNT MERAPI RECEIVED CLOSE ATTENTION ON APRIL 18ATTENTION ON APRIL 18

INDONESIA’S MOUNT MERAPI INDONESIA’S MOUNT MERAPI ERUPTED ON MAY 15, 2006ERUPTED ON MAY 15, 2006

Mount Merapi, a Mount Merapi, a stratovolcano, stratovolcano, emitted lava, emitted lava, debris, and a debris, and a pyroclastic flow pyroclastic flow (or cloud) on (or cloud) on May 15. May 15.

MAY 15, 2006 ERUPTIONMAY 15, 2006 ERUPTION

Hot ash Hot ash released.released.


Volcanic ash Volcanic ash turned turned everything everything whitewhite

MAY 15, 2006 ERUPTIONMAY 15, 2006 ERUPTION School children School children

wore masks to wore masks to counter adverse counter adverse health effects of health effects of breathing breathing volcanic ash.volcanic ash.


Volcanic Volcanic ash covered ash covered crops and crops and vegetationvegetation..


Volcanic ash Volcanic ash covered covered automobiles automobiles and affected and affected jet airline jet airline traffic.traffic.

MOUNT MERAPI ERUPTED AGAIN MOUNT MERAPI ERUPTED AGAIN ON JUNE 6-8, 2006ON JUNE 6-8, 2006

Mount Merapi Mount Merapi volcano emitted volcano emitted lava, debris, and lava, debris, and pyroclastic flows pyroclastic flows (superheated (superheated clouds of gas) on clouds of gas) on Tuesday, June 6 Tuesday, June 6 and Wednesday, and Wednesday, June 7. June 7.

EXPLOSIVENESS OF JUNE 8 EXPLOSIVENESS OF JUNE 8 ERUPTION SENT 15,000 FLEEINGERUPTION SENT 15,000 FLEEING

EVACUATIONEVACUATION

11,000 from 11,000 from three districts three districts evacuated to evacuated to schools and schools and otheren “safe otheren “safe haven” emer-haven” emer-gency shelters.gency shelters.

MANY CHOSE TO EVACUATEMANY CHOSE TO EVACUATE

Many citizens Many citizens chose to chose to evacuate.evacuate.

Evacuation was Evacuation was ordered.ordered.

Villagers Villagers remembered the remembered the 1994 disaster.1994 disaster.

MANY CHOOSE NOT TO MANY CHOOSE NOT TO EVACUATEEVACUATE

Many citizens Many citizens chose chose not to not to evacuateevacuate because because shelters are shelters are boring and they boring and they wanted to provide wanted to provide for livestock and for livestock and tend crops.tend crops.

ESSENTIAL KNOWLEDGE ESSENTIAL KNOWLEDGE ON VOLCANOESON VOLCANOES

Plate tectonics and Plate tectonics and volcanic activityvolcanic activity

Global distribution of volcanoes Global distribution of volcanoes Most volcanoes are located Most volcanoes are located within within or near ocean basinsor near ocean basins

Basaltic rocksBasaltic rocks: in oceanic and : in oceanic and continental settingscontinental settings

Granitic rocksGranitic rocks: in continental : in continental settingssettings

The nature of The nature of volcanic eruptionsvolcanic eruptions

Three Three physical characteristics of a magmaphysical characteristics of a magma control its viscosity, the physical property control its viscosity, the physical property that ultimately determines the that ultimately determines the “violence”“violence” or or explosivenessexplosiveness, of the eruption: , of the eruption:

Composition Composition TemperatureTemperatureDissolved gasesDissolved gases

The magma affects the severity The magma affects the severity of a volcanic eruptionsof a volcanic eruptions

In summaryIn summary–Basaltic Magmas = Basaltic Magmas = mild eruptionsmild eruptions–Rhyolitic or Andesitic Rhyolitic or Andesitic Magmas = Magmas = explosive explosive eruptionseruptions

The nature of volcanic eruptionsThe nature of volcanic eruptions ViscosityViscosity is a measure of a is a measure of a

material’s resistance to flowmaterial’s resistance to flow Factors affecting viscosityFactors affecting viscosity

TemperatureTemperature - Hotter - Hotter magmas are less viscousmagmas are less viscous

CompositionComposition - - Silica (SiOSilica (SiO22) ) contentcontent

The nature of volcanic eruptionsThe nature of volcanic eruptions–Higher silica contentHigher silica content = higher = higher viscosity (e.g., viscosity (e.g., felsic lava such felsic lava such as rhyolite)as rhyolite)–Lower silica contentLower silica content = lower = lower viscosity (e.g., viscosity (e.g., mafic lava such mafic lava such as basaltas basalt) )

The nature of volcanic eruptionsThe nature of volcanic eruptionsDissolved gasesDissolved gases–Gas content affects magma Gas content affects magma mobilitymobility–Gases Gases expandexpand within a magma as within a magma as it nears the Earth’s surface due it nears the Earth’s surface due to decreasing pressureto decreasing pressure–The The violence of an eruption is violence of an eruption is related to how easily gasesrelated to how easily gases escape escape from magmafrom magma

Materials extruded Materials extruded from a volcanofrom a volcano

Lava flowsLava flowsBasaltic lavas exhibit fluid behaviorBasaltic lavas exhibit fluid behaviorTypes of basaltic flowsTypes of basaltic flows–Pahoehoe lavaPahoehoe lava (resembles a twisted or (resembles a twisted or

ropey texture)ropey texture)–Aa lavaAa lava (rough, jagged blocky texture) (rough, jagged blocky texture)

Dissolved gasesDissolved gases1% - 6% by weight1% - 6% by weightMainly HMainly H22O and COO and CO22

Materials extruded Materials extruded from a volcano from a volcano

Pyroclastic materialsPyroclastic materials – “fire fragments” – “fire fragments”•Types of Types of pyroclastic debrispyroclastic debris–Ash and dustAsh and dust - fine, glassy - fine, glassy

fragmentsfragments–PumicePumice - porous rock from - porous rock from

“frothy” lava“frothy” lava–CindersCinders - pea-sized material - pea-sized material

Materials extruded Materials extruded from a volcano (continued) from a volcano (continued)

Pyroclastic materials – Pyroclastic materials – “fire fragments”“fire fragments”•Types of Types of pyroclastic debrispyroclastic debris–LapilliLapilli - - walnut-sized materialwalnut-sized material –Particles larger than lapilliParticles larger than lapilli

BlocksBlocks - - hardened or cooled hardened or cooled lavalava

Bombs - Bombs - ejected as hot lavaejected as hot lava

VolcanoesVolcanoes General featuresGeneral features

Opening at the summit of a volcanoOpening at the summit of a volcano–CraterCrater - - summit depression < 1 km summit depression < 1 km

diameterdiameter–CalderaCaldera - - summit depression > 1 km summit depression > 1 km

diameter produced by collapse following diameter produced by collapse following a massive eruptiona massive eruption

VentVent – surface opening connected to the – surface opening connected to the magma chambermagma chamber

Fumarole Fumarole – emit only gases and smoke– emit only gases and smoke

VolcanoesVolcanoes

Types of volcanoesTypes of volcanoesShield volcanoShield volcano–Broad, slightly domed-shapedBroad, slightly domed-shaped–Generally cover large areasGenerally cover large areas–Produced by mild eruptions of Produced by mild eruptions of large volumes of large volumes of basaltic lavabasaltic lava–Example: Mauna Loa on HawaiiExample: Mauna Loa on Hawaii

VolcanoesVolcanoes

Cinder coneCinder cone–Built from ejected lavaBuilt from ejected lava (mainly cinder-sized) (mainly cinder-sized) fragmentsfragments–Steep slope angleSteep slope angle–Small sizeSmall size–Frequently occur in groupsFrequently occur in groups

VolcanoesVolcanoes

Composite cone (stratovolcanoComposite cone (stratovolcano))–Most are located adjacent to Most are located adjacent to the Pacific Ocean the Pacific Ocean (e.g., (e.g., Fujiyama, Mt. St. Helens)Fujiyama, Mt. St. Helens)–Large, classic-shaped volcano Large, classic-shaped volcano ((1000’s of ft. high and several 1000’s of ft. high and several miles wide at base)miles wide at base)

Mt. St. Helens – prior Mt. St. Helens – prior to the 1980 eruptionto the 1980 eruption

Mt. St. Helens (after Mt. St. Helens (after the 1980 eruption)the 1980 eruption)

VolcanoesVolcanoes

Composite cone (stratovolcano) -Composite cone (stratovolcano) -continuedcontinued–Composed of interbedded lava Composed of interbedded lava flows and pyroclastic debrisflows and pyroclastic debris–Most violent type of activity Most violent type of activity (e.g., Mt. Vesuvius)(e.g., Mt. Vesuvius)

Volcanic HazardsVolcanic HazardsNuNuéée ardentee ardente – –A A Fiery pyroclastic flowFiery pyroclastic flow made of made of hot gases infused with ash and hot gases infused with ash and other debrisother debris

Also known as Also known as “glowing “glowing avalanches”avalanches”

Move down the slopes of a Move down the slopes of a volcano with volcano with velocities velocities approaching 200 km/hourapproaching 200 km/hour

Volcanic HazardsVolcanic HazardsLahar Lahar – – volcanic landslide or volcanic landslide or mudflowmudflow

Mixture of volcanic Mixture of volcanic debris and waterdebris and water

Move down slopes of Move down slopes of volcano and stream volcano and stream valleys with valleys with velocities of velocities of 30 to 60 miles/hour30 to 60 miles/hour

volcanic hazardsvolcanic hazards

Pyroclastic flowPyroclastic flowFelsicFelsic and and intermediateintermediate magmas magmasConsists of Consists of ash, pumice, and other ash, pumice, and other debrisdebris

Material ejected at Material ejected at high velocitieshigh velocitiesExample: Example: Yellowstone plateauYellowstone plateau

Other volcanic landformsOther volcanic landforms CalderaCaldera

Steep-walled depressions at the Steep-walled depressions at the summitsummit

Generally > 1 km in diameterGenerally > 1 km in diameterProduced by collapseProduced by collapseExample:Example: Crater Lake, Oregon Crater Lake, Oregon

Other volcanic landformsOther volcanic landforms Fissure eruptionsFissure eruptions and and lava plateauslava plateaus

Fluid basaltic lava extruded from Fluid basaltic lava extruded from crustal fractures called fissurescrustal fractures called fissures

Example: Example: Columbia River PlateauColumbia River Plateau Lava domesLava domes

Bulbous mass of congealed lavaBulbous mass of congealed lavaAssociated with explosive eruptionsAssociated with explosive eruptions of of

gas-rich magmagas-rich magma

Other volcanic landformsOther volcanic landforms

Volcanic pipesVolcanic pipes and and necksnecksPipesPipes - short conduits that - short conduits that connect a magma chamber to the connect a magma chamber to the surfacesurface

Volcanic necksVolcanic necks (e.g., Ship Rock, (e.g., Ship Rock, New Mexico) - resistant vents left New Mexico) - resistant vents left standing after erosion has standing after erosion has removed the volcanic coneremoved the volcanic cone

Shiprock, New MexicoShiprock, New Mexico

Intrusive igneous activityIntrusive igneous activity Most magma is emplaced at Most magma is emplaced at

depthdepth in the Earth in the EarthOnce cooled and solidified, it Once cooled and solidified, it is called a is called a plutonpluton

Intrusive igneous activityIntrusive igneous activity Nature of plutonsNature of plutons

ShapeShape - tabular (sheetlike) vs. - tabular (sheetlike) vs. massivemassive

Orientation with respect to Orientation with respect to the host (surrounding) rockthe host (surrounding) rock–ConcordantConcordant vs. vs. discordantdiscordant

Intrusive igneous activityIntrusive igneous activity Types of intrusive igneous featuresTypes of intrusive igneous features

DikeDike – a tabular, discordant – a tabular, discordant plutonpluton

SillSill – – a tabular, concordant a tabular, concordant pluton (e.g., Palisades Sill in pluton (e.g., Palisades Sill in New YorkNew York))

Intrusive igneous activityIntrusive igneous activity Types of intrusive igneous featuresTypes of intrusive igneous features

LacolithLacolith–Similar to a sillSimilar to a sill–Lens or mushroom-shaped massLens or mushroom-shaped mass–Arches overlying strata upwardArches overlying strata upward

Intrusive igneous activityIntrusive igneous activity Intrusive igneous features continuedIntrusive igneous features continued

BatholithBatholith–Largest intrusive bodyLargest intrusive body–Surface exposure > 100+ kmSurface exposure > 100+ km22

(smaller bodies are termed (smaller bodies are termed stocksstocks))–Frequently form the Frequently form the cores of cores of mountainsmountains

Plate tectonics and Plate tectonics and igneous activityigneous activity

Global distribution of igneous activity Global distribution of igneous activity Most volcanoes are located Most volcanoes are located within within or near ocean basinsor near ocean basins

Basaltic rocksBasaltic rocks: oceanic and : oceanic and continental settingscontinental settings

Granitic rocksGranitic rocks: continental settings: continental settings


Igneous activity at plate marginsIgneous activity at plate marginsSpreading centersSpreading centers–Greatest volume of volcanic Greatest volume of volcanic rock is produced along the rock is produced along the oceanic ridge systemoceanic ridge system


Igneous activity at plate marginsIgneous activity at plate marginsMechanics of spreadingMechanics of spreading

Decompression meltingDecompression melting of the of the mantle occurs as the lithosphere mantle occurs as the lithosphere is pulled apartis pulled apart

Large quantities of basaltic Large quantities of basaltic magma are producedmagma are produced

Plate tectonics and igneous activityPlate tectonics and igneous activity

Subduction zonesSubduction zones–Occur in conjunction with Occur in conjunction with deep deep

oceanic trenchesoceanic trenches–Location of partial meltingLocation of partial melting of of

descending plate and upper mantledescending plate and upper mantle–Rising magma can formRising magma can form either either

An island arcAn island arc if in the ocean if in the oceanA volcanic arcA volcanic arc if on a continental if on a continental

marginmargin


Subduction zones are associated Subduction zones are associated with the Pacific Ocean Basinwith the Pacific Ocean Basin

The region representing the The region representing the Pacific Rim is known as the Pacific Rim is known as the “Ring of Fire”“Ring of Fire”

Location of majority of Location of majority of world’s explosive volcanoes world’s explosive volcanoes

Plate tectonics and igneous activityPlate tectonics and igneous activity Intraplate volcanismIntraplate volcanism

Occurs Occurs withinwithin a tectonic plate a tectonic plateAssociated with Associated with mantle plumesmantle plumesLocalized volcanic regions in the overriding Localized volcanic regions in the overriding

plate are called a plate are called a hot spothot spot–Produces Produces basaltic magma sourcesbasaltic magma sources in in

oceanic crust oceanic crust (e.g., Hawaii and Iceland)(e.g., Hawaii and Iceland)–Produces granitic magma sources in Produces granitic magma sources in

continental crust continental crust (e.g., Yellowstone Park)(e.g., Yellowstone Park)

Volcanoes and climateVolcanoes and climate The basic premiseThe basic premise

Explosive eruptions emit Explosive eruptions emit huge huge quantities of gases and fine-quantities of gases and fine-grained debris grained debris

A portion of the A portion of the incoming solar incoming solar radiation is reflected and radiation is reflected and filtered outfiltered out

Volcanoes and climateVolcanoes and climate Past examples of volcanism Past examples of volcanism

affecting climateaffecting climateMount Tambora, Indonesia – Mount Tambora, Indonesia – 18151815

Krakatau, Indonesia – Krakatau, Indonesia – 18831883

Volcanoes Can Impact Regional Volcanoes Can Impact Regional And Global ClimateAnd Global Climate

Modern examplesModern examplesMount St. Helens, Washington - Mount St. Helens, Washington - 19801980

El ChichEl Chichóón, Mexico - n, Mexico - 19821982Mount Pinatubo, Philippines - Mount Pinatubo, Philippines - 19911991

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UNDERSTANDING VOLCANOS