1

GEOS 432-4; Volcanic processes and landforms

Plate Tectonics and VolcanismPlate Tectonics and Volcanism

Mantle hot spotsMantle hot spots

OceanicOceanic

BasalticBasaltic

ContinentalContinental

RhyoliticRhyolitic, andesitic, or , andesitic, or

basalticbasaltic

Plate tectonics and VolcanismPlate tectonics and Volcanism

Plate marginsPlate margins

DivergentDivergent--basalticbasaltic

Subduction of oceanic Subduction of oceanic

plateplate--andesiteandesite

2

Large scale landformsLarge scale landforms

Submarine volcanoes

Large scale landformsLarge scale landforms

Basalt plateaus

Volcanic ProductsVolcanic Products

GasGas

LavaLava

TephraTephra

3

GasGas

VentsVents

Hot springs, geysers, fumaroles, solfatarasHot springs, geysers, fumaroles, solfataras

Solfatara, Iceland Hot springs

Geyser, ―Strokkur‖ at

Geysir, Iceland

4

1 2

3 4

Mud volcanoMud volcano

http://ngm.nationalgeographic.com/ngm/20http://ngm.nationalgeographic.com/ngm/20

0808--01/volcano01/volcano--culture/drowningculture/drowning--inin--

mud.htmlmud.html

5

Lake Nyos case historyLake Nyos case history http://perso.wanadoo.fr/mhalb/nyos/index.htmhttp://perso.wanadoo.fr/mhalb/nyos/index.htm

LavaLava

CompositionComposition

Silica content: 35% (basalt) Silica content: 35% (basalt) –– 75% (rhyolite, 75% (rhyolite,

obsidian)obsidian)

ViscosityViscosity

Related to compositionRelated to composition--higher silicahigher silica——more more

viscousviscous

Temp and volatile content also importantTemp and volatile content also important

Volatiles decrease viscosity but degas at surfaceVolatiles decrease viscosity but degas at surface

Basalt 1100Basalt 1100--1200 degrees C1200 degrees C

Lava flowsLava flows

Vesicles Aa lava

Pahoehoe lava Aa lava flow

AA flow, Iceland

6

Rhylolite/obsidian flow

Obsidian

Columnar jointingColumnar jointing

7

Pillow lavasPillow lavas

TephraTephra

AshAsh——sand size & sand size &

smallersmaller

LapilliLapilli——gravelgravel

Blocks (Cold) Bombs Blocks (Cold) Bombs

(warm)(warm)

Pumice, 1875 eruption of Askja, IcelandPumice, 1875 eruption of Askja, Iceland

1875 Snow exposed1875 Snow exposed

8

Pyroclastic eruptionsPyroclastic eruptions

Heimaey, Iceland, 1973

2010 Eruption: 2010 Eruption: EyjafyallajökullEyjafyallajökull

http://www.youtube.com/watch?v=f1ztg0wUqKY

Pyroclastic flow or surgePyroclastic flow or surge

High temperature, very fast, very destructive

9

Mt. Pelee, 1902Mt. Pelee, 1902

Town of St. Pierre, Carribean Island of Martinique 30,000 killed

Mt. St. Helens, 1980Mt. St. Helens, 1980

Lateral Blast

Debris flows, Mt. St. HelensDebris flows, Mt. St. Helens

10

Mt St. Helens

LaharsLahars

Mt. Rainier

Orting, Washington

Mt. ShastaMt. Shasta

11

ArmeroArmero, , NevadoNevado del Ruiz, 1985del Ruiz, 1985

23,000 people killed

Volcanic landformsVolcanic landforms

L

a

v

a

Lava flow Exogenous dome Shield volcano Shield volcano

Scoria cone

Scoria cone

Shield volcano

Scoria cone Scoria cone Scoria cone

Tuff ring

Composite (strato) volcano Endogenous dome Ruptured ED

Maars with tephra Maar with rampart

Explosion caldera

Collapse caldera

Gas maar Explosion crater

12

Lava flowsLava flows——fissure or central ventfissure or central vent

Fissures, Iceland

Young lava flow, Iceland

Iceland

Lava Cascade, Iceland Fissure, Craters of the Moon

13

Basalt flow Craters of the Moon Miocene basalt flows from fissures-

Columbia River Plateau

Exogenous domesExogenous domes

Spatter cone-Iceland Shield Volcano-Iceland

Mauna Loa from Kilauea

Mauna Loa, as seen from Kilauea

14

Pyroclastic cones, ringsPyroclastic cones, rings

Tuff ring, northern Iceland

Scoria coneScoria cone

Tuff coneTuff cone

15

Tuff Ring, Iceland

Lake Myvatn, IcelandLake Myvatn, Iceland

16

Endogenous domesEndogenous domes

Mt. St. Helens

Composite (strato) volcanoesComposite (strato) volcanoes

17

Mt. Fuji

Craters, calderasCraters, calderas

Maar, New Mexico Crater Lake

18

Halemaumau pit craterHalemaumau pit crater

Summit caldera, Askja Volcano, IcelandSummit caldera, Askja Volcano, Iceland

Santorini, GreeceSantorini, Greece

19

MiscellaneousMiscellaneous

Icelandic Table Mountain Icelandic Table Mountain-Tuya

Tuya, Iceland

Miscellaneous Miscellaneous con’tcon’t

Lava tube

Tumuli

Tree mold

Volcanic neck