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Classroom presentations to accompany Understanding Earth , 3rd edition. prepared by Peter Copeland and William Dupré University of Houston. Chapter 5 Volcanism. Volcanoes. Plumbing System of a Volcano. Fig. 5.1. May 1990 Eruption of Kilauea, Hawaii. James Cachero/Sygma.

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Classroom presentations to accompany Understanding Earth, 3rd edition

prepared by

Peter Copeland and William Dupré

University of Houston

Chapter 5

Volcanism


Volcanoes


Plumbing System of a Volcano

Fig. 5.1


May 1990 Eruption of Kilauea, Hawaii

James Cachero/Sygma


Major difference between plutonic

and volcanic rocks is texture, a

reflection of cooling rate.

Volcanic rocks


Nonvolatile material

Material ejected from volcanoes

  • Lava: magma that has flowed on the surface of the Earth.

  • Tephra: fragments that solidified in the air during eruption.


aa

pahoehoe

Types of Lava


Aa Lava

Pahoehoe

Lava

Fig. 5.3

Kim Heacox/DRX


Columbia Plateau Flow Basalts

Fig. 5.2

Martin G. Miller


Pyroclastic flow

Air-fall

Mudflow (lahar)

Tephra


Mixture of hot gases, ash, and rocks

forming a super-heated and dense

current capable of moving 150 km/hr.

Pyroclasticflow (nueé ardente)


Pyroclastic Flow from the 1998 Eruption on Montserrat

R.S.J. Sparks


Escaping a Pyroclastic Flow at Mount Unzen, Japan, 1991

Fig. 5.9

AP/Wide World Photos


Volcanic Bomb

Fig. 5.7

Science Source/Photo Researchers


Volcanic Breccia

Fig. 5.8

Doug Sokell/Visuals Unlimited


Pillow basalt

Phreatic explosions

Submarine eruptions


Pillow Lava

Fig. 5.4

Woods Hole Oceanographic Institute


Phreatic

Explosion

in the

Pacific

Fig. 5.18

Maritime Safety Agency, Japan


Vesicular Basalt

Fig. 5.5

Glen Oliver/Visuals Unlimited


Pyroclasic Eruption at Arenal Volcano, Costa Rica

Fig. 5.6

Gregory G. Dimijian/Photo Researchers


Shield volcanoes

Stratovolcanoes (composite)

Domes and cones

Fissure eruptions (flood basalts)

Submarine eruptions

Eruptive styles and landforms


Low-viscosity lava flows

Low-silica magma — mafic

Basalt

Pahoehoe

Aa

Gently sloping flanks — between 2 and 10 degrees

Tend to be very large

Spatter cone — minor feature

Shield volcanoes


Shield Volcano

Fig. 5.10


Olympus Mons

Shield Volcano

NASA, Viking Orbiter 1


Formed of pyroclastics only

Steep sides — ~30 degrees

Relatively small

Short duration of activity

Cinder cones


Cinder Cone

Fig. 5.12


Cerro Negro Cinder Cone, near Managua, Nicaragua in 1968

Fig. 5.13

Mark Hurd Aerial Surveys


Forms above a volcanic vent

Viscous lava — usually silica-rich (or cooler magma)

Associated with violent eruptions

Volcanic domes


Fig. 5.11


Inyo Obsidian Domes-California

P. L. Kresan


Lava

Dome

Fig.

5.11

Lyn Topinka/USGS


Alternating pyroclastic layers and lava flows

Slopes intermediate in steepness

Intermittent eruptions over long time span

Mostly andesite

Distribution

Circum-Pacific Belt (“Ring of Fire”)

Mediterranean Belt

Composite volcano


Composite Volcano

Fig. 5.14


Mt Fujiyama, Japan

Fig. 5.15

Raga/The Stock Market


Before May, 1980

Emil Muench/Photo Researchers


After May, 1980

David Weintraub/Photo Researchers


Depression at top of volcano produced during an eruption

May have younger domes within it

Caldera


Fig. 5.16


Crater Lake, Oregon

Fig. 5.17

Greg Vaughn/Tom Stack


Shiprock, New Mexico

an exposed volcanic pipe (diatreme)

Fig. 5.19

Fred Padula


When low-viscosity lava is

issued from cracks in the Earth

tens of kilometers long.

Fissure eruptions


1971 Fissure Eruption, Kilauea, Hawaii


Fissure Eruptions Form Lava Plateaus

Fig. 5.20


Laki fissure (Iceland) erupted in 1783 extruding the largest lava flow in human history.

Fig. 5.21

Tony Waltham


Mafic lava — solidifies to basalt

Fissure flows

Plateau basalts

Columnar structure or jointing

Lava floods


Fig. 5.22


Columbia Plateau Flow Basalts

Fig. 5.2

Martin G. Miller


Welded Tuff: California

Fig. 5.23

1 foot

Gerals and Buff Corsi/Visuals Unlimited


Ash-flow Sheets Draping Topography, Japan

Fig. 5.24

S. Aramaki


Caution: Volcanologist at Work

Fig. 5.25

Maurice Krafft/Photo Researchers


A mixture of water and pyroclastic

material in a concrete-like slurry

capable of moving up to 100

km/hour!

Volcanic Mudflow (lahar):


23,000 killed in 1985 by volcanic mudflows, Nevada del Ruiz

Barbara and Robert Decker


Volatile material

Other material ejected from volcanoes

  • Steam (H2O)

  • Carbon dioxide (CO2 )

  • Hydrogen sulfide (H2S)

  • Many other constituents


Sulfur-encrusted fumerole:

Galapagos Islands

Fig. 5.26

Christian Grzimek/Photo Researchers


Stokkur geyser in Iceland

Fig. 5.27

Simon Fraser/Photo Researchers


Convergent plate boundaries

Divergent plate boundaries

Within plate “hotspots”

Tectonic setting of volcanoes


The World’s Active Volcanoes

Fig. 5.28


Cross Section of the East Pacific Rise

Fig. 5.29


Volcanism Associated with Plate Tectonics

Fig. 5.30


Growth of Hawaii

Geothermal energy

Effect on climate

Volcanic catastrophes

Mt. St. Helens

Vesuvius

Krakatoa

Mt. Pelée

Montserrat

Effects of volcanoes on humans


Lava Flows: e.g. Hawaii, 1998

Gas: e.g. Lake Nyos (Cameroon), 1984

1700 people killed

Ash fall: e.g. Mt. Pinatubo, 1991

Pyroclastic flows: e.g. Mt. Pelee, 1902

28,000 killed

Lahars (mudflows): e.g. Nevado del Ruiz, 1985

23,000 killed

Tsunami: e.g. Krakatoa, 1883

36,417 killed

Types of Volcanic Hazards


San Juan, Mexico, Buried by Paricutin Lava Flows

E. Tad Nichols


Scientists Investigate Mt. Pinatubo’s Caldera

Fig. 5.31

Roger Ressmeyer/Corbis


U.S. Active Volcanoes


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