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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



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.



Types of Lava

Aa Lava



Fig. 5.3

Kim Heacox/DRX

Columbia Plateau Flow Basalts

Fig. 5.2

Martin G. Miller

Pyroclastic flow


Mudflow (lahar)


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



in the


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




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





Lyn Topinka/USGS

Alternating pyroclastic layers and lava flows

Slopes intermediate in steepness

Intermittent eruptions over long time span

Mostly andesite


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


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


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



Mt. Pelée


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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