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Chapter 12Earthquakes and Volcanism

I. VolcanismI. VolcanismA. DefinitionsB. Volcanic SettingsC. Types of Volcanoes

II. Current Volcanic Activity

Chapter 12Earthquakes and Volcanism

Deadliest Volcanic Eruptions Since 1500 A.D.

Eruption Year CasualtiesMajor Cause

Nevado del Ruiz, Colombia 1985 25,0001,3 Mudflows3

Mont Pelée, Martinique 1902

30,0001

(29,025)2Pyroclastic

flows2

K k t I d i 188336,0001

(36 417)2 T i2

Benefits of a volcano:• Fertile soils (Hawaii)• Geothermal Energy (Iseland,

Italy, New Zealand)• Real Estate (Iceland, Japan)

Krakatau, Indonesia 1883 (36,417)2 Tsunami2

Tambora, Indonesia 1815 92,0001,2 Starvation2

Unzen, Japan 179215,0001

(14,030)2

Volcano collapse,

Tsunami2

Lakagigar (Laki), Iceland 1783 9,0001 (9,350)2 Starvation2

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I. VolcanismA. Definitions

Volcano: Forms at the end of a central vent or pipe that rises from the asthenosphere and upper mantle throughrises from the asthenosphere and upper mantle through the crust into a volcanic mountain.

Generally a conical shaped hill or mountain built by accumulations of lava flows, tephra, and volcanic ash

I. VolcanoesB. Volcanic Settings

Figure 12.24

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I. VolcanismC. Types

Volcanic Landforms:

Ci dTypes of eruptions:

Cindercone

Caldera

Shield volcano

Plateau basalt

Composite volcanoes

• Effusive• Explosive

I. VolcanoesC. Effusive Eruptions

Effusive eruptions are relatively gentle ones that produce l f l i t d ith b lt l tenormous plumes of lava, associated with basalt plateaus

and shield volcanoes.

(Part of the Kilauea

Volcano in Hawaii)

Figure 12.32

)

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I. VolcanoesC. Effusive Eruptions

Plateau basalt: These volcanoes produce a very fluid basaltic magma with horizontal flows. The form of these volcanoes is flat to gently sloping.

Figure 12.24

I. VolcanoesC. Effusive Eruptions

Shield volcanoes are very large slightly sloping volcanoes, 6 to 12° that have gently flowing magmas12 , that have gently flowing magmas.

Figure 12.24

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I. VolcanoesC. Effusive Eruptions

Figure 12.32

II. VolcanoesC. Explosive Eruptions

Explosive eruptions are produced from volcanic activity inland from subduction zones.

Figure 12.32

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I. VolcanoesC. Explosive Eruptions

A cinder cone is a small volcano, between 100 and 400 meters tall, made up of exploded rock blasted out of a central vent at atall, made up of exploded rock blasted out of a central vent at a high velocity

Figure 12.24

Hualalai Volcano

I. VolcanoesC. Explosive Eruptions

Figure 12.24Long Valley Caldera in California

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I. VolcanoesC. Explosive Eruptions

Composite Volcano

Figure 12.34

I. VolcanoesC. Explosive Eruptions

Composite Volcano

Mt. Vesuvius, Italy79 A.D.

St. Augustine, Alaska

Iceland

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I. VolcanoesC. Explosive Eruptions

Composite Volcano

Mt Pi t b Phili iMt. Pinatubo, Philippines• 800 deaths• 15-20 million tons of ash and sulfuric acid

mist were blasted into the atmosphere• Reduction in Earth’s albedo• Decrease in global temperatures

I. Composite Volcanoes

Figure 12.34

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I. Volcanoes

Animations WebsiteAnimations Website

II. Current Volcanic Activity

http://volcanoes.usgs.gov/

http://volcano.und.edu/