I. Volcano Zones

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II. Causes of Volcanoes

Divergent Rift zones – when tectonic

plates separate.

Subduction zones - plates dive into

asthenosphere and melt.

Hot spots – hot convection areas that melt

through a tectonic plate.

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III. Magma Properties & Volcanoes

Magma Properties

Magma & Volcano Types

Granite

Composite Volcanoes

Basalt

Shield Volcanoes

Eruption Classification Violent Quiet

Silica Content High Low

Viscosity (thickness) High Low

Water Content Highest Lowest

Tendency to form lava Least Highest

Tendency to form pyroclastics Highest Least

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VIII. Volcano Size Comparisons

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IV. Composite Volcano (Strato)

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V. Composite Volcanoes:

Magma & Structure

Magma - High water & silica content,

thick lava that traps gases, very

explosive

Forms steep sides

Second largest volcano type

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Violent Eruptions

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Mt. Hood

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Mt. Fugi

VI. Shield Volcanoes

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VII. Shield Volcanoes

Magma – Low water & silica content,

runny lava that releases gases, not

explosive

Forms flat or shield-like volcanoes

Largest volcano type

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Quiet Eruptions

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Shield Volcanoes

Mona Loa, Hawaii

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Shield Volcanoes

Volcanoes of Mars

IX. Cinder Cone

Smallest volcano

Formed from Pyroclastic Material

Often found on sides of Composite and

Shield Volcanoes

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X. Hot Spot Volcanoes

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XI. How Hot Spot Volcanoes form

Magma rises from asthenosphere

Tectonic plates move over hot spot

Creates a line of Volcanoes

Examples: Hawaii & Yellowstone

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Yellowstone’s Track

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X. Predicting Eruptions

Measure Magmatic Earthquakes

Tiltmeters – measures slope of volcano

Measure volcanic gases

Measure temperature from orbit

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