VOLCANOES

Chapter 13 Part 2

IV. Types of Volcanoes

e.g. Hawaiian Islands are examples of Shield Volcanoes

A. Shield Volcanoes1. Eruption: Non-explosive2. Formation: repeated lava

flows wide and short

IV. Types of Volcanoes

B. Cinder Cone Volcanoes1. Eruption: Explosive2. Formation: pyroclastic materials not

cemented together angle (∠) of repose = 30-40° ∠ that

is the steepest ejecta can pile up w/out sliding downhill narrow but tall

IV. Types of Volcanoes

C. Composite Volcanoes (Stratovolcano)

1. Eruption: Alternating Explosive w/ Non-Explosive

2. Formation: alternating lava flows w/pyroclastic materials

IV. Types of Volcanoes

C. Composite Volcanoes (Stratovolcano)

3. Dangers: a) Nuee ardente (aka glowing avalanche)

= ash + steam flow @ 125 mph downhill

b) Lahars = volcanic debri + water flow (due to melting snow or rainfall) mix flow downhill @ tremendous speed

IV. Types of Volcanoes

D. CalderasA. Magma chamber empties overlying

rock loses support collapses looks like a bowl sitting on earth

B. Often fills with H2O e.g. Crater Lake, OR

C. Can repeat process e.g. Crater Lake now has a

small composite volcano in its center

V. Effects of Volcanoes on Earth Destruction of property Alteration of climate, even in remote

areas Coats leaves of plants Clogs waterways Buries vegetation Lahars Great extinction of life due to cooler

climate

VI. Predicting Volcanic Eruptions

Geothermal image of lava flows at Kilauea Volcano, Hawaii

A. Earthquake activitya) Seismographs detect shifting of

magma

B. Temperature Changesa) Geothermal imaging of

satellites detect magma rising to surface

VI. Predicting Volcanic Eruptions

C. Surface Bulgesa) Tilt meters detect pressure increases

caused by magma rising to surface

D. Measuring output of volcanic gases