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VolcanoesLesson #10 Volcanoes

Objective: Describe the main features and characteristics of volcanoes. Be

explain to name and explain the three separate types.

! Volcano: An opening in the earth's crust through which molten magma and gases erupt.

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! Ring of Fire: A zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.

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Where do volcanoes occur?

! Occur at convergent boundaries ! In subduction zones

4

! Composite or Stratovolcano.

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! Mount Saint Helens

Yellowstone National Park

Largest volcano

on the planet

Caldera

! Caldera Volcano: Large crater caused by the violent explosion of a volcano that collapses into a depression.

! Supervolcano: A volcano capable of producing a super volcanic eruption with ejecta greater than 1000 cubic kilometers.

! This is the range of serious destruction if the Yellowstone Supervolcano were to erupt.

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! Explosions happen about “every 600,000 years at Yellowstone,"

! "And it's been about 640,000 years since the last super explosive eruption there."

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! The Hot Spot under the continent has erupted periodically throughout history.

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N. American

Plate

OlderToday

! The rest of the United States would be buried in 1 meter of Ash.

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! The rest of the United States would be buried in 1 meter of Ash. ! The global climate would shift for many years as dust

clouds would block out the sun. ! Agriculture would become difficult.

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! Which Island is the oldest? Youngest

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A

B

CD Only Island with active volcanoes

Older

ErosionIslands get smaller

New Earth/

Growth

! Hawaii is caused by a hot spot: A location above an upwelling of magma from the mantle.

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! Why do volcanoes erupt? ! When rock from the mantle melts, it moves

to the surface through the crust, and releases pent-up gases which can erupt.

! Activity! Volcanic Explosion. ! A volcano is a lot like a bottle of soda exploding. ! Like soda, molten earth contains gases. ! These gases create a frothy cloudy explosion. ! Note the air spaces in the volcanic rock Pumice. ! Make tube to drop entire pack at once.

or shake!

! Mt. Vesuvius ! Erupted violently August 24, 79 AD ! Molten debris engulfed the surrounding area. ! Suffocating the inhabitants of the neighboring

Roman cities of Pompeii, Herculaneum and Stabiae. ! The cities remained buried and undiscovered for

almost 1700 years until excavated. ! These excavations continue today and provide

insight into life during the Roman Empire

! Mt. Vesuvius ! The eruption claimed many lives. Many of the

inhabitants were preserved under the volcanic debris.

! Mt. Vesuvius ! Millions currently live next to this active volcano.

! Mt. Vesuvius ! Millions currently live next to this active volcano.

! The cataclysmic explosion of Krakatoa was heard as far away as Western Australia, about 1,930 miles. ! 36,417 (official toll) people died. ! 13,000 times the yield of the atomic bomb that

devastated Hiroshima, Japan.

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K r a k a t o a w a s h e r e .

! Pyroclasitc flow: A fast-moving avalanche of hot lava fragments.

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! Pyroclastic rock: Rock ejected from a volcano. (Volcanic Bombs)

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! Lahar: A flow of volcanic ash and water.

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! A lahar is often produced when a snow-capped volcano erupts and hot pyroclastics melt a large amount of snow or ice.

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Snowmelt mixed with ash

Crater

A crater is a steep walled depression located at the summit of a volcano. A crater can also be produced by a meteorite impact.

Acid lakes

Sulfuric acid and

hydrogen chlorides

CraterCaldera

A caldera is a large depression in a volcano formed either by the collapse of the top of a composite volcano after an explosive eruption, or from the collapse of the top of a shield volcano after the magma chamber is drained.

Crater Lake

What are the purpose of Volcanoes?

31

! New Land is formed.

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! Release of healthy gases.

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Water and

Carbon Dioxide

! Volcanic ash fertilizes land.

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! Volcanic eruptions formed oceans and early atmosphere.

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