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Volcano Flavors Mmmmmm…. Volcanoes….

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Volcano Flavors. Mmmmmm …. Volcanoes…. Eyjafjallajökull. Today’s Agenda :. What causes a Volcano? Magma vs. Lava Viscosity Flow Rate and Silica Content Explosivity Anatomy 3 Types of Volcanoes (Flavors!) Types of Lava Rocks FAQ. Causes of Volcanoes: - PowerPoint PPT Presentation

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Page 1: Volcano Flavors

Volcano Flavors

Mmmmmm…. Volcanoes….

Page 2: Volcano Flavors

Eyjafjallajökull

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Today’s Agenda:What causes a Volcano?Magma vs. LavaViscosityFlow Rate and Silica ContentExplosivityAnatomy3 Types of Volcanoes (Flavors!)Types of Lava RocksFAQ

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Causes of Volcanoes:1) Convergence (continental & island arcs)2) Divergence (mid-ocean ridges and continental rift valleys)3) Hotspot / plume (oceanic island chains)

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Magma vs. Lava?Magma is melted rock with gasses

inside that is BELOW the surface.

Lava is what we call the melted rock when it escapes into the AIR. Gas is usually released from the lava while it cools into a rock.

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ViscosityViscosity = ThicknessHigh Viscosity = Very Thick, ChunkyLow Viscosity = Very Thin, Runny

HighViscosity

LowViscosity

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Flow RateHow fast lava flows some distance over some time

depends on its viscosity.

High flow rate = fast, fluid, thin = Low ViscosityLow flow rate = slow, chunky, thick = High

Viscosity

Flow Rate = Distance Lava Flows / Time

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Silica ContentThe Elements Silicon and Oxygen combine to

make Silica

Silica is the most common element in the Earth’s Crust

Silica is lightweight and makes magma and lava thicker

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ExplosivityIn pairs, discuss the answers to the following

questions. Be ready to share with the class.

1. Why do some volcanoes explode more violently than others?

2. If a volcano has thick lava (high viscosity) will it be more or less explosive than a volcano with thin lava (low viscosity)?

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Volcano Anatomy

Magma Chamber

Main Vent

Side Vent

Dike

Tephra

Ash

Caldera

Fissures

Lava

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3 Main Types of VolcanoesShield Volcano

Composite / Stratovolcano

Cinder Cone

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Shield Volcano

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Properties of a Shield Volcano

Low Viscosity LavaLow Silica Content in LavaLava flows very far and fastNot very explosive – actually quiet and gentleBecause the Lava is not very viscous, gasses

escape easily from the lavaGently Sloping sides, very wide baseFlows continuously for a long time

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Example: Mauna Loa, HawaiiLargest active volcano in the world

Stands 5.5 miles high

Flavor: Chocolate Syrup

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Video of a Shield Volcano

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Composite / Stratovolcano

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Properties of a Composite or Stratovolcano

Medium Viscosity LavaMedium Silica Content in LavaLava flows slow and not very farVERY explosive and dangerousGasses are trapped by the viscous lava and build

up pressureSteep sides because the lava doesn’t flow farLayers of lava and ash built upon each otherUnpredictable bursts of activity

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Examples: Mt. St. Helens andMt. Rainier, Washington State

Makes up the largest percentage of Earth’s volcanoes (60%)

Flavor: Marshmallow Fluff

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Video of Composite / Stratovolcano

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Cinder Cone

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Properties of aCinder Cone

High Viscosity magmaVery high Silica ContentMost of the volcano is formed by ash and small

lava chunksLava does not flow, but builds up in one spotMedium-High explosivity, massive amounts of ashVery steep sidesDevelops very quickly and is unpredictable

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Example: Paricutin, Mexico1943, Grew 300 ft in 5 days

Flavor: Cookie Crumble

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Video of a Cinder Cone

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Basalt Andesite Rhyolite

• Dark Color

• Low Silica Content (less than 52%)

• Low Viscosity Lava

• High Flow Rate (can travel far)

• Hottest eruptive temp (1700+ °F)

• Intermediate lava

• Med Silica Content (57%)

• Med Viscosity Lava

• Intermediate Flow Rate (flows more than rhyolite, but not as easily as basalt)

•Medium Temperature (1400-1700°F)

• Light Color

• High Silica Content(more than 68%)

• High Viscosity Lava

• Low Flow Rate (barely flows)

• Low eruptive temp(1,200-1,400 °F)

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Which lava rocks form at each type of volcano?

Basalt = Shield Volcanoes

Andesite = Composite/Stratovolcano

Rhyolite = Cinder Cones

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Eyjafjallajökull

What kind of Volcano is this?

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Olympus Mons

Biggest Volcano in our Solar System

What type of volcano is this?

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Bonus Answers to FAQ:Q: How deep do volcanoes go?A: The magma chambers we can detect are

usually between 1 and 10 kilometers deepQ: How deep can you travel into a volcano?A: We do not have the ability to travel in magma.

Yet.Q: How old are volcanoes?A: This varies. Many can last for millions of years.

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Q: Why do volcanoes have craters?A: Several reasons: When the magma chamber

empties, the ground above it collapses. Also, big explosions can blow material away from the volcano, leaving behind a crater. Fun fact: this doesn’t always happen at the top.

Q: What can we gain from volcanoes?A: Volcanic ash is temporarily unpleasant, but

leaves behind very fertile farming land in the long run.

Q: If all the volcanoes in the world erupted, would we die?

A: Yes.

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Q: How/why do volcanoes become dormant (no longer active)?

A: When the magma chamber empties or solidifies, there is no more magma to rise out of the volcano. Also, if it is a hot spot volcano, it can move away from the hot spot.

Q: How much would a volcano cost if you could buy it?A: While it’s active, probably pretty cheap. But if you

wait until it is dormant, it’ll be very expensive. Good farming land and all…

Q: How many active volcanoes are there?A: The best guess is 1511 volcanoes have erupted in

the last 10,000 years and should be considered active

This number is from the Smithsonian Institution book, “Volcanoes of the World: Second Edition” compiled by Tom Simkin and Lee Siebert.

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My favorite Question:Q: What I want to know about volcanoes is

why is it that volcanoes erupt lava? Why can’t it just be like water or something else?

A: When water is heated and erupts from the surface, we call it a geyser. Water flows away or evaporates and doesn’t leave much behind so it cannot make a volcano. When rock melts and erupts, it solidifies and leaves behind lava that forms the volcano.

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Geyser