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DESCRIPTIONVolcano 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
Volcano FlavorsMmmmmm. Volcanoes.
2Todays Agenda:What causes a Volcano?Magma vs. LavaViscosityFlow Rate and Silica ContentExplosivityAnatomy3 Types of Volcanoes (Flavors!)Types of Lava RocksFAQ
Causes of Volcanoes:
1) Convergence (continental & island arcs)2) Divergence (mid-ocean ridges and continental rift valleys)3) Hotspot / plume (oceanic island chains)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.
ViscosityViscosity = ThicknessHigh Viscosity = Very Thick, ChunkyLow Viscosity = Very Thin, Runny
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 / TimeSilica ContentThe Elements Silicon and Oxygen combine to make Silica
Silica is the most common element in the Earths Crust
Silica is lightweight and makes magma and lava thickerExplosivityIn pairs, discuss the answers to the following questions. Be ready to share with the class.
Why do some volcanoes explode more violently than others?If a volcano has thick lava (high viscosity) will it be more or less explosive than a volcano with thin lava (low viscosity)?Volcano Anatomy
Magma ChamberMain VentSide VentDikeTephraAshCalderaFissuresLava103 Main Types of VolcanoesShield Volcano
Composite / Stratovolcano
Cinder ConeShield VolcanoProperties of a Shield VolcanoLow 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
Example: Mauna Loa, HawaiiLargest active volcano in the worldStands 5.5 miles high
Flavor: Chocolate SyrupVideo of a Shield Volcano
Composite / StratovolcanoProperties of a Composite or StratovolcanoMedium 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 doesnt flow farLayers of lava and ash built upon each otherUnpredictable bursts of activity
Examples: Mt. St. Helens andMt. Rainier, Washington StateMakes up the largest percentage of Earths volcanoes (60%)
Flavor: Marshmallow FluffVideo of Composite / Stratovolcano
Cinder ConeProperties of aCinder ConeHigh 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 unpredictableExample: Paricutin, Mexico1943, Grew 300 ft in 5 days
Flavor: Cookie CrumbleVideo of a Cinder Cone
BasaltAndesiteRhyolite 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 (1400-1700F) Light Color
High Silica Content(more than 68%)
High Viscosity Lava
Low Flow Rate (barely flows)
Low eruptive temp(1,200-1,400 F)24Which lava rocks form at each type of volcano?Basalt = Shield Volcanoes
Andesite = Composite/Stratovolcano
Rhyolite = Cinder Cones
What kind of Volcano is this?26
Biggest Volcano in our Solar SystemWhat type of volcano is this?
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.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 doesnt 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.
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 its active, probably pretty cheap. But if you wait until it is dormant, itll be very expensive. Good farming land and allQ: 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 activeThis number is from the Smithsonian Institution book, Volcanoes of the World: Second Edition compiled by Tom Simkin and Lee Siebert.
My favorite Question:Q: What I want to know about volcanoes is why is it that volcanoes erupt lava? Why cant 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 doesnt leave much behind so it cannot make a volcano. When rock melts and erupts, it solidifies and leaves behind lava that forms the volcano.