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: 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.

Viscosity Viscosity = Thickness High Viscosity = Very Thick, Chunky Low Viscosity = Very Thin, Runny High Viscosity Low Viscosity

Flow Rate How fast lava flows some distance over some time depends on its viscosity. High flow rate = fast, fluid, thin = Low Viscosity Low flow rate = slow, chunky, thick = High Viscosity Flow Rate = Distance Lava Flows / Time

Silica Content The 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

Explosivity In 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 Chamber Main Vent Side Vent Dike Tephra Ash Caldera Fissures Lava

3 Main Types of Volcanoes Shield Volcano Composite / Stratovolcano Cinder Cone

Shield Volcano

Properties of a Shield Volcano Low Viscosity Lava Low Silica Content in Lava Lava flows very far and fast Not very explosive – actually quiet and gentle Because the Lava is not very viscous, gasses escape easily from the lava Gently Sloping sides, very wide base Flows continuously for a long time

Example: Mauna Loa, Hawaii Largest active volcano in the world Stands 5.5 miles high Flavor: Chocolate Syrup

Video of a Shield Volcano

Composite / Stratovolcano

Properties of a Composite or Stratovolcano Medium Viscosity Lava Medium Silica Content in Lava Lava flows slow and not very far VERY explosive and dangerous Gasses are trapped by the viscous lava and build up pressure Steep sides because the lava doesn’t flow far Layers of lava and ash built upon each other Unpredictable bursts of activity

Examples: Mt. St. Helens and Mt. Rainier, Washington State Makes up the largest percentage of Earth’s volcanoes (60%) Flavor: Marshmallow Fluff

Video of Composite / Stratovolcano

Cinder Cone

Properties of a Cinder Cone High Viscosity magma Very high Silica Content Most of the volcano is formed by ash and small lava chunks Lava does not flow, but builds up in one spot Medium-High explosivity, massive amounts of ash Very steep sides Develops very quickly and is unpredictable

Example: Paricutin, Mexico 1943, Grew 300 ft in 5 days Flavor: Cookie Crumble

Video 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 ( °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)

Which lava rocks form at each type of volcano? Basalt = Shield Volcanoes Andesite = Composite/Stratovolcano Rhyolite = Cinder Cones

Eyjafjallajökull What kind of Volcano is this?

Olympus Mons Biggest Volcano in our Solar System What 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 deep Q: 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 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.

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.

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.

Geyser