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Introduction to Volcanoes: Types, Hazards, and Predictions

Explore the world of volcanoes and learn about their types, hazards, and how to predict eruptions. Discover the geological formations, magma compositions, and the positive aspects of volcanoes.

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Introduction to Volcanoes: Types, Hazards, and Predictions

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  1. Chapter 12 Volcanoes

  2. Introduction • A volcano is the opening in the Earth that erupts gases, ash and lava. • There are over 1500 volcanoes in the world. • Over 600 are currently active. • 169 volcanoes in the Unites States are currently active. Being monitored by the USGS • Kilauea in Hawaii is the most active (but not explosive) volcanoes on Earth • Check out chart on 346 – why not explosive?

  3. Mauna Loa on Hawai'i Big Island (active) is world’s biggest volcano.

  4. Olympus Mons is a shield volcano that towers to an amazing 26 km. That makes it 3 times the height of Mt. Everest. Unlike Everest, Olympus Mons has a very gentle slope. It is up to 550 km at its base.

  5. Active – Dormant - Extinct • Active – is a volcano that has had at least one eruption during the past 10,000 years. May be dormant or erupting. • Dormant – have note erupted recently, but may at any time • Extinct – have not erupted in over 10,000 years.

  6. Since 1980, 45 eruptions and 15 cases of notable volcanic unrest have occurred at U.S. volcanoes. t 3 • Many volcanoes are found underwater. • Where are a good deal of these located? • In some cases, lava can build up high enough to form islands (Hawaii, Iceland) • Test question - tell what creates the volcanoes at each of the locations on the following slide.

  7. Types of magma • Basaltic • 42-52% silica content • Dark in color • Low viscosity • Non-Explosive • Low gas content • Andesitic • 52-66% silica content • Granitic: • >66% silica content • Lighter in color • High viscosity • High gas content • Explosive

  8. Viscosity • A liquid’s ability to resist flow • Related to SiO2 - More silica = more viscosity • Low viscosity – runny - watery • High viscosity – thick - milkshake

  9. Magma composition • Page 350 • Be able to classify the three types of magma based on their silica content. • Volcano Apps WK – quiz next week • Thursday or Friday

  10. Types of volcanoes • Shield: gentle-sloped, quiet eruptions, basaltic lava, low sillica-content, low trapped-gas content. Kilauea. • Composite: made of both lava and tephra. Mount Rainier. • Cinder cone: steep-sloped, made of tephra, explosive, granitic lava, high silica, high trapped gases. Krakatoa.

  11. Hazards from volcanoes • Lava (enough said) • Volcanic ash - can cause lung cancer, can also smother crops and cause other damage • Pyroclastic flows • Lahars • Poisonous gases - sulfuric gases (rotten eggs). Can also combine with water vapor to create sulfuric acid and cause acid rain • Can cause tsunamis

  12. Pyroclastic Flows • Flow of extremely hot material including ash, poisonous gas and tephra. • Can reach 700 km/h (450 mph).[2] The gas can reach temperatures of about 1,000 °C (1,830 °F). • #1 cause of volcano-related deaths • (29,000 at Mount Pelee 1902)

  13. Lahars • A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water • Vary in size, speed and deadliness. • Snow and glaciers can be melted by lava or pyroclastic flows during an eruption. • The 1991 eruption of Mount Pinatubo caused lahar flows: the first eruption itself killed six people, but the lahar flows killed more than 1500.

  14. Predicting volcanic eruptions • There can be several signs that sometimes help predict the eruption of an earthquake and necessitate evacuation: • Seismic activity • Bulging of volcano’s exterior • Gas Emissions • Thermal monitoring • Mass movements

  15. Plus Sides to volcanoes • New Land • Fertile Soil • Geothermal Energy • Mineral Resources • aluminum, diamonds, gold, nickel, lead, zinc, and copper. • Tourism • Spas and resorts

  16. Volcano: an opening in the Earth where lava, ash and gas escapes

  17. Tephra: rock thrown into the air • http://www.webpages.uidaho.edu/~simkat/cors220_files/tephra_sizes.jpg • http://vulcan.wr.usgs.gov/Imgs/Gif/Hazards/Tephra/tephra_plot_distance.gif

  18. Shield: gentle-sloping volcano, generally display quiet eruptions

  19. Crater - a circular depression in the ground caused by volcanic activity

  20. Vent: opening of a volcano

  21. Dike: a vertical igneous rock formation.

  22. Magma: hot, melted rock beneath the surface.

  23. Caldera: large crater formed when a volcano collapses

  24. Cindercone- steep sided volcano known for explosive eruptions

  25. Neck: a solid igneous core that remains after the volcano has been eroded.

  26. Batholith: intrusive igneous rock formed under ground

  27. Composite- volcano made of both lava and tephra

  28. Sill- horizontal igneous rock formation

  29. Pluton - any type of igneous rock intrusion

  30. Hot spot- place above an exceptionally hot part of the mantle. (not at plate boundaries)

  31. Tephra • First, what type(s) of volcano erupts tephra as a product? • Classified by size • Ash - particles smaller than 2 mm (0.08 inches) in diameter • Lapilli or volcanic cinders - between 2 and 64 mm (0.08 and 2.5 inches) in diameter • Volcanic bombs or volcanic blocks - larger than 64 mm (2.5 inches) in diameter.

  32. Where do volcanoes occur? • See map, page 337 • Divergent boundaries • Subduction zones • Hot spots • Know two realistic examples of each

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