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Volcanoes - Types & Volcanic Hazards

Everything about volcanoes, their types and different volcanic hazards. Complete with high definition images. Enjoy!

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Volcanoes - Types & Volcanic Hazards

  1. 1. VOLCANOES Presented by: Abinash Acharya
  2. 2. • It is point on the earth’s crust where magma forces its way to the surface due to pressure. • Ash and gases may also escape during a typical volcanic eruption. What is a volcano?
  3. 3. Location Of Volcanoes
  4. 4. Layout Of A Volcano
  5. 5. Types Of Volcanoes Acid Volcanoes • Highly explosive • Magma/lava is viscous (thick) • Found where oceanic crust is subducted under continental crust Basaltic Volcanoes • Less explosive* • Magma/lava less viscous (runny) • Found at rift zones (constructive boundaries) and hotspots
  6. 6. Acid Volcanoes Lava Domes • Formed of layers of lava high in silica • Lava is viscous and does not flow very far • Rounded Form • Composed completely of lava Stratovolcanoes • Also called composite volcanoes • Formed of layers of lava and ashes • Lava is viscous • Distinct cone shape
  7. 7. LAVA DOMES-EXAMPLE Mount Chaiten, Chile
  8. 8. STRATOVOLCANO-EXAMPLE Mount St. Helen, US (Before and after)
  9. 9. Basaltic Volcanoes • Also known as shield volcanoes • Consists of widespread layers of lava and have low viscosity • Silica content is low • Low form spread over a great distance
  10. 10. Basaltic Volcano-Example Eyjafjallajökull, Iceland
  11. 11. Calderas Volcanoes • Collapsed Volcanoes • Magma chamber has emptied and the ground has sunk • Often becomes a lake • New volcanoes can form, or pressure can build from below, lifting the ground • If acidic, this can cause a catastrophic eruption in the form of a ’Super Volcano’
  12. 12. Calderas-Example Mount Pinatubo, Phillipines
  13. 13. Hotspots • Tectonic plate moves over a magma plume • Occasionally erupts, creating a volcano
  14. 14. Major Hotspots
  15. 15. Volcanic Explosivity Index (VEI) TYPE DESCRIPTION EXAMPLE Hawaiian Gentle Kilauea Strombolian Explosive Stromboli Vulcanian Severe Nabro Peléan Cataclysmic Mt.Pelée Plinian Paroxysmal St.Helens Plinian/Ultra-Plinian Colossal Krakatoa Ultra-Plinian Super-Colossal Tambora Supervolcanic Mega-Colossal Yellow Stone Number 8 has never been experienced in human history The list has been simplified. See correct details here:
  16. 16. Volcanic Activity Index
  17. 17. Volcanic Hazards Most hazards during eruptions are caused by what comes out of a volcano. In the next few slides, we’ll be seeing the different types of volcanic hazards.
  18. 18. Volcanic Hazards – Lava Flows • Mostly associated with basic volcanos • Slow moving 1 – 5 km/h • Low risk to human life • Cover large areas and destroy large amounts of infrastructure
  19. 19. Hazards – Pyroclastic Flows • Hot clouds of ash and gas • Move downhill, close to the ground, following valleys • High speed – up to 500 km/h • As far as 30 km • Up to 7000 C • Highly dangerous
  20. 20. Hazards - Lahars • Occur on high volcanos covered in snow and ice, or wet mud/soil • Eruption causes snow to melt, or lava mixes with mud • Flows downhill like wet concrete
  21. 21. Hazards – Ash Clouds • Slow moving • Weight of ash can collapse buildings • Destroys crops, pollutes water • Affects air traffic • Can enter high atmosphere and cause cooling – disrupting climate
  22. 22. Hazards – Lava Bombs • Molten rocks thrown out of volcano • Pummice – smaller rocks • Travel short Distances • Can Start Fires
  23. 23. Benefits Of Living Near a Volcanic Region • Aesthetic beauty eg. Mount Fuji, Japan • Mining of minerals and diamonds • Geothermal energy and hot springs • Highly fertile soils – soft rocks and high mineral content
  24. 24. Predicting Volcanic Eruptions • Monitoring seismic disturbances (tremors) • Changes in volcano profile (shape) • Chemical changes in groundwater • Emissions of gases • Thermal monitoring (temperature)
  25. 25. History Of Eruptions • 1800 BC – destruction of Bronze age settlements – then several more times • 79 AD – destruction of Pompeii • At least 40 times until the last eruption in 1944 – witnessed by allied troops towards the end of WWII • = once every 40-50 years
  26. 26. Reducing The Risks • Round-the-clock monitoring of the volcano: Tremors, gases, changes in water • Identifying hazard areas: Weak spots, secondary vents, predicting routes of pyroclastic flows • Creating an evacuation plan: Zoning, warning systems, public education
  27. 27. References • CSE+Plate+Tectonics+and+GCSE+Plate+Te ctonics • • als/chapter10.html •