Volcanoes and Hot Spots

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Volcanoes and Hot Spots

• http//news.bbc.co.uk/2/hi/science/nature/4972366.
  stm

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Volcanoes

• Beneath the volcano, molten rock filled with
  gases collects in the magma chamber.
• Magma pushes through cracks in the Earths
  surface and rises up into the volcanoes vent.
• Tremendous heat and pressure build up.

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What is a Volcano

• Volcanoes are pressure valves that release energy
  from deep within the Earth.

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The Pressure

• The pressure becomes so great the mountaintop
  literally blows off.
• Ash and rock shoot high into the air forming a
  big cloud.
• Lava flows from the vent and its branches.

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Pyroclastic Flow

• The explosion of rock and magma from a volcano is
  called its pyroclastic flow.
• The amount of heat and pressure from the
  explosion affects the viscosity of the fluid.
• Viscosity is a measure of fluidity is it sticky
  or does it flow easily.

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The World's Deadliest Volcanoes

• Just as seismologists measure the size of an
  earthquake using the Richter scale
• Volcanologists use an eruption magnitude scale
  called the Volcanic Explosivity Index, or VEI to
  classify eruptions.

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Volcanic Explosivity Index

• This scale assigns a number to an eruption based
  on things that can be observed, such as the
  height of an eruptive plume and the volume of the
  materials erupted.
• http//www.pbs.org/wgbh/nova/vesuvius/deadliest2.h
  tml

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Types of volcanoes

• Stratovolcanoes are built from several layers of
  viscous (sticky) magma.
• These volcanoes have relatively steep sides and
  can grow to great heights.
• Mount Vesuvius which destroyed Pompeii and Mt.
  Saint Helens are examples.

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Cinder Volcanoes

• Cinder cone volcanoes are relatively small (less
  than 1,000 feet high) with very steep sides.
• They are built from piles of ejected rock
  fragments.
• Italys Stromboli and Mexicos Paricutin are two
  examples.

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Shield Volcanoes

• Shield volcanoes are massive with gently sloping
  slides.
• They build up from the sea floor.
• These are the largest volcanoes on Earth.
• Shield volcanoes are built from several layers of
  fluid, runny lava (non-viscous).
• These volcanoes are island builders.
• Mauna Loa in Hawaii runs 60 miles long and 30
  miles wide.

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Calderas

• The largest and most explosive volcanic eruptions
  eject tens to hundreds of cubic kilometers of
  magma onto the Earth's surface.
• When such a large volume of magma is removed
  from beneath a volcano, the ground subsides or
  collapses into the emptied space, to form a huge
  depression called a caldera.
• Some calderas are more than 25 kilometers in
  diameter and several kilometers deep.

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Caldera

• Calderas are among the most spectacular and
  active volcanic features on Earth.
• Earthquakes, ground cracks, uplift or subsidence
  of the ground, and thermal activity such as hot
  springs, geysers, and boiling mud pots are common
  at many calderas.
• Although most caldera unrest does not lead to an
  eruption, the possibility of violent explosive
  eruptions warrants detailed scientific study and
  monitoring of some active calderas.

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• A hot spot is an area of persistent volcanic
  activity.
• Hot spots originate at unusually hot areas of the
  mantle-core boundary.
• Overlying mantle melts forming plumes of magma
  that rise and penetrate the crust forming
  volcanoes.
• Hawaii, Iceland, and Yellowstone are examples of
  hot spots.
• Hot spots are generally characterized by large
  outpourings of basaltic lava for relatively long
  periods of time.

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Hot Spots

• Beneath Yellowstone Park is a close to the
  surface magma chamber so massive that a full
  scale eruption could dwarf any previous volcanic
  eruption in history.
• http//dsc.discovery.com/convergence/supervolcano/
  interactive/interactive.html

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Hawaiian Islands

• http//www.classzone.com/books/earth_science/terc/
  content/investigations/es0810/es0810page03.cfm
• Natural Phenomena Geysers Lava and Hot Spots

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• http//www.iknowthat.com/com/App?FileScienceLab.h
  tmTypeSSWFvolcano2Fscience_deskAppScienceL
  ab
• http//dsc.discovery.com/convergence/pompeii/inter
  active/interactive.html