Volcano fundamentals

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Volcano fundamentals
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Section goals

• Recognize that there are different types of
  volcanoes.
• Identify volcanic products emitted during
  eruptions.
• Explain how the properties of the magma influence
  the explosivity, type, and shape of volcanoes.
• Explain how the products of volcanic activity
  influence both long-term and short-term changes
  to earth systems.
• Recognize that scientific knowledge changes over
  time and that theories are repeatedly reexamined
  in the face of new evidence.
• Understand that scientists publish their work and
  collaborate to enhance their understanding.

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Movie clip

• 2 volcanologists are at a conference to find ways
  to convince people at their volcano can erupt
  with deadly results
• Soufriere Hills, Montserrat in the Caribbean.
  Eruption in the 1980s
• Watch for the pyroclastic flows!

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Questions on 2 movies from Wednesday
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Volcanoes

• Definition
• An opening on the earths surface through which
  molten rock flows and the material that builds up
  around
• Location
• Most are formed near plate boundaries or hot
  spots

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Parts of a volcano

• Vent opening where molten rock is pushed out to
  the surface of earth
• Magma Chamber - Chamber below volcano, holds the
  molten rock used in eruption
• Cone mound created from solid material released
  from previous eruption
• Crater hole (depression) at the top of volcano
  created by volcanic explosion
• Caldera depression left on top of the volcano
  created by the collapse of the magma chamber

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Types of volcanoes

• Shield Volcano Very large, non-explosive, lava
  poor in silicon, Hawaii, Iceland
• Cinder Cones Small, explosive , lava
  composition varies
• Stratovolcanoes (composite volcanoes) Large,
  explosive, Lava rich in silicon, Mt. St. Helens
• Calderas (Megavolcanoes) Largest Volcano
  Super explosive (apocalyptic), composition
  depends on location, Yellowstone, Toba

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Types of Volcanoes
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Shield Volcano

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Shield Volcano

• Shape (Not steep)
• Formed primarily by eruptions of lava
• Very Fluid lava
• Not Explosive in nature

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Cinder Volcano
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Cinder Volcano

• Very Steep
• Cone shaped
• Explosive in nature
• Tend to be smaller than the other types of
  volcanoes
• Made mostly of ash fall, ash flows

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Where do cinder volcanoes form?

• Small 10-100s m high
• Found on flanks of other types of volcano
• Not as much volcanic material-secondary vents

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Composite Volcanoes
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Composite volcanoes

• Also called stratovolcanoes
• Created by a combination of ash flows, and lava
  flows, produces layers (depends on location)
• Less fluid lava
• Very explosive
• Tend to be large volcanoes

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Where do Composite volcanoes form?

• Formed at Subduction zones

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Types of volcanoes

• Determined by
• Amount of emission
• Volcano Size
• Explosiveness
• Composition of emissions

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Calderas

• Formed when the magma chamber under the volcano
  collapses
• Huge explosion results in removal of volcanos
  top
• Not very fluid lava, mostly ash

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Megavolcanoes

• Much longer time between eruptions than regular
  volcanoes (100,000 years )
• Gigantic eruption when it occurs, different scale
  than other volcanos
• Ash covers 1000s of miles of land
• Can effect world climate, therefore all living
  things

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Type of eruption and volcano

• Determined by the chemical composition of the
  magma

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Chemical composition of lava

• Felsic
• Higher concentrations of silicon, potassium,
  sodium
• Much less dense
• Very viscous, does not flow well
• Created by strato-volcanoes and calderas

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Chemical composition of magma

• Mafic
• High in Iron, Calcium, and Magnesium
• Very dense
• Flows easily, comes out as lava
• Produced shield volcanoes

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Small scale physical indicators of a active
volcanic environment
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Features of an area with active volcanoes

• Fumaroles openings where hot gas and steam is
  released
• Geysers opening with a periodic eruption of hot
  water
• Mudpots opening that emits periodic eruptions of
  a combination of gas,water and mud

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Fumaroles
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Fumarole

• An opening in the earth that emit gases
• May be found some distance from the from the main
  vent
• Gases are heated by the volcanic sources, travel
  through cracks and fractures to surface

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Hot Springs
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Hot Springs

• Openings that are filled with water that is
  heated by nearby volcanic activity
• The water may range from mild to scalding, and
  include both helpful and toxic minerals

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Geyser
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Geysers

• A hot spring with specific ideal physical
  arrangement that allows it to periodically erupt
• No convection, cold water cap over volcanically
  heated water

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Geysers part 1

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Geysers, part 2
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Geysers, part 3
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Geysers, part 4
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Geysers

• Found near active and dormant volcanoes, which
  provide the underground heat source
• Rainwater goes underground, is heated to a gas,
  erupts (with water) out of a vent. Water loses
  heat and is recycled.
• Yellowstone, Iceland, and Japan have geysers

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Mud Pots
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Mud Pots

• Similar to a hot spring
• Form in places where water is scarce
• Mixture of a little water and volcanic ash

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Hydrothermal Vents
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Underwater volcanoes
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Hydrothermal vents

• Black/White Smokers found near underwater
  boundaries
• 380 Celsius temperature of smoke
• Hydrogen Sulfide cloud
• Bacteria is the base of the food chain, supports
  higher level creatures

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Photo of vent with Dudley
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Life at a black smoker
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Large worms
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Spider crab feeding on worms
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Hazards of volcanoes

• Ash Fall
• Pyroclastic Flows (Nuee Ardentes)
• Mud Flows (Lahars)

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Volcanic Hazards

• Tsunamis
• Climate change
• Additional issues

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Definition of Hazards

• Pyroclastic flows Combination of superheated
  gas, ash, and small rocks that flows up to 200
  mph down mountainsides
• Lahars Combination of hot water mixed with ash
  that flows up to 60 mph down the mountainsides
• Volcanic Bombs Hot pieces of volcanic rock shot
  out of the volcano during eruption

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Pyroclastic flow
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Lahars
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Note the mud on trees
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Hazards from the volcanic gases

• The expansion of gases as it is heated
• Produces most of the eruptive force of a ash
  volcano
• Water Vapor is the most common gas released
• Carbon Dioxide and Sulfur Dioxide are next

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Gas hazards related to volcanoes

• Lake Nyos,
• Cameroon, Africa
• 1986
• Release of Carbon dioxide
• Since CO2 is heavier than air it hugs the ground

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Constant release of gases

• Trees died by CO2 suffocation

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Ash Fall
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Ash Fall

• Carried by wind to great distances
• Causes problems with breathing, visibility, and
  machines
• Adds nutrients to the ground

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Climate Change form volcanic eruption

• Ash put into upper atmosphere
• Ash blocks sun
• Less heat lowers temperature
• Snow does not melt, glaciers grow

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Volcanic Bombs
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Volcanic Bombs

• Material thrown out from the eruption
• Range in size from pebbles to buses
• Can be hot, limited to the local area around vent

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Tsunami

• (Photo shopped)

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Volcanic Hazards

• Tsunamis
• Means Great Wave
• Not related to tides
• Generated mainly by underwater earthquakes
• or
• landslides that displace a lot of water
• or
• volcanic eruption in or under the water

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Tsunamis

• Generally more than one wave
• Wave is much wider than typical ocean wave (wall
  of water)
• Travels around 500 mph in open water, slows down
  as it nears shore
• Height increases as waves nears shore
• Some waves from Krakatoa reached over 100 ft tall

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• What are the differences between a tsunami and a
  ocean wave
• Height
• Breadth
• What it can carry
• Origin (ocean waves are generated by wind)

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Description of three types of lava flow

• Aa - chunky, sharp, clinking, made by rapid
  cooling of lava
• Pahoehoe - smooth or ropey texture, makes lava
  tubes, made by cooling lava at a slower rate
• Pillow- lava formed underwater, rounded edges

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Pillow lava
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• Explain why some lavas are runny and other are
  chunky

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Where are volcanoes found in the world?

• Convergent
• Divergent
• Other

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USGS Program

• View all volcanic eruptions over the last 1000
  years
• Patterns
• Are all the biggest volcanic eruptions located in
  one place ?

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World Volcanoes
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Volcano location

• Stratovolcanoes tend to be associated with a
  subduction zone where an ocean plate is moving
  under a continent
• Shield volcanoes tend to be associated with
  oceanic eruptions
• Cinder cones tend to be associated with divergent
  plate boundaries

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One other place of volcano formation

• Hot Spots
• Created because a narrow stream of hot mantle
  raises up from the core-mantle boundary
• Long lasting point of heat, stationary with
  respect to the plates
• If formed under ocean crust, creates an island arc

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Places where there might be a hot spot

• Hawaii
• Yellowstone
• Iceland
• Tahiti
• Up to 50 places in the world

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Where do quiet volcanoes form?

• Connected to hot spots
• Subduction boundaries related ocean to ocean
• Galapagos Islands
• Hawaiian islands
• Easter Islands
• Canary Islands

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Extraterrestrial Volcanoes
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Do volcanoes only exist on earth?

• What is needed to produce a volcano?
• How would the eruption of a volcano on a small
  moon differ from the earths eruptions?

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Extraterrestrial volcanoes

• Volcanoes not on earth
• Previous pictures were of Io, a moon orbiting
  Saturn.
• Io is the most volcanically active body in solar
  system.
• A plume of Sulfur chemicals can reach 60 to 100
  miles from surface of moon

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Comparison in size between Olympus Mons and Mauna
Loa
                                                                                                                                       
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Olympus mons
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Oympus Mons
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Facts about Olympus

• Largest volcano in the solar system
• Not active
• 370 miles wide, 16 miles high
• Cliffs rim the edge up to 3 miles high
• Generated by a hot spot

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Why is this volcano so much larger than others?

• Gravity (or lack of it)
• Plate Tectonics (or lack of it)

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Mount Olympus

• Largest volcano in solar system is on Mars
• Diameter of about 600 kilometers
• Vertical height of 24 km
• Not active
• Shield volcano
• Stayed over same hotspot

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Io is a moon about Jupiter

• Most volcanically active spot in the solar system
• Little gravitational pull and no atmosphere allow
  plumes to rise great distances

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Io
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Io
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What is used to predict the future eruption of a
volcano?

• Earthquake activity
• Change in chemical composition of the gases
  released by the volcano
• Change in the shape of the lava dome
• Change in volcanic activity of mountain

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• Unpredictability of eruptions
• People get used to/do not believe warnings
• No certain method for timely prediciton

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Long-term volcanic benefits

• Fertile soil
• Volcanic products
• Pumice
• Sulfur
• Diamonds
• Metamorphic ore

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The origin of Diamonds

• Diamonds form long, narrow cracks in the crust
  called pipes.
• These are similar to volcanic pipes, except there
  is no volcano above. Thefirst such pipe was
  discovered near Kimberley, South Africa, in 1867.
  The type of rock in the pipe was named kimberlite
  after the South African town. Since then,
  kimberlite pipes have been discovered in other
  areas, including Australia and Russia.
• Geologists think that diamonds form in the
  asthenosphere, where high temperatures and
  intense pressures cause pure carbon to
  crystallize.