Volcanic Hazards

1
Volcanic Hazards
Lava flow
Lahar
Landslides
Ash fall
Pyroclastic flow
2
Volcanic Hazards
3
Mt. St. Helens before the 1980 eruption
Bulge plug that is pushed out by magma within
the conduit.
4

• Pyroclastic eruption
• Mt. St. Helens
• Landslide
• Release of pressure
• Lateral blast
• Pyroclastic flow- down with the pull of gravity
• Ash cloud-vertical
• Ash fall

5
Landslide

• Gravitational force pulls unstable material
  down slope
• Fills canyons and valleys with debris

6
Landslide, Mt. Shasta

• 300,000 years ago
• 20 times more material than the Mt. St. Helens
  landslide

7
Lateral Blast extreme pyroclastic flow

• In the case of Mt. St. Helens, the landslide
  uncorked the vent.
• Gas and debris were released under tremendous
  force
• Burns and destroys anything in its path

8
Lateral Blast

• Large area completely devastated (23 X19 miles)
• Trees knocked down
• Vegetation burned off

9
Mt. Unzen, Japan

• Geologists examined volcanoes all around the
  world.
• Mt. Unzen, Japan and Mt. Hood, Washington have
  the potential for lateral eruptions.

10
Pyroclastic flow hot gas propels pyroclastic
debris

• Montserrat, 1997

• Gravitational force pulls hot gas and pyroclastic
  debris down slope from the initial vertical
  eruption.

11
Pyroclastic Flow

• Mt. Pinatubo, Philippines
• 1991
• May reach 100 miles per hour
• Burns or suffocates anything in its path

12
Vertical Eruptions Plinian

• If the initial eruption is vertical the force
  sends debris into the stratosphere

13
Global cooling debris blocks sunlight
14
Mt. Pinatubo
Major eruptions blocking Suns radiation
Cooled global temperatures by .5-.6 degrees
Centigrade
15
Volcanism

• 1815- Large eruption in the tropics once thought
  to be Tambora in Indonesia
• Global temperatures fell
• Crops failed throughout Europe and famine spread
• Mary Shelly told her house guests the story of
  Frankenstein and his creator died in the arctic
  because they were unable to go outside during
  their vacation

16
Ash fall
Photomicrograph of ash from the Mt. Tehama
eruption (Lassen Peak)

• Acts as an abrasive
• Clogs machinery, covers vegetation, irritates
  lungs and eyes

Ash deposited associated with the eruption of the
Long Valley Caldera
17
Iceland

• Located on the North Atlantic mid-oceanic ridge
• Hot spot
• What type of lava?
• Viscosity?
• Eruptive style?

18
Iceland's Eyjafjallajokull volcano

• Volcanic eruption under ice produces steam and
  other gases to propel pyroclastic debris into the
  atmosphere
• European air travel was interrupted for weeks

19
Mt. Yasur, May 30, 2010

• Some flights rerouted or cancelled in Australia

20
Volume of Pyroclastic Debris
Ash
21
Lahars

• Remobilized ash, rock and debris by water
• Water source needed rain, snow melt

22
Mt. St. Helens
23
Mt. Rainier lahars from the last 5600 years
24
Lahars Mt. Pinatubo
25
Lava Flow

• Destroys everything in path
• People and animals can usually escape

26
Iceland The Eldfell volcano on the island of
Heimaey

• New land was created during the 1973 eruption.

27
Jokulhlaup

• One third of country is covered by active
  volcanoes
• About 13 covered by glaciers
• The lava melts the ice cap
• At one point the large volume of water pours
  rapidly to the adjacent area

28
Gas Emissions

• Sometimes gas release is concentrated and toxic
  to vegetation and people

Horseshoe Lake near Mammoth, California
29
Carbon dioxide leaked out of Lake Nyos, Africa
suffocating 1700 people and all animal life.
30
(No Transcript)
31
Understanding Volcanic Hazards

• Past history
• How often
• Types of hazards
• Extent of hazards
• Location of past events

Ash deposits associated with the eruption of
Santorini, Greece