Volcanic Hazards

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Volcanic Hazards Primary Effects -lava
flows -pyroclastic eruptions -poisonous gas
emissions Secondary Effects -mudflows and
debris avalanches -flooding (glacial outburst
floods) -tsunamis -seismicity -atmospheric
effects and climate change Volcanic Hazards along
the Cascadia Subduction Zone Predicting
Eruptions Monitoring the Movement of Magma
-seismic studies -magnetic field
changes -electrical resistivity Physical
Anomalies and Precursor Phenomena -ground
deformation -change in heat output -change in
the composition of gases -local seismic activity
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Basaltic eruptions are very fluid and will flow
great distances from the vent or rift. The photo
above is taken from the Kilauea rift zone on the
Big Island of Hawaii.
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Aa Flow, Hawaii
Pahoehoe Flow, Hawaii
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Few fatalities are typically associated with
basaltic lava eruptions, as neighborhoods, such
as the one shown here, can be evacuated.
Buildings and other human-made structures are not
so lucky!
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Basaltic lava flow reaching a neighborhood near
Kilauea, Hawaii.
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Lava flow induced fire, Hawaii.
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Pyroclastic eruptions and flows produce some of
most devastating effects associated with
volcanism. Destruction is total to any living
organism or structure within the pathway of a
pyroclastic flow.
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Landslide north face of Mt. St. Helens May 18,
1980.
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Mt. St. Helens May 18, 1980
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Mount St. Helens Pyroclastic flow May 18, 1980.
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Bishop ash was erupted catastrophically 760,000
years ago in eastern California. The eruption
had a VEI 7 and ashfall accumulated as far
Nebraska.
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Pompeii, Italy 79AD
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Volcanic Hazards Primary Effects -lava
flows -pyroclastic eruptions -poisonous gas
emissions Secondary Effects -mudflows and
debris avalanches -flooding (glacial outburst
floods) -tsunamis -seismicity -atmospheric
effects and climate change Volcanic Hazards along
the Cascadia Subduction Zone Predicting
Eruptions Monitoring the Movement of Magma
-seismic studies -magnetic field
changes -electrical resistivity Physical
Anomalies and Precursor Phenomena -ground
deformation -change in heat output -change in
the composition of gases -local seismic activity
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Causal Factors for Lahar Flows
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Lahar flow from Mt. Pinotubo.
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Volcanic tephras are well-preserved in lacustrine
and bog sediment throughout the Cascades.
Ubiquitous organic matter provides excellent
opportunities to assign radiocarbon ages to the
eruptions. The Mt. Mazam O (Crater Lake)
eruption occurred 6800 years ago.
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Excavating a trench behind the Hyak moraine at
Snoqualmie Pass (ca. 1990).
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Mt. St. Helens Wn
Mt. St. Helens Yn

• Mazama O

Three tephra layers are presnt in the sediment
record at Snoqualmie Pass. They have been
independently dated using radiocarbon dating of
associated organics.
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Tephra distribution from Mt. Mazama, Longvalley
and Yellowstone eruptions.
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• Tephra distribution of Cascade volcanoes

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• Isopachs of Glacier Peak tephra distribution
  (13,100 yr BP).

Isopachs of Glacier Peak tephra distribution
(13,100 yr BP).
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Mt. Rainiers elevation exceeded 16,000 feet
above sea level 5000 years ago.
Following a large edifice collapse 5000 years
ago the mountain lost 1500 feet of its summit.
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Mt. Rainier contain 90 of the Cascades glacial
ice and permanent snow.
Mt. Rainiers glacial ice is a major potential
source
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Oceola Lahar (5200 yr BP) near Enumclaw, WA.
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Glacier Peak has been active Cascade volcano over
the past 15,000 years.
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Unconsolidated pyroclastic deposits on north face
of Mt. St. Helens source of lahar flows.
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Reworked pyroclastics incorporated into Mt. St.
Helens lahar deposits.
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Volcanic Hazards Primary Effects -lava
flows -pyroclastic eruptions -poisonous gas
emissions Secondary Effects -mudflows and
debris avalanches -flooding (glacial outburst
floods) -tsunamis -seismicity -atmospheric
effects and climate change Volcanic Hazards along
the Cascadia Subduction Zone Predicting
Eruptions Monitoring the Movement of Magma
-seismic studies -magnetic field
changes -electrical resistivity Physical
Anomalies and Precursor Phenomena -ground
deformation -change in heat output -change in
the composition of gases -local seismic activity
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• Can we predict volcanic eruptions?
• Yes, but with caveats!!!
• Requires a thorough understanding of the
  volcanos eruptive history.
• Requires appropriate instrumentation on the
  volcano well in advance of the eruption.
• Requires constant monitoring of instrumentation
  so that incoming data can be properly
  interpreted.
• The science behind predicting volcanoes has
  improved substantially over the past decades, but
  volcanologists can only provide probabilities
  regarding the timing of a given eruption. It is
  not possible to determine the exact severity of
  an eruption or whether the magma will even reach
  the surface.

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• How do volcanoloists predict volcanic eruptions?
• Monitor seismic data related to movement of
  magma.
• Monitor ground deformation and dome expansion.
• Monitor volcanic gases emitted as magma rises and
  expanding gases are released.

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• Successful Volcanic Predictions
• Volcanologists predicted the eminencne 1980 Mt.
  St. Helens eruption. Their warnings of an
  impending blow prompted the U.S. Forest Service
  to evacuate people from dangerous areas near the
  volcano. Although 57 people died in the eruption,
  it is estimated that as many as 20,000 lives were
  saved.
• In the spring of 1991, a USGS SWAT team was
  rushed to the Philippines' Mt. Pinatubo and
  successfully predicted the June eruption, leading
  to evacuations that saved thousands if not tens
  of thousands of lives and millions of dollars
  worth of military equipment at the nearby Clark
  Air Force Base.