Volcanic hazards assessment
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VOLCANIC HAZARDS ASSESSMENT. Human-based Data Sources Geochemical Data Geophysical Data. ACTIVE vs. EXTINCT VOLCANOES. Historians say: Active volcanoes are those that are erupting or showing some activity now.

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VOLCANIC HAZARDS ASSESSMENT

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VOLCANIC HAZARDS ASSESSMENT

Human-based Data Sources

Geochemical Data

Geophysical Data


ACTIVE vs. EXTINCT VOLCANOES

  • Historians say:

  • Active volcanoes are those that are erupting or showing some activity now.

  • Volcanoes that have erupted historically, but are inactive at present, are Dormant.

  • Volcanoes that have had no activity in historical or archaeological time are Extinct.


ACTIVE vs. EXTINCT VOLCANOES

  • To geologists:

  • Active volcanoes have magma chambers

  • Extinct volcanoes have no magma left in chambers


HUMAN-BASED DATA

  • Historical Records

  • Archaeology

  • Oral Tradition

  • These can help extend the record back to a few thousand years


GEOCHEMICAL DATA

  • Radiometric Dates on Volcanic Materials-

    • Can extend dates back to millions of years

    • Give date of last eruption

    • Give repeat interval of past events

    • Show which types of volcanic products are expected


Geophysical Data are used to assess Present-day Risk

  • Is Magma Present? Determined by S-wave activity

  • Heat Flow, especially if increasing

  • Earthquake Patterns -shallow concentric patterns

  • Tilting or Bulge of Surface from GPS Data, Surveying, SAR Interferometry


Earthquakes in Hawaii


Earthquakes

In Iceland


Interferometry: Layering two Images of separate times on top of one another to measure vertical change

Top: visual spectrum shows nothing new

Bottom: Interferogram measures areas

of differential change due to ground

swelling upward. Maximum displacement

is in center and pattern is concentric,

suggesting a pending volcanic eruption


VOLCANOES IN THE US

There are 33 active volcanoes in the US

Most are at convergent plate boundaries in Alaska and N. California, Oregon, and Washington. These are all stratovolcanoes, which are the most dangerous in terms of explosive activity.

Some are on or near hotspots: Hawaii’s volcanoes, and Yellowstone

Some are former CPB: Central and Southern California

The remainder are on a failed rift (former divergent plate boundary): Arizona, New Mexico


VOLCANIC HAZARDS

  • Lava flows

  • Pyroclastics

  • Gases

    • Heated air

    • Toxic components

    • Climate change

  • Lahars

  • Tsunamis

  • Earthquakes


Volcanic Gases: 80% H2O, plus CO2, SO2, and also CO, H2S


GLOBAL COOLING DUE TO LARGE ERUPTION

Ash injected into

Stratosphere circulates

around the world

for up to 3 years


Lahar floods Armero, Colombiaafter eruption of Nevado del Ruiz


Krakatau, 1883

Lava and slope collapse produced a tsunami

up to 40m high.

-Killed 36,000 people in SE Asia

-Effects of Tsunami felt 7000 miles away

Ash and gases produced global cooling

that lasted 3 years


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