VOLCANIC HAZARDS ASSESSMENT Human-based Data Sources Geochemical Data Geophysical Data

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  • VOLCANIC HAZARDS ASSESSMENT

    Human-based Data Sources

    Geochemical Data

    Geophysical Data

  • ACTIVE vs. EXTINCT VOLCANOESHistorians 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 VOLCANOESTo geologists:

    Active volcanoes have magma chambers

    Extinct volcanoes have no magma left in chambers

  • HUMAN-BASED DATAHistorical RecordsArchaeologyOral Tradition

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

  • GEOCHEMICAL DATARadiometric Dates on Volcanic Materials-

    Can extend dates back to millions of yearsGive date of last eruptionGive repeat interval of past eventsShow which types of volcanic products are expected

  • Geophysical Data are used to assess Present-day Risk

    Is Magma Present? Determined by S-wave activityHeat Flow, especially if increasingEarthquake Patterns -shallow concentric patternsTilting or Bulge of Surface from GPS Data, Surveying, SAR Interferometry

  • Earthquakes in Hawaii

  • EarthquakesIn Iceland

  • Interferometry: Layering two Images of separate times on top of one another to measure vertical changeTop: visual spectrum shows nothing new

    Bottom: Interferogram measures areasof differential change due to groundswelling upward. Maximum displacementis in center and pattern is concentric,suggesting a pending volcanic eruption

  • VOLCANOES IN THE USThere 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: Hawaiis 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 HAZARDSLava flowsPyroclasticsGasesHeated airToxic componentsClimate changeLaharsTsunamisEarthquakes

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

  • GLOBAL COOLING DUE TO LARGE ERUPTIONAsh injected into Stratosphere circulatesaround 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