THE PROBLEM !!

NOT THE PROBLEM !!

VOLCANIC ASHVOLCANIC ASH • An unconsolidated mixture of sand to dust sized (1mm to .001 mm) rock and mineral fragments produced during explosive eruptions.

• Rock fragments are typically glassy and form as liquid magma quenches following its eruption at the earth’s surface

• Mineral fragments include plagioclase feldspar, hornblende, and pyroxene. These melt at higher temperatures than do the glassy rock fragments.

• Ash is hard, sharp, and angular.

VOLCANIC ASH !!

Frequency of Ash Cloud Frequency of Ash Cloud HazardHazard

• North Pacific volcanoes average 5-6 eruptions per year, with ash at flight levels on 4-5 days per year.

• On an additional 10-12 days per year, ash clouds are estimated to be close enough to flight routes to be a concern to aviation.

• Empirical estimates based on a combination of a 20-year record and a 200-year historical record (Miller and Casadevall, 2000)

• Extrapolation to the rest of the world shows that ash is expected to be at flight levels on 20-25 days per year, and a concern on 50-60 days per year.

BEZYMIANY VOLCANO JUNE 18, 2004