6 FALL3D is a 3-D time-dependent Eulerian model for the transport and deposition of 7 volcanic ash. The model solves the advection-diffusion-sedimentation (ADS) equa8 tion on a structured terrain-following grid using a second-order Finite Differences 9 (FD) explicit scheme. Different parameterizations for the eddy diffusivity tensor 10 and for the particle terminal settling velocities can be us...

INTRODUCTION The use of satellite techniques provides valuable information for mapping ash hazards, as well as the means to study and predict the fates of volcanic clouds. We have used ultraviolet (TOMS – Total Ozone Mapping Spectrometer) and infrared (e.g., AVHRR – Advanced Very High Resolution Radiometer; HIRS2 – High Resolution Infrared Radiation Sounder/2; GOES – Geostationary Operational E...

[1] Sintering and densification are ubiquitous processes influencing the emplacement of both effusive and explosive products of volcanic eruptions. Here we sinter ash-size fragments of a synthetic National Institute of Standards and Technology viscosity standard glass at temperatures at which the resultant melt has a viscosity of ∼108-109 Pa.s at 1bar to assess sintering dynamics under near-sur...

A major source of error in forecasting where airborne volcanic ash will travel and land is the wind pattern above and around the volcano. GNS Science, in conjunction with MetService, is seeking to move its routine ash forecasts from using the ASHFALL program, which cannot allow for horizontal variations in the wind pattern, to HYSPLIT, which uses a full 4-D atmospheric model. This has required ...

There has been an increasing interest in the effects of volcanic eruption on the environment, climate, and health following two recent volcanic eruptions in Iceland. Although health issues are mainly focused on subjects living close to the eruption due to the high concentration of airborne ash and gasses in close vicinity to the volcanoes, the ash may also reach high altitude and get distribute...

Wind erosion of freshly-deposited volcanic ash causes persistent storms, strongly affecting ecosystems and human activity. Wind erosion of the volcanic ash was measured up to 17 months after the ash deposition, at 7 sites located within the ash-deposition area. The mass flux was measured up to 1.5 m above ground level. Mass transport rates were over 125 times the soil wind-erosion rates observe...

Volcanic eruptions can generate widespread deposits of ash that are subsequently subjected to erosive forces which causes detrimental effects on ecosystems. We measured wind erosion of the freshly deposited Eyjafjallajökull ash at a field site the first summer after the 2010 eruption. Over 30 wind erosion events occurred (June-October) at wind speeds > 10 m s(-1) in each storm with gusts up to ...

Cristobalite is a common mineral in volcanic ash produced from dome-forming eruptions. Assessment of the respiratory hazard posed by volcanic ash requires understanding the nature of the cristobalite it contains. Volcanic cristobalite contains coupled substitutions of Al3+ and Na+ for Si4+; similar co-substitutions in synthetic cristobalite are known to modify the crystal structure, affecting t...

We report the discovery of numerous in situ Miocene and Pliocene airfall volcanic ashes that occur within the hyperarid Dry Valleys region of the Transantarctic Mountains in southern Victoria Land, Antarctica. Ashes that occur above 1000 m elevation rest at the ground surface, covered only by a thin ventifact pavement 1 to 2 cm thick. The ash deposits are loose and unconsolidated and show no si...

Satellite measurements of volcanic sulfur dioxide (SO2) emissions can provide critical information for aviation hazard mitigation, particularly when ash detection techniques fail. Recent developments in space-based SO2 monitoring are discussed, focusing on daily, global ultraviolet (UV) measurements by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. OMI’s high sensitivity to SO2...