Háskóli Íslands

On Friday 15 August at 12:00, Dr. Samantha Engwell will give a talk in the IES lecture room (3rd floor in Askja):  "Dynamics and deposits of coignimbrite plumes"

Samantha Engwell conducted her undergraduate degree in Geology at the University of Edinburgh. She did an MSC by Research at Bristol, where her project focused on assessing lahar hazard at Galeras volcano, Colombia, using the TITAN2D numerical model. She stayed at Bristol to conduct her PhD with Steve Sparks and Willy Aspinall, in collaboration with Munich Re. to investigate uncertainties in the eruptive record of large explosive eruptions, particularly those related to tephra thickness measurements and volume estimates. Samantha is currently conducting a postdoc at INGV Pisa, as part of the NEMOH Marie Curie Training Network, where she is applying numerical modelling techniques to understand the formation of coignimbrite plumes. She is visiting Iceland on a NEMOH secondment to work with Sara Barsotti at IMO on the modelling of coignimbrite plume formation and dispersal using VOLCALPUFF.


Coignimbrite plumes form as material is elutriated from the top of pyroclastic density currents. The ash in these plumes is considerably finer grained than that in Plinian plumes and therefore can be distributed over large areas once in the atmosphere, with potentially disastrous consequences for aviation and health. To date, few coignimbrite deposits have been studied in detail, mainly due to their poor preservation potential, and difficulty identifying and distinguishing these deposits from Plinian deposits. As such, there is little in the published record regarding the physical characteristics of coignimbrite deposits. Analysis and interpretation of deposits from both the Campanian Ignimbrite (~39 kya) and May 18th 1980 Mount St. Helens eruptions highlight significant differences in the formation of coignimbrite compared to Plinian plumes. Such dynamical differences are investigated by coupling an ash flow model (Bursik and Woods 1996), with a column model (Bursik 2001) to identify key controls of coignimbrite plume formation, for example initial radius velocity and temperature. The results highlight the importance of correct identification of source conditions for modelling coignimbrite plumes and a requirement to treat such events separately to Plinian events.

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