Why Some Volcanic Eruptions Produce Ash Clouds and Others Don’t

June 4, 2010

Volcanoes exist in many parts of the world, and their eruptions can be terrifying and devastating, as Aon Benfield’s Professor Russell Blong discusses in the previous article at: https://www.insurancejournal.com/news/international/2010/06/04/110441.htm.

However, not all volcanic eruptions produce clouds of gritty ash that threaten airplane engines and ground flights, causing billions of dollars in economic losses to airlines. Kilauea in Hawaii has been erupting for years without notably disturbing flights to and from the islands.

The IJ contacted Prof. Blong, and asked him for an explanation of the differences. In an e-mail he noted the following points:

“The Icelandic eruption produced a lot of fine ash because a lot of ice/water was involved – explosive fragmentation of the erupted material resulting from contact with chilled water/ice. This means that the ash can travel a lot further in the atmosphere.

“Transport distance is a function of the height to which the initial explosion is lofted as surrounding air is entrained into the rising cloud, and by particle mass, wind speed in the surrounding atmosphere, etc.

“I’m not sure which of the various factors is the most important but energy of the explosion, eruption mass and particle size/mass are probably the important ones.

“The second point is that encounters between planes and ash are not uncommon. The Darwin (Australia) Volcanic Ash Advisory Centre recorded around 30 ash encounters between 1979 and 2001 and I assume there have been many more since.

There is not a lot that is new, it seems to me, in the recent Icelandic episode, except the magnitude of the consequences, no doubt contributed to by globalisation, mass air travel etc. One of the most interesting questions might be – why have we failed to build on the understanding that was around by 1990?”

Bill McGuire, his colleague at Aon Benfield added:
“Two important points are (1) that the potential threat of Icelandic ash to aviation has been known and flagged-up for decades. It was certainly recognized within the aviation community, or at least elements of it.

“(2) The problem in April and May arose primarily because – despite more than 30 years of jet aircraft encounters with ash clouds – the aviation community had still not got itself sufficiently organized to tackle the issue of safe flying in dilute ash clouds remote from their sources.

This left ‘avoid at all costs’ as the only protocol in place and – consequently – the unavoidable closure of UK and European airspace.”

Emeritus Professor Russell Blong, currently a consultant to Aon Benfield, “founded the insurance industry-funded Macquarie University (Sydney) research group Risk Frontiers – Natural Hazards Research Centre in 1994. He retired as Director of Risk Frontiers in 2003. He has researched a wide range of natural hazards and their consequences for nearly 40 years,” Aon stated.

“His particular interests lie in integrated multi-criteria natural hazards risk assessment, loss modeling, building damage analysis and risk reduction for a wide range of natural perils in the Asia-Pacific region.

His books include Volcanic Hazards: A Sourcebook on the Effects of Eruptions, and Natural Perils in Australia and New Zealand.

Was this article valuable?

Here are more articles you may enjoy.