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Have you ever looked inside a volcanic avalanche of hot rock and gas, and lived to tell the tale? No one ever has – until now.
Massey volcanologist, Dr Eric Breard, was one of over 500 graduates celebrating across three ceremonies in the Manawatū today. Dr Breard’s work focused on avalanches, known as pyroclastic flows, which are fast-moving clouds of hot rock and air that move down the flanks of volcanoes during volcanic eruptions.
These flows have been responsible for 50 per cent of volcano-related fatalities in the past two millenniums due to their extreme temperatures, typically of 100-800 degrees Celsius, and speeds of up to 600 km/h. The last notable example in New Zealand was during the 2012 eruption of Mt Tongariro. In the night of the 6 August 2012, the Upper Te Maari crater of Tongariro volcano generated pyroclastic density currents that travelled three kilometres and propagated across the Tongariro Alpine Crossing.
Breard describes the flows as one of the least understood of all volcanic phenomena. “I have been fascinated for six years by these currents because they are so hazardous and need to be fully understood to prevent future disasters,” he says. “It seems crazy to me that while we are planning to go to Mars in the next decades, on Earth the threat from pyroclastic density currents is very real and yet we cannot accurately predict their behaviour,” he says.
The inner workings of these flows have been a hotbed of debate between earth scientists, geophysicists, and applied mathematicians, each offering their own explanations of what may be occurring inside. Immeasurable in real-life, Dr Breard and his colleagues started synthesising the natural behaviour of these volcanic super-hazards in unique large-scale experiments, beginning in 2013.
This involved using Massey’s one-of-a-kind eruption simulator, which scales down all the physical properties of a large event so they can be safely observed and measured. The simulator is composed of a 13-metre high tower, where volcanic material is heated inside a hopper and released down a 12-metre channel, while high-speed cameras and sensors capture the data.
The experimental eruptions typically last 10 to 20 seconds only, but take about one month to prepare. The process involves getting the material near Taupo, drying it, building and callibrating the sensors and modifying the setup.
Dr Breard explains that the models are key to understanding how the flows move. “If the physics of these currents are not right in the models, we have no way to predict the runout and destruction potential of future pyroclastic density currents. There is no way to reduce the hazards of these currents, nor to alter them or stop them.
“Hence, the only thing we can do is predict their behaviour and make sure no-one will ever be in their path when they occur,” he says.
His research showed that a previously unknown gas-transport regime exists in experimental currents and controls their dynamics. Experimental results also revealed that the structure of dense currents differs in many aspects from the structure of classical gravity currents, which has fundamental implications for correct hazard modelling.
He will begin a postdoctoral fellowship at Georgia Institute of Technology next year.
Created: 25/11/2016 | Last updated: 25/11/2016
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