Producing a big explosion means a good day at work for Associate Professor Gert Lube of Massey University’s Institute of Agriculture and Environment. ‘I am fascinated by studying volcanic eruptions, particularly the most explosive and dangerous,’ he says.
‘I’m interested in the processes that produce pyroclastic flows — red-hot glowing avalanches of pumice, volcanic ash and gas that race down from volcanoes to devastate everything in their path. I am also interested in understanding volcanic mud flows or lahars, like the ones that occur from Ruapehu. They are quite beautiful processes but they are also extremely dangerous.’
New Zealand has many active volcanoes, with White Island, Tongariro and Ruapehu erupting regularly in geological terms. Our other volcanoes erupt less frequently, but given their location (such as those in the Auckland volcanic field), or their propensity to produce huge eruptions (such as Taupō), their potential for damage is enormous.
As a volcanologist, Associate Professor Lube feels a strong sense of duty to better understand the processes involved in our volcanoes, so that we might more accurately predict eruptions and react in the best way possible. The trouble is, taking measurements during eruptions is extremely difficult. ‘We can only measure so much when it comes to real explosions, because of the enormous energies, forces and temperatures involved.’
His solution is to construct a volcano simulator, a 14-metre-tall apparatus that heats natural pumice and ash to produce scaled eruptions. Named Pele after the Hawaiian goddess of volcanoes, the simulator allows pyroclastic flows to be measured as they occur, but in relative safety. ‘It’s a fascinating thing for us to do and it attracts a large number of overseas scientists to come here and to learn with us,’ Associate Professor Lube says.
‘We are trying to understand the mathematics and physics of eruptions because these are the main ingredients that go into computational hazard models. It’s not easy because volcanic eruptions aren’t only dangerous and beautiful, but they also involve some of the most complicated physical processes and they go close to the limit of where our current knowledge in physics is. They have a very large range of energy scales, and they involve high temperatures and hot gas and particles. Whenever you have these elements working together at high energy and high turbulence, a diversity of processes occurs at the same time. Here, our current theories in physics begin to break down. Our main focus is to improve the physics, with a view to protecting human life and primary infrastructure in New Zealand and in other areas where there are volcanoes worldwide.’
Our main focus is to improve the physics, with a view to protecting human life and primary infrastructure in New Zealand and in other areas where there are volcanoes worldwide.
ASSOCIATE PROFESSOR GERT LUBE
Having good models of our own volcanoes is a relatively new phenomenon, Associate Professor Lube explains. ‘We used to just run existing models from overseas, and we see that these are not good enough because they have been calibrated for overseas volcanoes, and we just can’t use these results to make safe predictions for our volcanoes.’
With colleagues from Victoria University, Associate Professor Lube has recently begun a new project looking at the rare but extremely powerful phenomenon known as ‘supervolcano’ eruptions. New Zealand has the largest number and the most active supervolcanoes worldwide, located between Taupō and Rotorua. ‘There is something like one hundred to one thousand cubic kilometres of magma sitting beneath Taupō at the moment, and that is becoming more dangerous the longer it sits there. Every few decades, that magma becomes disturbed, and we see this as earthquakes, increased thermal activity and sometimes lake level changes. Every few hundred years, Taupō erupts, as do the volcanoes around Rotorua, like Tarawera. As volcanologists, we mostly concentrate on recently erupting volcanoes, because we understand them very well, but not much is known about how supervolcanoes erupt and so that is what we will look at over the next five years.’
As well as his research, Associate Professor Lube and his students facilitate the national eruption warning systems. ‘If volcanoes were to erupt, we would immediately respond. We have monitoring equipment at the volcanoes, and we work together with the national monitoring organisation unit. I also work with the science advisor for the Ministry of Civil Defence and Emergency Management. Immediately after the onset of an eruption everyone would want to know how big it is going to be, where it would impact, whether evacuations are needed, and how long it is going to last. These are the main big questions, but they are the hardest ones to answer for volcanologists.’