Driving force of volcanic super-hazards uncovered

Source: Massey University

Associate Professor Gert Lube.

Massey volcanologists have discovered the driving force behind superheated gas-and-ash clouds from volcanic eruptions, which may help save lives and infrastructure around the globe. 

Endangering 500 million people worldwide, pyroclastic density currents (or pyroclastic flows) are the most common and lethal volcanic threat, causing 50 per cent of fatalities caused  by volcanic activity. During volcanic events, these currents transport hot mixtures of volcanic particles and gas over tens of kilometres, causing damage to infrastructure and loss of life.

One of the issues to studying these phenomena is that they are impossible to measure in real life. Using Massey’s Pyroclastic flow Eruption Large-scale Experiment (PELE) eruption simulator facility, the team were able to synthesize the natural behaviour of volcanic super-hazards and generate these flows as they occur in nature, but on a smaller scale.

Until now, scientists could not find the mechanism responsible for the super-mobility of these flows, and previous models were unable to accurately predict their velocity, runout and spread through hazard models, which put lives and infrastructure at risk. 

Massey University’s Associate Professor Gert Lube says that through their unique experiments, the enigmatic friction-cheating mechanism was found.

“With several tonnes of pumice and gas in motion, our large-scale eruption simulations uncovered the flow enigma that has been baffling researchers for decades. We measured a low-friction air cushion that is self-generated in these flows and perpetuates their motion. We were able to mathematically describe the resulting flow behavior. There is an internal process that counters granular friction, where air lubrication develops under high basal shear when air is locally forced downwards by reversed pressure gradients and displaces particles upward.

“This explains how the currents are able to propagate over slopes, bypass tortuous flow paths, and ignore rough substrates and flat and upsloping terrain, without slowing down.”

“The discovery necessitates a re-evaluation of global hazard mitigation strategies and models that aim to predict the velocity, runout and spreading of these flows. Discovery of this air-lubrication mechanism opens a new path towards reliable predictions of pyroclastic flow motion and the extreme runout potential of these lethal currents, thereby reducing future casualties. It will be used by hazard scientists, as well as decision makers, and is envisaged to lead to major revisions of volcanic hazard forecasts.”

The article, Generation of air lubrication within pyroclastic density currents, was published in Nature Geoscience.

Authors include Massey’s Professor Jim Jones, Dr Luke Fullard, Eric Breard and Joseph Dufek of the University of Oregon, Shane Cronin of University of Auckland and Ting Wang of the University of Otago. Funding includes Royal Society Te Apārangi Marsden Fund and the Ministry of Business, Innovation and Employment’s Endeavour Fund.


Workshop tackles international volcanic risks

Source: Massey University

An international group of volcanologists exploring New Zealand’s uniquie volcanic zone.

How accurately can we forecast the hazards and impacts of volcanic eruptions? How can we advance our computational modelling techniques to mitigate effectively against volcanic fatalities?

These were the questions volcanologists from across the globe were addressing, when they gathered in New Zealand in early January to debate and discuss the latest developments in volcanic hazard modelling, during the first international volcanic hazard benchmarking and validation exercise.

The International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) workshop was initiated and hosted by Associate Professor Gert Lube from Massey and his Physical Volcanology Group, thanks to a Marsden Fund grant.

It began with an official Māori welcome from Ngāti Tūwharetoa, with the first three days devoted to global volcano models. These were followed by field excursions to the Taupo caldera and Mt Ngauruhoe and Mt Tongariro, and a joint-eruption simulation at the Massey campus.

The main focus of the workshop was on pyroclastic flows – hot, fast-moving mixtures of particles and gas which form during volcanic eruptions and the most dangerous of volcanic phenomena. This was discussed in-depth during the workshop held at both the Tauhara Centre in Taupo and Massey’s Manawatū campus

Dr Lube says Massey is leading this area internationally through the University’s funded research programmes.

“The main objective of the workshop is the development of the international guidelines for modelling and mitigation of volcanic pyroclastic flow hazards. The international benchmark is a Massey-led initiative, in collaboration with American, and Italian volcanologists, to inter-compare, validate and advance existing and future hazard models globally,” he says.

“The workshop was attended by twenty of the global leaders in this field and assembled a mix of highly esteemed and emerging researchers. By establishing this workshop, we are now taking the next step to gather together experts to develop the work further and showcase Massey’s research to an international audience.”

Other objectives of the workshop included the advancement of novel volcano monitoring techniques between countries, facilitated through a joint large-scale eruption simulation at Massey where international researchers tested new sensor techniques, as well as identifying the future challenges in global volcanic hazard studies and strategic planning of large multi-national research programmes for the next 5-10 years to address these challenges. 

Safety around the world

Professor Michael Manga from the University of California, Berkeley, says the work is important for safety around the world.

“We would like to be able to predict where they [pyroclastic flows] go and their consequences, and to do so, we need models to help us make decisions. So, we are here to think about how to design better models, how to test those models. Validation and verification. There are two highlights. Personally, getting to see some of the most beautiful and amazing volcanic deposits is special. There’s nothing like seeing a real rock to understand how the earth works. Professionally, it’s the chance to work with some of my colleagues and see what’s going on here at Massey University,” he says.

“I think we have a vision that long-term we will forecast these flows and their consequences like we do the weather.”

Professor Greg Valentine from the University of Buffalo, New York, says, “We have got to the point now where everything we are doing in trying to understand volcanic eruptions is really inter-disciplinary, so it’s really necessary with people with expertise in different approaches and topics to talk together. This workshop has been really great for that.”

Attendees included Professor Michael Manga (University of California, Berkeley), Professor Joe Dufek (University of Oregon), Professor Greg Valentine (University of Buffalo), Professor Augusto Neri, Associate Professor Esposti-Ongaro and Dr Cerminara (INGV Pisa), Professor Roberto Sulpizio (University of Bari), Associate Professor Ulrich Küppers (University of Munich), Professor Gaku Ichihara and  Professor Takehiro Koyaguchi (University of Tokyo), Associate Professor Brittany Brand and Dr Nick Pollock (Boise State University), Dr Sanchez (University of Florence), Associate Professor Sylvain Charbonnier (University of Florida) and Associate Professor Olivier Roche (Universite Blaise-Pascal, Clermont-Ferrand).


Working with sand isn’t child’s play

Source: Massey University

Mustard seeds used in experiments around granular flow.

Ever wonder how an hour glass measures time? Who designed it, did the math, tested it and perfected it? Working with sand may sound like child’s play, but the process of understanding how these materials behave is the focus of scientists around the world – and it can mean big money and safer communities.

Granular materials, like sand, fascinate physicists, engineers, mathematicians, and other scientists. Granular materials include minerals, wheat grain, pharmaceutical powders, food powders, sugar grains, and seeds, adding up to multi-trillion-dollar enterprises. However they also include natural granular flows, like avalanches, landslides and more, with the understanding of their behaviour key to mitigating destruction from these natural events.

Massey’s Dr Luke Fullard is interested in both of these types, but his latest research looks into how these materials, like sand, behave in silos.

“The behaviour of gas and liquids in silos has been well studied and modelled, but there is a lot to be learnt about granular materials like sand – they are tricky as they can behave like solids, like liquids and even like gas. When you are trying to model the behaviour of granular particles, it is impossible to model every particle individually, so my research focuses on methods to treat flowing granular material like a continuous fluid.”

Changing the gap.

The physics of flow

The dynamics of granular flow from a silo with two symmetric openings, was published in the Royal Society journal Proceedings, describes the behaviour of sand draining out of a silo.

This project involved developing mathematical models followed by lab experiments in silos help to understand the physics of the flow and to generate data to validate the mathematical models. In these models, the distance between the two openings was studied in how it changes the flow rate.

They found that the flow rate is highly dependent on the spacing between the two openings with a complicated interference behaviour between the two openings – make them too wide or two narrow and the flow rate changes.  

“These results aid understanding of granular physics, particularly granular interference phenomena. The results may also have implications for industrial silo design, giving valuable information for how grains or powder behaviour when being processed.”

Dr Luke Fullard with the small-scale model.


Bird bone streaming

Source: Massey University

3D digitised skull of a little bush moa from Auckland War Memorial museum.

A new website for viewing 3D bird bones aims to make bird bones in museums more accessible for research and teaching.

Massey University senior lecturer Dr Daniel Thomas has launched a new website, called Fauna Toolkit: Bird Bones for students and researchers interested in identifying bird bones.

Inspired by existing initiatives like Aves3D.org, the site currently contains 159 bones from 28 species, including many New Zealand species, such as the Little Bush Moa, the North Island Brown Kiwi, and Kārearea (New Zealand falcon), and Dr Thomas plans to add more items.

Dr Thomas says the project is designed around the philosophy of making objects that are not on display in museums, more easily available.

“Museum collections are often rich with local species and may have fewer specimens from overseas, meaning that researchers may need to travel internationally if they want to view bones from certain birds. A project like this one can make bones of rare species potentially accessible anywhere.”

The digitised models were created by scanning collections belonging to the Auckland War Memorial Museum and Canterbury Museum.

Dr Thomas intends to use this site for his own research and teaching, including the bones module of the 300-level Ornithology class he teaches.

“Imagine walking along a beach and discovering a bird bone recently exposed out of a sand dune” says Dr Thomas. We can use the 3D models to identify where in the body the bone is from, and we could maybe use the models to identify the species.”

“Paul Scofield from Canterbury Museum first encouraged me to launch the website and Guy Annan at Auckland Museum guided the site’s design. We look forward to continuing to grow the site in the future.”