Between a Rock and a Hard Place

Lakes and lahars at Mt Ruapehu

Charly Stamper October 23, 2014

Mt Ruapehu is the largest mountain on the North Island of New Zealand. As well as being a popular ski resort, Ruapehu is an active andesitic stratovolcano. Formed approximately 200,000 years ago, activity is currently confined to the Crater Lake vent; this deep depression fills with water from snow melt between eruptive episodes.

Skiing on Mt Ruapehu, North Island, New Zealand. Photo credit: Airflore

Skiing on Mt Ruapehu, North Island, New Zealand. The name ‘Ruapehu’ is Māori for ‘exploding pit’. Photo credit: Airflore

Similarly to the recent eruption of Mount Ontake in Japan, Ruapehu has been known to erupt without warning. In September 2007, the volcano produced a sudden blast of steam and debris in a minor phreatic eruption, trapping two climbers who were near the vent at the time and generating mud and ice slurries from the resultant meltwater.

On this snow-capped peak, the biggest threat to skiers from such unexpected phreatic events is the production of large lahars by collapse of Crater Lake. Understandably, GNS (the country’s geological survey) have taken a number of measures to try and protect the tourists that flock to Ruapehu during the ski season.

The volcano is monitored using 2 web cameras, 10 seismographs, 6 microphones and 9 continuous GPS stations. The temperature of Crater Lake is regularly measured, and GNS conduct airborne gas surveys. Most importantly for skiers, the eastern flanks of the volcano are guarded by ERLAWS, a lahar warning system which gives skiers up to five minutes warning of an impending lahar.

Yet, notwithstanding this battery of monitoring equipment, we should remember that Ruapehu has the potential to catch us all by surprise.

Science Snap (#33): Earth Science Week

Elspeth Robertson October 17, 2014

James Hickey is a PhD student in the School of Earth Sciences at the University of Bristol. A geophysicist and volcanologist by trade, his PhD project is focussed on attempting to place constraints on volcanic unrest using integrated geodetic modelling.

Earth Science Week is an international initiative to promote the great work that goes on in the geoscience community. It encompasses a huge range of topics; from dinosaurs to glaciers, and volcanoes to meteorites. There’s something for everybody. For an overview of how geoscience can have a positive influence on local communities and save lives, check out this video from the AGU:

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For Earth Science Week, events are taking place here in the UK, organised by the Geological Society, as well as across the Atlantic in the US, where the American Geosciences Institute are coordinating things. To get an idea of the sorts of activities that are happening and see where you can get involved, you can check out their websites here and here.

So far my favourite initiative has been the release of the 100 top ‘Geosites’ in the UK. This list, compiled by the Geological Society and voted on by members of the general public, represents the best the UK has to offer in various geological categories (e.g. landscapes, adventurous, educational, and so on). You can view the ‘Geosites’ in an interactive map, and there are some great pictures to flick through in a BBC News article.

Seemingly precariously balanced, these are the Brimham rocks in North Yorkshire, part of the top 100 ‘Geosites’ in the UK. Image credit: BBC News.

Science snap (#32): Coral currents

Elspeth Robertson October 16, 2014

KT Cooper is a PhD student in the School of Earth Sciences at the University of Bristol. A carbonate geochemist by training, here she dives into the world of corals.

Coral is misunderstood. It may look like a beautiful underwater plant, and for a long time it was thought to be one, but is in fact an invertebrate. The coral structures are colonies made up of individual small polyps. These produce an exoskeleton made up of calcium carbonate, which helps to preserve them in life and also in the fossil record.

Another misunderstanding about corals is that, on the whole, they are passive creatures obtaining their nutrients from the ambient flow of the oceans. Recent research at MIT and the Weismann Institute of Science (WIS) suggests otherwise. They have found that the external cilia (small threadlike appendages similar to those found inside a human lung) of the coral generate eddy currents which draw nutrients to, and potentially waste produce away, from the colonies. Using powerful microscopes and high-speed video equipment they have managed to capture this unexpected behavior on film.

Eddy currents being generated by external cilia of coral. The paths of the tracer particles are colour-coded by fluid velocity. Image courtesy of MIT and the researchers

This research maybe an insight into how these tiny creatures have managed to survive, and thrive, so efficiently in the changing ocean environments as well as allowing scientists to visualize cilia-related processes that occur hidden from view inside organisms.

Phreatic eruptions – the silent assasins

Charly Stamper October 7, 2014

Mt Ontake, Japan, in a more placid mood.
Photo credit: Tetusya Kanakubo

The recent eruption of Mt Ontake, Japan tragically killed at least 50 hikers who were on the volcano at the time. Within hours of the eruption taking place, social media was flooded with first-hand video footage illustrating just how close many survivors came to perishing in an onrushing pyroclastic flow.

Despite having a sophisticated seismic and geodetic monitoring system, many news reports stated that Ontake erupted seemingly without warning. Based on the evidence available at this time, it is probable that the event at Ontake was phreatic.

Phreatic eruptions occur when water enters a magmatic system and is heated to form steam. As these volcanic events do not involve the movement of magma, they are not accompanied by any of the normal eruption precursors such as ground inflation, seismic swarms or increased gaseous emissions.

As the Ontake hikers found out, a volcano which can erupt without warning is a pretty dangerous prospect.