Between a Rock and a Hard Place


Lakes and lahars at Mt Ruapehu

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.

Alumnus profile #6 – Dr Sam Engwell

DSC_0500Dr Sam Engwell

Marie Curie Early Stage Researcher, INGV

PhD title “Dynamics and Deposits of Large Explosive Eruptions”



1) The Twitter Challenge: Describe your PhD in 140 characters

Investigation of eruption processes during supereruptions by analysis of deposits in deep-sea sediments.

Deep sea core

Deposits from the Campanian Ignimbrite eruption can be found over 1000km away from the eruption source in deep sea cores. Photo credit: Sam Engwell

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Phreatic eruptions – the silent assasins


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.

Review of the BGS myVolcano iPhone app

A few months ago, Elspeth posted a review of her top geology-themed mobile phone apps. Since then, the resourceful folk at the British Geological Survey (BGS) have come up with a new contender; here we take a look at myVolcano.


Any self-respecting app needs a jazzy icon. Photo credit: myVolcano/British Geological Survey

Before we get started, the important details: myVolcano is free to download but is only currently available on Apple’s iOS (an Android version is in the pipeline). You can download it here.

The main driver behind the app is to allow the BGS to collect data about volcanic hazards through observations made by the general public. This concept is known as citizen science, and is becoming increasingly useful to researchers. For example, the USGS and the BGS have webpages where anybody can submit details if they experience an earth tremor; the results are then made openly available as ‘Felt location maps’. In the same way, myVolcano is built to allow you to submit observations about volcanic hazards and ashfall.


Screenshots of the myVolcano interface on iOS 7. Photo credit: Charly Stamper/British Geological Survey

The app interface itself is refreshingly sleek and intuitive to use. All the app’s features centre around a map that is populated with entries from the Smithsonian Institution Global Volcanism Program databse. That’s a huge amount of data (1,550 volcanoes and 10,000 years of eruptions, to be precise) made freely available at your fingertips. Each volcano entry features a geological background, details of the last known eruption and a photo.


Screenshots from the myVolcano app. From L-R: Excellent demonstration of the ‘Ring of Fire’; example of a database entry; example of a user submitted observation. Photo credit: Charly Stamper/British Geological Survey

Now, for those of us living in the UK, the chances of us witnessing volcanic phenomena at home are pretty rare; however, it is not uncommon for ash particles from distant eruptions to settle on our shores (e.g., ashfall from Eyjafjallajökull, 2010, was recorded as far south as the Midlands). Data from such distal deposits can be used by geologists to help understand how ash plumes travel and disperse. myVolcano talks you through how to submit measurements and photos of just such an ash fall. This record is then plotted on the world map using the GPS on your phone and can be viewed by other users of the app.

In truth, it’s worth downloading this app purely to access the Smithsonian database on your phone. Whether the citizen science aspect of myVolcano really takes off remains to be seen…where’s that simmering Icelandic volcano when you need it?