Unzen fieldwork: Guest post by Becky Coats

This is a guest post by Becky Coats, a volcanology postgraduate here at the University of Liverpool. She has written about her amazing recent fieldwork to Unzen volcano in Japan!  

Meet the A Team: Mission Unzen-Fugen, feat. (left to right, top to bottom) Claire Harnett, Paul Wallace, Dr. Mark Thomas, Dr. Takahiro Miwa, James Ashworth, Dr. Jackie Kendrick, Prof. Yan Lavallée, and me!

This trip was a collaboration between the University of Liverpool (Jackie, Yan, Paul, James and myself), the University of Leeds (Mark and Claire) and the National Research Institute for Earth Science and Disaster Prevention, Japan (Taka). Those of us from UK universities were in Japan from the 8th to the 20th of May and were granted permission for 6 days work on the lava dome each armed with our own specialist tasks but with one collaborative question: How stable is the dome today?

My assignment was to collect samples from a near by pyroclastic deposit that represent the range of material (from dense to porous) that was emplaced during the Heisei eruption (Nov. 1990 - Feb. 1995), These are large (~15 kg) rocks that I have taken back to the lab in Liverpool to carry out strength tests upon, one of them is in my bag in picture above!!

On the days not reserved for dome work we went to Geopark sites, special locations designated by the Japanese Governments as places of geological interest. The site shown here is where debris flows inundated many houses, disrupting the lives of many Japanese people. The government have preserved several of these houses in order for future generations to visit.

Ono-koba Elementary School in Fukae Town was overwhelmed by pyroclastic density currents and burned through in September 1991. Luckily all the students were evacuated and thus there were no casualties, however earlier that year in June a previous pyroclastic flow came close to reaching the school with the students still inside. The building still stands preserved as a historical reminder of the pyroclastic disaster. What I love about Japan is that not one part of the school is vandalised, only a small fence stands between viewer and building for the safety of the public and yet there are no signs of entry. The respect the Japanese population has for these sites is inspiring.

Day one on the dome, dishevelment hasn’t reached me quite yet and although I don’t look it, I am very excited. This is what one could only refer to as the arse of the spine.. teeming with an almost odourless gas from fumaroles this spot is the most photogenic outcrop of the whole dome. So understandably EVERYONE (who makes it) has their picture taken in front of this, here’s mine. There is a slight risk of rock collapse on the dome due to frequent earthquakes in the area so safety is paramount, and the reason why the dome isn’t open to the public. The recent Kumamoto Earthquakes have changed the morphology of the dome slightly since the previous visit of my colleagues. We have to make sure we are equipped with hard hats, gloves and lots of water.

The incredible view of the Shimabara peninsula while we overlook lobe 11. The Heisei dome-forming eruption of Mt. Unzen was built up in stages, creating 13 lava lobes, but not every lobe is preserved due to total or partial collapse. Lobe 11 is the largest of these and is split into an a and b sections. In this photograph we are looking approximately East, bearings are difficult to obtain on the dome however due its composition (dacite lava) having a high magnetic signature, i.e. it messes up your compass big time. Typically at this serene moment Prof Lavallée is more interested in taking pictures of the rocks.

Dr. Jackie Kendrick and I after our third day in a row descending the dome. We are rather pleased with ourselves as it is quite an achievement to have made it this far, plus we know that the next two days bring rain and thus will not involve any more climbing. The view of the dome from this angle is rather beautiful I think, you can see the spine just poking out from the top.

A little bit of culture, we were very lucky to get to stay in a very beautiful hotel during our work on the dome. Pretty much all of the hotels in Unzen village have thermal pools (onzens – bottom middle picture) that are perfect to rest your tired muscles in. These are both communal and private (if you book in advance) and every morning we would book our own private onzen to take away the muscle aches of the days work. These baths are filled with water from the local fumarole network (top middle picture). After our onzen we would have an amazing meal prepared for us by the chefs in the hotel full of traditional foods. The picture on the right is a live shell fish with some butter, the fuel below the dish is turned on and after five minutes the fish is turned and is doused in sake and allowed to cook for another five. Creepy but delicious. The picture on the left is our tatami area in our hotel room where you can sit in your yukata and have some complimentary green tea. This is luxury to the normal camping scene we have during fieldwork, another reason I love Japan.

Some great examples of teamwork on the dome and yet another picture at the photogenic arse of the spine. The photo on the right is Paul Wallace taking field permeability measurements using a Tiny Perm instrument. He stood like this for 2 minutes each point while Yan read of the numbers, the perks of being a professor. Only joking we made Yan do some measurements too, the perks of being too short to reach! I took some detailed notes while Jackie went round the area taking photographs. Each day we had only approximately 3 hours on top of the dome so team work was critical to getting the work we wanted to do, done.

Again we were very lucky, and with chaperones, we were allowed to enter the exclusion zone directly East of the volcano, here they have amazing structures which channel lahars into the sea. Without these structures the surrounding area would be constantly under threat and would be almost impossible to live in (they are very impressive and can be seen in Google Earth!). We carried out some fieldwork and sample collection in the area before being driven a several meters down the road to the spot where Maurice and Katia Krafft lost their lives along with Harry Glicken and 40 others on June 3rd 1991. The top left photograph shows the direction towards the volcano they would have been looking, at present it looks a very dangerous spot- one which I would definitely not be standing if the volcano were again to erupt today- but at the time this spot was actually a 170 m high ridge. It is very unlikely for material from a pyroclastic flow to reach that high, but that day the hot ash reached the ridge and asphyxiated the victims and burned their bodies. The bodies of the Kraffts and Glicken were recovered, however a couple of Japanese journalists standing only a few meters below were never found. The pyroclastic material (in the photo you can see some of the large boulders in the background) has filled the valley with 0.17 billion cubic metres of material burying houses and livelihoods. The plaque (top right) and memorial (bottom left) are tribute to the total 44 people who lost their lives to the eruption, 43 on June 3rd and one on the 5th June in an adjacent valley. These were firemen, policemen, journalists and scientists. The road on the bottom right is the old road which used to lead to the volcano where famous video footage of a Japanese journalist running from a pyroclastic flow was filmed.

Before we could have a good look around the memorial site we were evacuated. A small earthquake had just occurred while we moved our cars from the top left location to the memorial (so unfortunately we never felt it!) and the authorities were worried of a collapse. We had to wait on the translation from our guides from the observatory translating before we knew what was going on though! Quite an exciting end to a very insightful educational and awe inspiring trip.

If you want to read more about the research the University of Liverpool volcanology group have carried out on Unzen volcano, see Adrian Hornby's experimental work here, and my volcano-seismology work here.