The drive towards Puyehue-Cordón Caulle began on Tuesday morning, when we set off from Villarrica. As we passed through Los Lagos – the lake region – the plume from the eruption became visible in the distance.
Late on Tuesday afternoon, we turned up in the town of Rininahue and – eventually – found the local Carabineros (police). The police officer on duty took our names and showed us some of his amazing photos from the eruption. Apparently the main park entrance was closed and the best route in was from the north; the carabineros had travelled there on horseback. He gave us instructions on how to find the house of a guide, Hector Para, whose name had been given to us by OVDAS.
With a vague understanding that we were to take lots of right turns and drive twelve kilometres, we set off and – not suprisingly – got completely lost. A shopkeeper and a few passers-by tried to help us, and the outcome was that, a couple of hours later, we were on a steep 4WD track with two very small cars and no idea whether the mysterious Hector was to be found in that direction. We sensibly decided it was time to call it a night, and camped at a flatter spot down the road.
Upon phoning Hector’s number the next morning, and explaining to whoever had answered the phone that we couldn’t make it to his place in our cars, we found ourselves agreeing to meet him next to a fish farm in an hour’s time. In due course, a priest named Gabriel arrived in a big red pickup, and drove us up to the house. We weren’t entirely sure what was happening – Hector wasn’t there, although a few other people were; it was almost noon and probably too late to start hiking into Puyehue National Park; apparently the forecast was for rain the following day and there was so much ash around that we were concerned about lahars. Some discussion followed about the weather and the possibility of starting off early the next morning.
The next thing we knew, we were on another four wheel drive track in Gabriel’s pickup. There was a brief stop so that he could cut us some walking poles.
Then we were walking through a forest that got progressively quieter and greyer as the ash thickened, and out onto and over a series of eerie ash-covered hills. The only animal I saw or heard on the way in was a small lizard, before we entered the national park.
We could hear the booming of the volcano in the distance, getting louder as we approached. In some places, the ash layers were so thick that it felt like walking over sand dunes.
A couple of quick photos of the eruption:
Some of you may have heard about the sad events on Erta ‘Ale early on Tuesday morning, when a party of tourists was attacked. We were due to get up there that night but have cancelled the Erta ‘Ale and Dallol section of the trip and are now in Mekele to the north.
The MRAV conference field trip participants, as well as a group who had attended the conference but were on Erta ‘Ale the previous day, are safe and have left the Afar region. Keep checking our twitter and facebook pages for more frequent updates – and we should be blogging again next week. Our thoughts are with those affected by the incident.
All the best,
A quick update before we head north today. We’ve spent the last three days in Addis Ababa, attending the Magmatic Rifting and Active Volcanism conference. It is a milestone for the Afar Rift consortium, of which the Volcanofiles’ fellow PhD student and officemate, Talfan Barnie, is a member. We’ll be posting more on his work later. For the Volcanofiles, it has been exciting to hear so much about a region in which none of us have worked previously.
In between conference events and travelling around the city, we have been getting together our equipment for the fieldwork on Erta ‘Ale. We’ll go into more detail on the instruments in later posts, but they include a thermal and a video camera, both of which will be pointed at the lava lake; a filter pack for capturing gas and particle information; and a UV spectrometer which is primarily for sulphur dioxide measurements. The field trip schedule gives us two nights and a day at the top of the volcano, so we are more likely to run out of batteries than to run out of time!
We are unlikely to have any internet access for the next nine days, but will be putting up photos and blog posts when we get back.
The sampling that is being carried out this year at Erebus also includes work on lava flows around the volcano. Dave Parmelee is a Masters student at New Mexico Tech., and over the past month he has been travelling all around the Erebus caldera by snowmobile and foot to collect samples from lava flows.
Dave completed his undergraduate study at the University of Connecticut in 2006. He worked for a large environmental consulting company, doing fieldwork in and around Connecticut. Dave and his girlfriend, Danielle, have done a lot of climbing and hiking around the USA, as well as spending some time in Guatemala. In 2010 they went to Peru, where they worked as volunteer scientists at a national park.
Earlier this week, Dave let me accompany him on one of his sampling trips. It was one of the highlights of this field season for me, to get out to one of the more remote areas of the volcano and see what he does. We walked around the Side Crater and down to the southern flanks of Erebus, where Dave collected some lava samples for Helium dating.
Previous studies of Erebus lavas by Chris Harpel have involved Argon dating (see the reference below and the previous post for more information), which gives a possible age range for the flows; Dave is collecting samples for Helium (3He) and Chlorine (36Cl) dating on the same flows. Argon dating at Erebus has high uncertainties, resulting in overlap of the possible ages of different lava flows, so it’s hard to tell which order the flows were emplaced in. In addition to this, excess argon found in Erebus rocks can cause ages to appear higher than they actually are. Excess argon can be cleaned out in the lab, but the results from Argon dating at Erebus are considered maximum possible ages.
The isotopes used in 3He and 36Cl dating are formed when an outcrop is exposed to cosmic rays – so by measuring these isotopes, it is possible to calculate the length of time for which the lava flows have been exposed to the surface. Snow cover around Erebus this year is greater than usual, but this is helpful for Dave’s sampling, as those locations currently exposed are likely to be the same ones that are usually exposed.
There are many challenges in sampling from these lava flows. Snow and ice cover change from year to year. It takes two metres of snow cover to completely shield a rock from cosmic rays, so Dave has to make a judgement on whether a flow is likely to have been exposed constantly. Not all of the flows marked in the published map are well exposed. Dave uses a combination of this map and aerial photographs to identify sample locations.
Near the summit cone, there are large volcanic bombs in addition to the lava flows, so Dave has to distinguish between the two before he can select a place to sample. The location must be relatively flat, to ensure that there is little shielding from cosmic rays and that the production of cosmogenic isotopes will have been at the highest rate possible. He has to avoid locations with steep slopes or topography that may have blocked the outcrop from exposure to cosmic rays – the more open the area is, the better. Samples have to come from the top few centimetres, also to ensure exposure.
Another requirement for 3He dating is the abundance of suitable crystals: He isotopes for dating are, at Erebus, mainly found in a mineral called pyroxene. This tends to occur as small crystals, often incorporated into larger crystals of Erebus anorthoclase. Helium 3 occurs naturally, before exposure to cosmic rays, so the helium inherited from eruption needs to be isolated from that which is produced cosmogenically. By contrast, 36Cl is only produced by cosmic rays.
Once he has found a suitably flat area on the flow (with visible pyroxenes if the samples are to be used for 3He dating) Dave can take notes and photos of the sample location. Things he has to consider include whether the rocks are still in their original location; usual extent of snow cover; the shielding from the horizon, which he measures by taking the inclination of the topography above the flat horizon at different points; and the extent to which the rocks have been eroded.
At this stage, Dave gets to work with a hammer and chisel. Although the rock can be difficult to break up, it also requires some precision to avoid losing any pyroxenes for 3He dating. A minimum of 300 milligrams of pyroxene are required, which may mean carrying back a couple of kilograms of rock. Chlorine sampling, on the other hand, requires a bulk sample of rock, so can be slightly quicker. It can be several hours work to drive and then walk out to a sample location, find a good site, and get enough sample.
Over the next few months, Dave will be isolating the isotopes that are of interest – the 36Cl at New Mexico Tech., and the 3He at Woods Hole Oceanographic Institute in Massachusetts. The amounts of Cl and He isotopes can then be measured. The production rate for the cosmogenic isotopes is calculated, using published equations, from measurements of the isotopes in the lab combined with the field notes, but the result is an ideal production rate – in reality there may have been shielding from topography and snow which is no longer present. As a consequence the age calculated from the ideal production rate may well be younger than the actual age. Combined with the argon dates, this gives a better constraint on the ages of the flows and we can start to understand how periodic the eruptive behaviour of the volcano has been.
Despite all his experience in the outdoors, spending a month on a volcano has been a new and exciting experience for Dave. He has learned to drive a snowmobile on technical terrain and travelled out to parts of the caldera that have not been visited in a long time.
Thanks to Dave for the information and a great afternoon out in the field!
For the paper on Argon dating of Erebus lava flows: Harpel, C.J., Kyle, P.R., Esser, R.P., McIntosh, W.C., Caldwell, D.A., 2004. 40Ar/ 39Ar dating of the eruptive history of Mount Erebus, Antarctica: summit flows, tephra, and caldera collapse. Bulletin of Volcanology, 66(8): 687-702.
Tephra sampling has the widest spatial range of any Erebus project this year. Nels Iverson is a postgraduate student at New Mexico Tech. studying towards his Masters in Geology, and his fieldwork in Antarctica has taken him from the top of Erebus volcano to the sea ice, and out to the Polar Plateau over 200 kilometres away.
Nels did his undergraduate degree at the University of Hawai’i at Hilo, and has also worked in Washington and Oregon, mapping basaltic rock. Although he has spent a lot of time in the field, this is his first project in tephra and geochemistry. He is in his second Erebus field season.
Volcanofiles: What is tephra, and why are you sampling it?
Nels: Tephra is anything that erupts from a volcano from the size of ash to blocks the size of cars. We are sampling it to look at Erebus’ past geochemistry and to date it, to better understand the volcano’s past eruptive activity.
Volcanofiles: How do you collect tephra samples? Do you find any blocks the size of cars?
Nels: Fly around in helicopters ‘til we see black stripes on glaciers! We use satellite imagery first to scope out spots, do reconnaissance by helicopter, then sample via chainsaw. The tephra grainsizes here range from less than 30 microns (a micron is a thousandth of a millimetre), to one millimetre.
Volcanofiles: How exactly does the chainsawing and collection work?
Nels: Each one of the black layers is hopefully an ash layer, so we cut a block of ice out of the glacier, then trim it up to just get the black layer. We throw them in coolers, take them back and melt the ice blocks to extract the tephra.
Volcanofiles: Is a black layer always ash?
Nels: We also get windblown sediment. Some places it’s easy to tell because there are melt pits of gravel on the glacier, and it’s not glassy like tephra would be. We have also found places where one ash layer has contaminated another layer, with three chemical signatures in one place.
Volcanofiles: Are these layers only found in glaciers?
Nels: No, there are also layers in the Dry Valleys on the Antarctic continent but it’s much easier to spot tephra in glaciers. Some of these areas will have forty ash layers in one section of blue (glacial) ice, compared to maybe two layers in an equivalent area of the Dry Valleys. The tephra layers in the glaciers are found where ablation (removal of ice from the surface) has brought the ash up from depth.
Volcanofiles: Is all the tephra you find from Erebus, and how can you tell?
Nels: All but two ashes we have found are from Erebus. We use an electron microprobe to do chemical analysis of major elements, from which we can discern whether the ash is from Erebus or not. We have two ashes that are not of the normal Erebus lineage. Possible sources are the Pleiades (northwest of us), or West Antarctica (to the east of us).
Volcanofiles: How do you do the dating?
Nels: We use the 40Ar – 39Ar method. It is a proxy for the K-Ar system. In order to use it, we have to irradiate the samples in a nuclear reactor.
Volcanofiles: The quick version: K-Ar dating method relies on the slow natural decay of a radioactive form of potassium, Potassium-40 (40K), into Argon-40 (40Ar) over time. It takes about 1.3 billion years for half of the total amount of 40K to decay (this is the ‘half-life’ of 40K). So, assuming that no new argon can get into the mineral sample, the amount of 40Ar can indicate how much time has passed since the potassium-bearing mineral was formed.
40Ar – 39Ar dating involves irradiating the samples in order to convert the 39K (which is stable and does not decay under normal conditions) to 39Ar, which does not occur naturally. This argon isotope indicates the amount of 39K originally in the sample. Since the usual ratios of different potassium isotopes are known, the amount of 39Ar can also be used to indicate the amount of 40K originally present – so just by measuring the ratios of different argon isotopes, a relative age can be found for the sample.
Volcanofiles: What other sorts of geochemical analysis do you do?
Nels: We do Laser Ablation ICP-MS to look at trace elements, which is another way to understand the evolution of the volcano. Erebus is very stable geochemically – at least over the past 30 000 years it has been fairly chemically stable.
Volcanofiles: What kind of evolution are you expecting to find?
Nels: There is a time where the composition changed from a tephriphonolite to a phonolite. The main part of the project is to date the ash layers – we already know about the different layers but we can constrain them in time.
Volcanofiles: Why is it important to study tephrochronology and tephrostratigraphy?
Nels: It’s important because these ash layers can be traced over large areas and can have large effects on snowmelt. Tephra layers can be used to correlate ice cores and their ages. Erebus doesn’t have any known tephra layers in ice cores, but other volcanoes in Antarctica can be traced across several difference ice cores.
Volcanofiles: So how far away are you finding these Erebus layers?
Nels: We have one layer 200 kilometres away in Manhaul Bay in the Allan Hills, and one in Mount Dewitt which is about 39 000 years old.
Volcanofiles: This is your second field season here – what were your fieldwork goals for last year and this year?
Nels: Last year we sampled many different locations to get a good spatial coverage. This year is for collecting more samples to get more dates. We did sample a few new spots that were either previously covered by snow and are now uncovered and locations we didn’t get to last year. There were some this year which we wanted to sample but were covered by snow.
Volcanofiles: How have you found the transition to working in Antarctica and geochemistry, after your work in Hawi’i with lava flows?
Nels: I love it. It’s such a treat to come down here and work. It’s been the experience of a lifetime. It’s a whole different ballgame flying around looking for black spots in the ice and chainsawing them out. You’re only working with a few grams of ash – you have to be a lot more careful. It’s meticulous work. It’s very interesting – it’s a different side of a volcano that I was never exposed to before this.
For a published study on Erebus tephrostratigraphy: Harpel, C.J., Kyle, P.R., Dunbar, N.W., 2008. Englacial tephrostratigraphy of Erebus volcano, Antarctica. Journal of Volcanology and Geothermal Research, 177(3): 549-568.
Among the unique features of Erebus are the systems of ice caves and towers formed by fumaroles on the volcano. Aaron Curtis is a PhD student at New Mexico Tech., currently in his third Erebus field season studying the ice caves. The research he is undertaking here is the first of this kind to be published since 1976. He tells us about the work he has been doing in the caves over the past few weeks.
Volcanofiles: What is an Erebus ice cave?
Aaron: I’m studying fumarolic ice caves and towers – these caves are more like glacier caves than like limestone caves containing ice. There are similar things at a few other volcanoes – Mt Rainier, Mt Baker in the Cascades of the northwest US, Mt Melbourne in Antarctica and several in Iceland – whenever you get a volcano under a pretty large amount of snow. There’s nothing like Erebus in terms of the number and diversity though.
Volcanofiles: So how are these fumarolic ice caves and towers formed?
Aaron: Well, nobody knows exactly, but that’s what I’m studying. The volcano releases gases and heat from the entire summit caldera area, and the permafrost and perennial snowpack is reshaped by that heat. One of the common results is that you get voids developing at the bottom of the snowpack and some of those are spectacular networks of passages. Some of the cave entrances have towers on them, and are linked up to towers.
Volcanofiles: Are they are all formed in the same way?
Aaron: It seems like there could be two major mechanisms of heat transfer. The first is conduction through the floor. Werner Giggenbach, in the 1980s, wrote about areas of warm rock causing caves to appear above. But what I’ve been finding, which wasn’t reflected in earlier research, is that there are discrete fumaroles that have a huge impact on the cave geometry. I think what the networks we can see are most directly a result of airflow from discrete vents, because there are fractures and shallow structure in the rock that controls where the heat goes and where the cave forms.
Nial: The scalloping on the walls shows that there is hot gas flowing through the cave, rather than just hot ground. (Although Nial is currently doing his own PhD work here, his first Erebus season was as Aaron’s field assistant, so he has spent a lot of time in the caves!)
Aaron: Exactly, and the microclimates of the caves are completely different from the surface. Our average surface temperature is -32.6oC over the year, whereas the cave temperatures are between 0-6oC all year. There is really strong airflow in some caves which indicates that hot air is coming through the bottom and spewing out the top.
Volcanofiles: What about the humidity?
Aaron: It’s pretty close to 100% relative humidity. We see liquid water in some of the caves. The presence of water in environments such as these is a huge deal for biologists – it’s kind of like an oasis in a polar desert. We at the Mount Erebus Volcano Observatory are interested in how closely the steam coming out of the vents is linked to the magmatic system – whether it’s degassing directly out of magma, whether it’s recycled melted snow, or whether it reflects a hydrothermal system.
Volcanofiles: So how do you carry out these studies?
Aaron: The main focus in my research for the last couple of years has been fibre optic distributed temperature sensing (DTS) investigation of the cave microclimates. That allows us to see all of the discrete fumarolic vents and compare them to the environment in the rest of the cave.
Volcanofiles: What is DTS and how does it work?
Aaron: The cables are strung out in the cave, and we fire a laser down the cable. This gives us reflections from down the length of the cable. The temperature at every point on the cable affects the spectra that we get back. We send out a specific frequency signal and we get light back at several different frequencies. Some of those frequencies are affected by temperature so we can compare them to get a precise temperature. The electronics allow us to measure very finely the time when the response gets back, which relates to the distance along the cable, so we can measure different temperatures for every metre of cable.
Volcanofiles: How much distance are we talking about?
Aaron: Probably up to 1 km for one of the caves I’m looking at. The large ones are on the order of hundreds of metres, but some of them are barely big enough to get your head into – those ones are a bad idea to put your data loggers into because you don’t tend to get them back!
Volcanofiles: So the caves change a lot?
Aaron: I’ve been astonished by the differences in caves just from one field season to the next. The passages seal off and whole new sections will open up – it’s kind of a weird feeling because the caves are vaguely familiar from last year so it can be quite disorienting. We just finished the first repeat LIDAR 3D scan (which Volcanofiles will be posting more on soon!) of Warren Cave – we mapped it in my first year and did the LIDAR the two following years. Drea Killingsworth will be able to tell you more about that.
Volcanofiles: Are there any other instruments you’ve got in the caves?
Aaron: I’m monitoring about 15 different caves using various data loggers for temperature, windspeed, barometric pressure, and CO2 concentration. Other work I’m doing includes taking a bunch of gas samples and biological samples, and thermal imagery. I also have a multigas meter which I can take in with me, that checks for CO, SO2, H2S and CO2 – primarily for safety, but it gives us a bit of science as well.
Volcanofiles: Can you tell us more about the unusual crystal formations in the caves?
Aaron: They’re spectacular and hugely variable. The cold areas in particular have crystals that can be up to a metre long, and clearly reflect the microclimate in that particular area. They can even tell you the wind direction – some of the hoarfrost grows into the wind. It’s almost like having a vector field mapping out the wind direction – the kind of thing it would take a really advanced instrument to be able to do, but nature does it for us.
Volcanofiles: How accessible are the caves?
Aaron: Access varies from being able to walk in to pretty technical rope setups. Every cave is different. Some caves we have not been able to get into at all.
I feel fortunate because I get to stay down in the nice warm protected environment while other people are up at the rim – but it’s humid down there, and when you come back to the surface, your clothes turn into armour when everything freezes. Snowmobiles don’t have seatbelts so it can be convenient when your butt freezes to the seat…
Volcanofiles: Thanks, Aaron! Good luck with your work down Warren Cave today.
For more about the DTS work Aaron is doing here, here’s the reference for his paper recently published in Geophysical Research Letters:
Curtis, A & Kyle, P., 2011. Geothermal point sources identified in a fumarolic ice cave on Erebus volcano, Antarctica using fiber optic distributed temperature sensing. Geophysical Research Letters 38:L16802.
In order to spend time at the Erebus camp, we first need to have a couple of days of acclimatisation at a lower altitude. The usual site for this is at the Fang glacier on Erebus (about 2900 m), where we are based in tents for a couple of days as our bodies adjust to the altitude.
Those of us in the second group had fairly good weather. We spent most of our time there in Scott tents that had already been set up by the field support people at McMurdo.
When acclimatising, it’s better to stick to light exercise, so we went for a short walk near camp and visited the glacial moraine, consisting of eroded volcanic rocks that were redeposited by a glacier.
To the east, we could see Mount Terror, another of Ross Island’s volcanoes.
Terror and Erebus were named after two ships in Sir James Ross’ expedition in the 1840s.
Apologies for the lack of recent updates! This post will cover what we got up to during our last week at McMurdo.
Hut Point and Discovery Hut
Although Erebus is the only active volcano on Ross Island, three other volcanic centres are also located here, including Hut Point peninsula. For now, here‘s a map of Ross Island that you can zoom into to find the peninsula, McMurdo Station, and a few other key locations. One of the walks near McMurdo is along the Hut Point Ridge. I chose the clockwise direction, which passes the historic hut built at the start of Scott’s 1901-04 Discovery expedition:
There were a few seals sunning themselves on the sea ice near Vince’s Cross, which was originally erected in 1902 as a memorial to a drowned crew member on the Discovery.
The walk follows the ridge of the peninsula for a short way, with views of McMurdo and beyond, including Observation Hill:
The walk goes as far as a place called Arrival Heights, where I could finally get a good view of Erebus – although the summit was still obscured – before following the road back to McMurdo.
Barne Glacier/Cape Royds trip (aka penguins and historic huts)
The highlight of the weekend was a sampling trip on Sunday 28 November. One of the G-081 team members planned to sample some volcanic ash from the Barne Glacier, which would mean a trip by snowmobile across the sea ice.
It was a nice morning, which meant plenty of chances to enjoy the views:
while we stopped to check that any cracks in the sea ice would be safe to cross:
Sea ice is an upper layer of frozen seawater that still undergoes tidal changes. Some cracks represent weak areas, so we needed to drill through them to make sure that the ice was thick enough, and remained thick enough, over a distance that was safe for snowmobiles.
We found a safe route and made it out to the Barne Glacier, which comes off the western side of Mt Erebus.
We continued on to Cape Royds, where there is a colony of Adelie penguins. These are the most common type of penguin in this part of the world.
We can observe the penguins from a distance – the scientists studying them get a bit closer.
Although we saw some Emperor penguins in the distance, they stayed near the open sea.
The next stop was Shackleton’s Hut, a short walk away. This hut was erected in 1908 during Shackleton’s Nimrod expedition, and was the base for the first ascent of Erebus just a few weeks later. We also stopped at Scott’s Hut at Cape Evans on the way back to McMurdo. This hut was built in 1911, and it was from here that Scott’s Polar party set out – just over 100 years ago.
We looked around the hut for a while.
It was an opportunity to reflect on the history of Antarctic exploration and science – to appreciate both the privilege of being here and the comparative luxury in which we work.
Then it was time to head home – the wind had picked up and visibility had dropped, so we were grateful to return to the warmth and comfort of the station!
More catch-up and an update schedule will follow. We’ve had a busy few days, with acclimatisation to altitude at Fang camp; moving up to the hut where we’ll be based for the next month; setting up tents and snow walls; testing equipment; and, for a few intrepid team members, trips to the caves and crater rim despite the bad weather.
The reduced visibility and blowing snow continue, but today we managed to do most of our food pull – collecting all the food we are taking to Erebus, some of which we will take to Fang camp (where we spend a couple of days getting used to the altitude), and what will go up to Lower Erebus Hut (where we spend most of the field season).
One of the training sessions we had today was run by a couple of the G-081 team members, Aaron and Meghan. Aaron’s work is in the ice caves on Erebus, so they showed us some techniques for rappelling into and ascending out of the caves.
After dinner, I decided to head over to Scott Base for American Night – because the NZ base is so much smaller (about 80 people at the moment, compared with about 1100 at McMurdo), there’s just one night a week where anyone from McMurdo is free to visit without an invitation. Since the conditions weren’t suited to the walk – which takes about 30 minutes – I took the shuttle. While waiting outside for the return trip, we got an amazing view out across the sea ice, including the transition from the shelf ice (which is connected to and fed by ice overlying the land) to the sea ice (which is a thinner layer of frozen seawater).
Here’s hoping for more good views tonight as I head back to my dorm.