Erebus science – ice caves

Erebus science – ice caves

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.

Aaron at work in Cathedral Cave last week. Photo: Nial Peters

Aaron at work in Cathedral Cave last week. Photo: Nial Peters

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.

Ice Tower Ridge on the western side of Erebus.

Ice Tower Ridge on the western side of Erebus - an accessible and concentrated group of ice caves and towers.

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.

Aaron at Sauna cave in 2010

Aaron at Sauna Cave in 2010. Sauna is the warmest of the Erebus caves that Aaron has worked in, at about 40 degrees Celsius. Photo: Nial Peters

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!)

Scalloping at the entrance to Warren Cave. Photo: Nial Peters

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.

Gases coming out of a tower on Ice Tower Ridge. Photo: Nial Peters

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.

Some of the icicles are pretty unusual in shape! Photo: Nial Peters

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.

Aaron, Tehnuka, and the DTS cable in Cathedral. Photo: Nial Peters

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!

Aaron in Cathedral. Photo: Nial Peters

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.

Among the crystals found in the ice caves are hexagonal crystals that can grow up to about 15 cm across. Photo: Nial Peters

An example of needle-like crystals that also occur in some caves – these can be up to a metre in length. Photo: Nial Peters

Directional hoar in Periscope cave. Photo: Aaron Curtis.

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.

Aaron (and his pack) abseiling into Cathedral. Photo: Nial Peters

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…

Aaron about to head back to the camp after an evening working down Cathedral

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.

The light in some of these caves is amazing. Shooting Gallery visit - from left, Clive, Meghan, Aaron, Paige, Nial, Tehnuka. Photo: Nial Peters

16 thoughts on “Erebus science – ice caves

Linda AikenPosted on  2:22 am - Jan 5, 2012

Wow! I’ve wondered what you are doing, Aaron, and why you keep returning. This was very interesting!

From Tampa (which I think is cold at 50),


keith curtisPosted on  9:59 pm - Jan 5, 2012

Fantastic. Excellent explanation and beautiful pictures. Could be right out of Star Trek – “where no man has gone before”. Does seem like if there is running water, heat and light, there should be life, no?

keith curtisPosted on  10:18 pm - Jan 5, 2012

also, is there a reason other than that you use the term abseiling instead of rappelling?

    Kayla IacovinoPosted on  6:00 pm - Jan 6, 2012

    I’ll have to direct that question to our cavers/climbers Nial & Aaron!

    Tehnuka IlankoPosted on  8:27 pm - Jan 7, 2012

    Hi Keith! Thanks for your comments. Re: the term ‘abseiling’ – I don’t think I put much thought into it. I’m pretty sure Aaron generally calls it rappelling, so my instinct was to call it abseiling for the non-cavers amongst our readers, who may have been more likely to recognise it. Before meeting Aaron and Nial the only ropework I’d done was on an indoor climbing wall… 🙂

Terence McCormallyPosted on  5:36 pm - Jan 6, 2012

Anna and I looked at your photos. Looks great! Do you have to worry about this ice collapsing on you while you’re crawling around? Sounds like Erebus is at least modestly active, with the venting that is described. Do you have any magma on the surface there? See you soon, Aaron!

judy GrunerPosted on  5:42 pm - Jan 14, 2012

Wow, pretty impressive! I really enjoyed reading this and looking at the spectacular photos.

Keep it up, Aaron!

Judy Gruner from Reston, VA

Mel StephensonPosted on  6:07 pm - Jan 16, 2012

Hi, I’m writing a fictional book and Mount Erebus features. I am a complete novice in the science of it all and right now I am struggling to understand where the ice caves are-are they under the volcano or around the edges? I noticed a previous comment you said the worry was the ice collapsing under you, so what would be under you. Stupid question I’m sure… Thanks

    Tehnuka IlankoPosted on  6:39 pm - Jan 26, 2012

    Hi Mel,

    Thanks for your question. The ice caves we’re talking about here are within the caldera, so are relatively high up the volcano. They are pretty shallow (not really ‘under’ the volcano) as they are formed in the ice that covers the volanic rock.

    The concern about collapsing ice is when we’re walking around on the surface, or in an area where the floor doesn’t have any volcanic rock directly under it, as it’s possible there are caves below us. In that case, you need to be careful not to fall through into a cave (or get your leg stuck through its roof).

    Hope that makes sense!

AaronPosted on  10:24 am - Jan 24, 2012

So, biologists have found microbial life in the ice caves. Do these polar oases occasionally attract stray migratory birds who have overshot their usual routes and drop by for a rest? Are there any edible flora inside the caves? (Unlikely I guess, unless some light can diffuse in) Or they could take a sip of microbial-rich water or from the melting icicles? Maybe they could drop down into a steam plume of one of the less hot and humid caves and fly out the same way. But they might be at risk of having their wet bird feet getting frozen to the outer surface on their way out – sort of like your bottom gets stuck in your snow mobile. Please tell me what animal life you have noticed in or around these ice caves.

    Tehnuka IlankoPosted on  6:44 pm - Jan 26, 2012

    Hi Aaron,

    Thanks for your message.

    I’ve never seen any animal life at or around the Erebus camp – apart from humans and scientists. This year we did spot some snow petrels flying around the volcano when we were acclimatising at Fang, further down, but that is pretty unusual!

    Best wishes,

Erebus science – thermal imaging | VOLCANOFILESPosted on  2:21 pm - Jan 17, 2013

[…] at the data from it. Nial first went to Erebus as a field assistant for Aaron Curtis, who we interviewed last season, working in the ice caves – so he knows the volcano well. Here’s his email interview […]

McMurdo station, Antarctica: 2015-16 Erebus field season | VOLCANOFILESPosted on  11:53 pm - Nov 20, 2015

[…] Instead of working on gas emissions from Erebus lava lake, we are collecting gas samples in the ice caves. Last time, with G-081, (who will also be heading up in January this season) I was in a group of […]

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