Location
Active volcanoes not only spew lava, but also hot gases, some of them toxic, some of them just warm air with various amounts of steam and CO2. The vents for such gases are called fumaroles. They commonly form as magma brings groundwater to a boil, forming steam that mixes with volcanic gas and air from the cracks and pores in the volcano, and finally rising to the surface.
So what is special about fumaroles forming on an ice-covered volcano in an extremely cold environment like Erebus? Two types of fumaroles can be found depending on if they are located under the ice that cover the volcano or open cracks in exposed volcanic rock. 
Fumarole ice chimneys and caves are formed when steam vents on rocks builds up at the surface. These are easily amongst the most spectacular features on Mt. Erebus. There are hundreds of steaming ice towers around the summit region, and just as many caves, of all sizes, shapes and forms. Most of them are quite small, but many of them spectacularly large. Some cave systems require days to explore and some ice towers are visible from as far away as McMurdo Station.
So why are we interested in these caves and ice towers? Regular readers of this blog will quickly recognize that they are extreme environments suitable for studying microbes at the rock bottom of the food chain. In fact, these fumaroles offer exciting “windows” into the deep biosphere of Erebus volcano. 
The ice on top of the volcano is just another geological layer and getting to the bottom of it is, strictly speaking, inside the volcano, below the surface of the solid earth. Because there is little or no sunlight, most of the energy and building blocks for carbon fixation come from the rocks themselves as well as the gases and fluids circulating through them. Unlike other caves, these have no bats, birds or rodents that can introduce organic matter into caves.
We spent almost our entire two weeks on Erebus exploring ice caves and ice towers. We recovered our experiments from our earlier deployments and we explored and sampled many more. This type of work requires some mountaineering experience, strength and endurance. The Field Safety Training Program (FSTP) at McMurdo provided us with a full time mountaineer for this trip, Alasdair Turner, who helped us train for this task and watched out for our safety. He also happened to be a professional photographer who produced some spectacular photos.
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