Few things in life are more disconcerting than realising you’re in the middle of a minefield. Of course, for thousands of unlucky people around the world that’s a daily reality, but that’s another story. Here we’re comparatively lucky: the ground doesn’t go bang when you step in the wrong place, but it might just give way. Crevasses: the bugbear of icy travellers, and for the last week or so we’ve been caught in a particularly unpleasant spot with holes all around us.

Before my mum has a coronary, I should make one thing clear right now: we’re not talking about enormous, bottomless Chasms of Doom here. But a hole a couple of metres wide and a few deep, such as the ones we’ve encountered, would be enough to put a Cat out of action, give its driver a serious case of the heebyjeebies, and ensure that we have to spend the winter right where we are. And nobody, least of all my mum, wants that.

Step one in trying not to fall into crevasses is to predict where they might be and what direction they run in. Crevasses usually form when ice is put under tension – for example on convex slopes, near the brows of hills, or where moving ice such as a glacier has to change direction. At the moment we’re on a large patch of hilly blue ice – not a moving glacier, but it undulates gently all around us: convexities and concavities abound. Our theory is that it’s being pushed up from underneath, perhaps by hilltops far beneath our feet which stretch and crack the ice surface in all directions like a good, crusty French loaf. The bad visibility we’ve had here makes it hard to get a good idea of the lie of the land, and there are simply no detailed maps of the area. The only picture we have of what’s ahead is the very same, low resolution Google Earth photo that you can see on your computer. That gives a rough idea of the terrain on a macro scale, but nothing like the detail we need. Part of our science programme, by the way, is to accurately plot the surface of the ice sheet as we travel, which will help with future mapping.

So much for prediction; what about actually finding the pesky little blighters? In theory our ground penetrating radar (GPR) can spot crevasses, and it’s served us well in the two crevasse fields we’ve come through so far. Usually I tow the radar antenna ahead on foot, while Brian monitors the display screen (attached to the antenna by a long cable) and radios me when it shows a crevasse under the antenna. We can then mark it with bamboo poles and decide how to tackle it. GPR is good for spotting isolated crevasses in otherwise uniform terrain, but when we’ve used it here it picks up every small crack in the shattered ice; there are so many signals we’d never get anywhere if we investigated every one.

Experienced polar travellers will tell you that the best crevasse-finding technology is the mark 1 eyeball. After assessing the terrain to predict likely slots, you can often spot the crevasses themselves by a slump or a change in texture in the snow bridges that cover them. The lack of surface contrast here makes this very difficult, and changes in snow feature may just be wind-tails off sastrugi in this very windy place. Traditionally, when you see a crack you bash it with a ‘bog chisel’ – a long wooden pole with a steel chisel on the end. This gives you an idea of whether the snow bridge is strong enough to walk across. However, what it won’t tell you is whether it’s good enough for a 25-tonne bulldozer. Ironically, getting through here would be a breeze if we were travelling on foot.

So that’s the pickle we find ourselves in. Over the last few days Bri and I have made several recce missions on foot to try and find a suitable way out. Navigation during these sorties is pleasantly old-skool: keep the wind on your left cheek on the way out and count your paces for a kilometre or two; then keep the wind on your right cheek on the way back, and hopefully you’ll spot the caboose. GPS helps confirm where we are and records our track for use later. Meanwhile, Rich and Spencer have been using the Cats to fill in what holes we have found and doing some maintenance, and Ian has continued with the never-ending task of caboose maintenance between bouts of filming.

Nine days after getting onto the blue ice, we think we’ve found a route out. There are certainly crevasses there, but at the moment it’s the best option we have. We’ve looked at all alternatives, taken the time we need, and done as much as we can to minimise the risk. Once the weather improves (hopefully today), Rich and Spencer will saddle up and we’ll press onwards, moving in short hops of 500 metres or so and never letting our cabooses get too far away from our fuel supply in case the worst should happen. Spare a thought for the drivers – having never seen crevasses in their lives before, they now find themselves driving hefty vehicles over something akin to frosty Swiss cheese – though Rich maintains that a lifetime in Armagh has prepared him well for sudden bangs and big holes appearing in the ground.

True enough, as minefields go it’s not the most brutal, but we’ll be very happy puppies once we’re out of here.