The Caldera Run

Walking On The Edge Of The Sierra Negra Caldera

We all knew this was going to be the toughest day. It would be the longest, the most dangerous and the most physically exhausting. The station was located in the very centre of the active caldera of Sierra Negra. This is no trivial crater - its about 10 km in diameter and inside its centre is filled with variously aged and variously dangerous lava flows. At 6.30am, we had already left the rangers station at the national park and began our walk. The first hour and a half was the usual trail we had always taken. It was then a further 30 minutes along the rim of the caldera. When you first see this huge crater - you are kind of taken aback. It is absolutely massive. We found the part of the crater rim where it was safest to take the steep walk down into the caldera. It's at this point where things get tricky. Inside this caldera is basically a sea of lava. Some of the lava is from relatively old eruptions, some - from the most recent extrusion in 2005. There are two types of lava - the first is called pahoehoe. Taken from the Hawaiian name - ropy. This lava bulges out as it flows, forming tongues and toes of material. When it cools, it often has a smooth surface and is not too difficult to walk on. Pahoehoe was our friend. The other type of lava is called aa - taken from the Hawaiian name - hurt. Here, the lava brakes its surface as it moves, crumbling into razor sharp rocks and boulders that fill the floor - like a pile of loose rubble. Aa lava was not our friend. We tried to follow the flows of pahoehoe.

Inside the caldera, were huge mounds of lava - scaling up like mountains in a sea of black and gray. These mounds made it very difficult to see any sort of path, so we just followed our GPS towards the station. At one point, you come to an aa lava flow that is impossible to get around. I was told it takes most people an hour to get across it - and there is no other way. We each had a bicycle helmet on and strong gloves, because if you touch this lava with your hands, they will be sliced to pieces. Last time a volcanologist was in here he tripped in the aa lava and sliced open his head. He was then flown by emergency plane back to mainland Ecuador. Apart from the head injuries, the real risk was twisting or spraining an ankle. This was an easy thing to do with such rubbly material. And if you did do some damage preventing you from getting out - you were in trouble. We were now right in the heart of the caldera and there is no way that people would be able to carry you out from there. The only way out would be by helicopter, so we had our satellite phone on and ready at all times - unfortunately it was cloudy within the crater that day - so the chopper probably wouldn't of been able to land anyway!!!. It was unlikely, but if the volcano decided it was time to go off too - we would also all be in real trouble, as theres no way you could get out in time - we tried not to think about that.

From previous geology trips where I had walked over rubbly material - I had learnt that the faster you went (up to a point) the easier it was to get across. I applied this technique to the aa lava. Essentially you had to dance across it - and actually I didn't find it too bad. The others (Nate and Marco especially) took every step painstakingly slowly and really struggled. After a while I had learnt how to predict where to put my foot before I did and then by that point I was already calculating the next position. The other danger in this ocean of igneous material - are the lava tubes. Sometimes you will put your foot on a piece of what you think is solid lava, only for it to plunge a meter or more below ground. Sometimes, as lava flows, it cuts into the ground its travelling over. The top (exposed to air) cools and forms a crust. Later the lava in the middle drains away - leaving lava tubes or caves. Often the top crust layer is thin and you can easily put your foot (and whole body) right through it. This happened a few times. At other parts of the flow, you would have to leap over giant crevasses. Despite all this - I made it over in 40 minutes. My technique was the key to my speed - I named it - 'the caldera run'. The others soon followed.

When we reached the other side there were some unhappy faces. Marco questioned why four people had to do this whole days trek over wobbly lava, when the station only requires two people to service it. Nate also later claimed that walking for an hour over the aa lava was by far the most dangerous thing he had ever done in his life. I remember thinking to myself that if you want to be a volcanologist, you have to be prepared to walk through some rocky terrain. That's just how it is!!! I never said anything. It took another hour of walking over more lava to reach the station and we had finished servicing it by midday. It was then another 3 hours back to the crater rim - up the steep flank and then a further 2 hours back to the rangers station. On the way back we didn't use our GPS. There was a big tree with bright green leaves shimmering on the crater rim and we all kept that in sight and followed its line. We also spotted an easier way over the aa lava - we found some interspersed pahoehoe, which helped.

By the time we got back to the rangers station, it was 6pm and everyone was a mess. A few angry faces had flared up during our journey - I didn't get involved in any of the discussions. In all, it had been tough, dangerous and exhausting. I remember looking down at my boots and trousers and seeing them completely cut up, destroyed by the razor sharp aa lava. However, it was also a pretty interesting experience. The geology of the lava out there was a volcanologists dream. Amazing stuff. I wouldn't want to do it again any time soon - but I was glad it had been done, and successfully - with no injuries apart from the odd blister. For Nate and Marco however, it appeared to be the final straw. From that point on - there image of the Galapagos had been marred, and by the end neither of them wanted to come back to these islands..........ever!!! There are not too many people who come to the Galapagos who say that when they leave - although I guess not many of them went through what we did. Actually though, it wasn't the final straw, at least not for Nate anyway - that was still to come......................................