The ‘high-wall’ of a mine has been the undoing of many a geologist (if an opencast mine is targeting something flat and dipping, like a coal-seam, the high-wall is the side of the pit above the deepest bed you are uncovering). Sometimes the undoing is accidental – the geo slips or the high-wall edge breaks away. Sometimes it’s thought to have been deliberate – life was getting a bit tough for that geo. And sometimes it’s thought to have been deliberate, but not on the part of the geo (the other guy came back with an odd smile). So high-walls deserve respect.
Kalimantan, Indonesia. Yet another gaping hole in the ground. Usual brief, go there and see what the story is. Someone, somewhere will be offering some great deal. But is there anything left? The mine is up on a ridge, deserted, but maybe only for a day or two. Regular protocol, circum-navigate the edge, keeping a healthy distance back from said high-wall. Get the broad picture. Look for interesting rocks. In this case, I found a beautiful example of ancient (maybe 40 million year old tidal-bedding).
Then, try and get into the pit. Go down to the bottom and see exactly what the target was. In this case, I stood at the end of the pit and eyed the ‘low-wall’. It’s opposite side the high-wall, and in this case, it was a clean bed of mudstone, from which the coal had been removed. It dipped down smoothly and directly to the bottom of the pit. The view is in the featured image. The low-wall is to the right, and the high wall to the left (with a figure to give scale). It’s not as steep as it looks. Honest.
I walked closer and studied the low-wall for quite while longer. Hmm, steepish, sort of border-line comfort-zone. But I figured I could make my way down it, and even if I did start to slide, I could more or less ski down safely. Then I made my way down, and it didn’t seem too bad after-all. Part way down I stopped and did a little work. This is the view from there:
As I said, not too steep at all! I made it down to the bottom, made some more measurements, then happy I’d figured it out, I headed along the pit. I eventually found the ‘haul road’ and slogged back up to the top, and found our vehicle with the others waiting. I took off my sweat-drenched vest and back-pack and stowed them (including my camera, blast it). Then I heard – a roar. I rushed through the scrub to get a view over the low-wall, to see – the whole face that I had just slithered down, had failed. Several thousand tons of boulders were cascading down to the bottom.
Mmm. Twenty minutes or so. And it wouldn’t have been by high-wall.