If you’ve ever tried to take photos in caves then you will know that a typical camera doesn’t always produce the best results, often the flash bounces off any moisture just in front of the camera and you get a photo of that instead. Plus its muddy and dirty and sweaty so I’m hardly inclined to take my nice camera in. So I won’t be posting any subterranean photos. Yet. Luckily, one of our expert cavers is a decent amateur photographer, with separate flash guns (necessary for caves) and the combination of patience, diligence and obsessive attention to detail required for good photography. So there will be later, at some point, some very, very good in cave photos. With any luck!
Note: we also have a happy snap kind of camera which does produce some decent results, I will try to post some of these at some point.
What’s interesting about our caves is that they’re not underneath the floodplain. We’re in a tower karst area. Imagine the big towers of karst in China and Vietnam that are world famous surrounded by flat paddy-fields and twisting winding rivers. It’s a bit like that, but, because we’re in the tropics, there aren’t these vast outcrops of rocks of the steep sides of the towers, instead there is vegetation. Trees and bushes growing on near (and in many cases fully) vertical cliff faces. The caves themselves lie inside the tower karst up to hundreds of metres above the valley floor. The water has only eroded as far as field level, where huge rivers run underground emerging at the base of the karst before being channelled into canals and rivers feeding thousands of rice-paddies. Thus it is the levels above the river way up in the karts towers in the previously eroded rivers that the stalagmites lie. Drips of water percolating through the limestone leave a thin layer of calcium carbonate inside the cave where they hit the ground. Over time, at a rate of 1cm per hundred years (give or take) these layers of calcium carbonate build up from the floor and down from the ceiling, forming stalagmites and stalactites. Which is what we’re here to collect.
So to get to the caves there’s usually a bit of a hike up the side of the karst, through grikes (dead-straight mini canyons formed in areas of weakness) tens of metres deep to get to the cave entrances. The caves themselves are bigger than I thought they would be, which is a relief. There’s far less crawling and small gaps to get into them, and the chambers are much bigger than I thought they would be.
Small gaps and constrictions are very useful in a cave when you want to collect speleothems. Caves with airflow through them, either from multiple entrances or from wide passages, don’t produce very good records. Or rather they include an extra couple of variables which require interpretation. Caves with a good tight constriction tend to be more humid beyond the constriction which reduces evaporation which can influence the chemistry and also have more consistent air temperatures. So all our good stals come from beyond a tight constriction which requires crawling through. This is good fun, especially when they’re combined with pitches (areas of the cave which are steep enough to require a rope or rope-ladder to help you get up and down. There have been a few of these so far but they don’t pose to much of a problem. Although, as you can imagine, they form a bit of a bottleneck during the walk-in to a cave (often several hundred metres) and so slow us down quite considerably. They are also a pain to get the stalagmites out through!
The rest of the cave tends to involve lots of scrambling, which is good fun as I like scrambling! Whilst there are some big chambers where its possible to walk around quite freely. As a result the inside of the caves are also less claustrophobic than I thought they would be. It’s actually quite natural. Hot though (typically in the high twenties) with near 100% humidity which makes doing anything very hot and sweaty. So when you have to do some physical labour, which is frequently, you can get very tired and drenched very quickly. Plus some of the caves can be very muddy inside.
More will follow, detailing how we collect stalagmites.
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