By Nick Scroxton.

Stalagmite section under a drill

The next stage in my stalagmites’ journey from cave to scientific paper involves a little necessary destruction. Having spent a few days making my stalagmites look as pretty as possible (see here), its now necessary for me to run a trench down the middle of them This is in order to collect powder samples.

Each layer of a stalagmite records the changing chemistry of the drip-water from which it is precipitated. And the cause of the changing chemistry is change in the environment. In order to find out what these changes are (or more accurately, were), I have to take samples from my stalagmite and analyse them in a variety of fancy machines we have here in the department. These machines will tell me what relative concentrations of what various chemicals and isotopes are making up the stalagmite calcite.

In our research group we have a couple of mills set up for milling powders from corals and stalagmites. Progress is slow and steady and rather tedious. My stalagmites typically grow at a rate of about 4-5mm per 100 years. If I want to sample at 50-year resolution then I need to take one sample every 2mm. On a good day, I can get through 50 samples (10cm) before I drive myself completely mad and run from the room screaming “no more, please don’t make me do any more”.

What makes the whole issue difficult is getting the powders from the stalagmite trench where they have just been milled into the sample vials. This is done using a small, flat metal stick to scoop up the powder. It is tricky and dextrous work that requires a very steady hand and strong concentration. Plus, everything has to be properly labelled, catalogued and the co-ordinates of the mill written down at each successive step. On the upside, it’s a day where I don’t have to do much heavy thinking, I can have the radio turned up and I get to play around with compressed air to clean everything off between samples.