AfricaArray Field School – The Field pt 2

Part two of the field component of the field school. Again, this is a collection of pre-written posts.

AfricaArray Field School – Day 10

We had a bit of a rest day today, in order to collect samples to determine their physical properties. For some reason, each group needed ten samples of each lithology, of which there are five (according to Sue: granite, quartzite, dolerite, basalt and a granophyre). I saw some of the other groups, who had a couple of other types instead. Notably, what at least one group was calling dolerite, we are calling basalt (because you can see the flow structures, so it is probably not intrusive…).

In order to measure density, we have to get an average weight in air and water of each sample, so each group has about 500 readings to make. Which is going to occupy the evenings, between regular processing.

Other stuff that happened today was some basic stuff related to the vehicles: how to hitch a trailer, how to change a tyre, that sort of thing. I believe that there was some amusement about this, given what people previously knew about cars. Anyway, at least one tyre was changed, and hopefully it will not fall off on the way back.

Otherwise, people were cleaning up some of the stuff that they had stuffed up, regarding processing. In particular, the seismic guys were trying to get rid of some noisy data (there was a tractor in the next field during one of their lines). I was busy playing with QGIS again, and have made a nice enough map of where everyone has been (mostly). So that was at least a useful way to pass some time. I ended up sitting around the fire for a while before bed, which was good fun, and not something that I have had a chance to do yet.

AfricaArray Field School – Day 11

Today we were unleashed on the magnetometer, in order to try something new. We invalidated all the warranties and mounted the sensor of the walkmag on a broomstick, in order to hold it closer to the ground.

The reason we were doing this was to try and get very detailed coverage of an old farmhouse, which is now basically just some stone foundations. It worked reasonably well, but we will need better indications of exactly where on the site everything is. Also, there is an unfortunate propensity for every plant in South Africa to have thorns. So trying to survey straight, even with the aid of a guide rope is somewhat difficult…. Anyway, we got some data, which looks ok, but will need to be more carefully spatially oriented.

Once we had gotten back and dismantled the base station, it was time for the annual staff/instructors vs students soccer match. The field was a bit small, and the sidelines were marked clearly (by thorn bushes, of course), but there was some good skill on display. Mostly by the students, who won 4-2. One of the 4 to the students was an own goal, so the staff are claiming a 3-3 scoreline, and since someone’s shoe went through the goal, that is also being claimed as counting for more. So the official report might be 3-3+shoe in favour of staff, but do not believe it….

The evening was, once again, consumed by data processing. I think that that is one thing that I prefer about geology fieldwork: the evening maps are (usually) easier than fighting with computers. Although I guess that sticking to one method would mean that it is done much more quickly.

AfricaArray Field School – Day 12

Today we took on one of two geophysical methods “seismic and everything else”. Given that the attentive reader will have seen that we have done “everything else”, this leaves us with seismic. I proposed a line across the middle of the field, since I remembered seeing something strange in the EM data associated with a topographic irregularity. It looks like there might be something strange going on, so that was a nice call.

So, we set out the geophones and it was hammer-time. We needed to finish this fairly quickly, because it was the “goodbye to the field” party in the evening. This proved to be lots of fun, with all the students getting awards (I got the “Decartes Award” for my mapping stuff, although I would have thought that “Mercator” or “Waldseemueller” would have been more appropriate, given that Decartes never really did cartography. Ah well….

People ended up getting to sleep pretty late.

AfricaArray Field School – Day 13

In the morning I woke up far earlier than I should have, to help do one more resistivity line, before the bus arrived. That was done, and we were back in JHB and unpacked pretty early on. The rest of the day was ours, so I got caught up on sleep, mostly. In consequence, not really much to talk about today.