This morning it dawned on us that we have less than a week left here in Kenya. Although I will very much miss this place, even more so the lovely people we have met, I am looking forward to coming home. I can’t believe how fast our time here has passed, but they do say ‘time flies when you’re having fun’!
When mapping it is always nice to come across a contact between two different rocks. Inferring boundaries can be quite tricky.
Today we completed the mapping of the caldera. We focused on the western section, but it didn’t take us long as there were only a couple of lava flows to put on the map. We did find a nice chilled margin at the contact between the two flows.
The chilled margin. Very-fine grained, glassy at the contact with grain size increasing upwards away from the contact.
A chilled margin is where you can see a gradation in grain size, from a very fine grain size at the contact getting coarser as you move away from the contact. At the example we observed today there is a narrow band of glassy material about 10mm thick, then a coarsening of the grain size upwards away from the contact.
We also discovered some old lava flow channels - at least I’m pretty sure that’s what they were.
The channels within the pahoehoe lava.
These former channels were very smooth sided and cut through the ‘ropes’ of the pahoehoe lava flow in which they occurred. There was a small network of these channels over an area of about 250m sq. Each channel was about 4-5m wide. I think these channels were formed by rivers of lava flowing over an earlier lava which had cooled, or even just semi cooled. Something like this:
On our way home we stopped at one of the well sites we haven’t yet visited. This well has already been vented for some time to reduce the sulphur levels, as the sulphur causes the funnels (and turbines) to rust. Here is an example of what too much sulphur in the rising steam does to the expensive equipment.
Some rather rusty funnels. This rust is due to the sulphur in the steam which was funneled through.
Although we have now mapped the caldera, there are still a few things we want to go back to and look at in more detail, or that weren’t important to the mapping but now we have the time we can go back to. So we certainly have a lot to do in the 5 days we have left.
Again, as we were doing the same today as we have done the past week or so there isn’t really much more to say about our work today. So I will leave you with a tip… don’t apply suncream to your eyes. It hurts.