Today was a nice change from the usual, and more like the fieldwork I’m used to. We gave Vincent the day of and walked into the caldera from our accommodation.
It is an easy enough walk down into the SE ‘corner’ of the caldera from Maili Saba. In fact it makes the foreground of the view from our balcony. We were going down here as it is the other place where there is access to the caldera walls. As is always the way however, this is the least interesting region in the caldera in terms of structure; there are no faults here. Added to this the walls here are littered with landslides which hide much of the exposed rock and any fracturing within the walls.
Though seeing as we can at least get to the walls here and have a good look for any structures it was worth a try.
We were also going to see if we could access the other side of one of the lava flows to collect some samples, depending on the terrain to get across to it.
Although the caldera walls in this region don't show much to allow any substantial structural maping , they do make a home for the Rock Hyrax. The rock hyrax are usually very shy and run away before we've even seen them, but this guy stayed put long enough to get a picture.
Lucy, one of the girls who works here at Maili Saba and is also the resident tour guide led us down into the caldera. When we first arrived Lucy was very interested to learn all about the geology here. She will often bring us rocks and ask us what they are and how they formed. So it was really nice for us to be able to work together today. She was telling us how she is very disappointed that most of her clients are only interested in the plants and wildlife, meaning she only occasionally gets to talk about the geology.
It was lovely spending the day working with Lucy. Her enthusiasm for geology is great!
Within the first 10 minutes of walking we encountered the baboons. They were happy playing amongst themselves and weren’t at all interested in us. Helen was still quite nervous, though Lucy assured us that as long as we appear confident walking through the troop they wouldn’t bother us… this approach worked. It only took us 20 minutes to get down into the floor of the caldera. The lava forming the walls at the base was very layered, looking almost sedimentary from afar. I have seen layers within a lava flow, but never as thin as these- they were only a few cm’s thick at most.
The most sedimentary looking lava I have come across. I have never seen such fine layering like this within a lava/igneous rock.
A fresh surface revealed that it was most definitely lava. We collected a sample as this was not a lava we have seen here before. As we were packing up from sampling, we were faced by a seemingly endless herd of cows. We usually stop and let the cows by. Lucy had other ideas though and we were quickly wandering among the cows.
Sharing a path with a very large herd of cows.
It reminded me slightly of the trek up to Everest Base Camp where we were constantly walking with/through the cows, donkeys, and yaks. While we were walking through the cows Lucy pointed out a Spitting Cobra skin. Apparently it is quite rare for her to be guiding along here and not see a snake. I still can’t decide if I am relieved or disappointed that we only saw the skin. I would quite like to see a snake while here…just as long as I see it from a distance and it isn’t startled by us. I’ve been told they only become aggressive when they feel threatened. After walking along the crater wall for about 20mins Lucy informed us that this was the point she usually turns back at. From here on in it was ‘terra nova’ for all three of us. It was here that we turned off the main track following the caldera wall, and ventured a small way into the caldera to see if it were possible to get to the lava flow we wanted to sample.
Looking down into the caldera from our accomodation. The blue dot is where Lucy's guided walks usually end. The red dot is the base of the lava we wanted to sample. Although as the crow flies this is only about 1km from the track, we had to walk almost double this curving and winding to take the least densely vegetated route and avoid a few steep drops.
For only the second time in the two weeks we have been working here I quickly regretted wearing shorts as we were instantly fighting through the vegetation.
There is a phrase within my favourite poem which reads:
“If you can force your heart and nerve and sinew To serve your turn long after they are gone, And so hold on when there is nothing in you Except the Will which says to them: 'Hold on!'”
I found myself referring to this a bit as we set of through the vegetation. I didn’t like it to begin with, having been told of all the creatures which live here, the snakes in particular, I don’t really fancy being bitten by a venomous snake out here. Particularly knowing there is no road access or rescue helicopters for any assistance to come to you if you did get bitten.
Lucy found my nervousness very amusing, and reassured me saying any creatures would have scattered away on hearing us. I was determined to get to the lava flow, and wasn’t going to let my nervousness get in the way of that. It didn’t take long for my nerves to calm. The fear never really left, but there are only so many bushes you can fight through cautiously before giving up on fear. After almost an hour fighting through the vegetation we eventually made it to the lava flow. We stopped for lunch then collected our samples.
Lucy really enjoyed hammering away at the rocks to collect our sample from this site.
It was time to head back to camp, we just had a long, hot slog to get up and out of the caldera. As we were walking back alongside the walls we did spot a couple of places where there where fractures. I think the first set of fractures was actually cooling joints as the entire face had a columnar jointed appearance.
Some typical columnar jointing - Giants Causeway, N.Ireland. Not all columnar jointing forms as perfectly as this.
Columnar jointing occurs when a flow or sill (lateral intrusion) cools quickly. As the magma or lava cools quickly it contracts creating vertical joints which are perpendicular to the flow. Columnar jointing in plan view looks like honeycomb, due to the hexagonal shape of the columns. As we couldn't see the top surface (plan view) Helen will analyse the measurements we took on these joints and compare them to the measurements we took on the other fractures. If the measurements match then it will have just been fracturing that looks like columnar jointing. If they don’t match then we can interpret them to be columnar jointing.
Foolishly I didn't actually get a picture of the columnar jointing (possibly just fractures), but I did get a picture of Helen measuring the joints.
I really enjoyed today, it was nice to be out walking everywhere rather than being in the car much of the time. We did however seem to choose the hottest day yet to be the most physical and active so far. And so there was only one way to end the day… a very nice and refreshing swim in the pool here at Maili Saba.
