Sunday, 14 September 2014

Day 10 - Today Cannot be Faulted, We Found a Fault!

Last night I heard the hyenas and the monkeys and I am currently sitting writing this listening to natures chorus of crickets, bats and some night birds.

Another gloriously sunny day and the temperature is rising daily.

Today we are continuing with mapping by following the roads, but heading towards the west side of the caldera. An unintentional stumble upon workers starting to install electrical cables close to MW-19, prompted a query, Is a rig on the move to well MW-19? Yes it is!

On our visit to MW-09 on day 2, we were told that a rig and everything that comes with it, can be dismantled, moved and rebuilt at a new well location in 21 days. Which when you see exactly what that entails, is very impressive. The rig that is on the move is Great Rift Drilling Rig 1. I hoped to catch a daily record of the rig being dismantled and at least some of the reconstruction at its’ new location. However, it looks like the rig has already come down. So I hope to record it going up over the remaining 10 days or so. I will keep you posted.

Boundary mapping of lava flows can get quite complicated when you have multiple flows, in different directions, often obscured by dense vegetation and can’t be climbed on for reasons of safety. So a large amount of today was spent walking along roads, at every 100m, stopping, locating our position, taking a baring towards the flow being mapped, estimating how far it is away from said location and noting its trend and where possible, flow direction (and dodging the cows!). But in many cases it also involved trying to establish whether flows were the same but having changed direction. Or alternatively, do they appear higher/lower because they are different flows or because they have followed topography.

One of many herds of cows

Ropey lava of two flows were identified along with a much younger but darker flow that is very blocky and broken up. The ropey flows are usually fairly easy to climb over and investigate in some detail. It is these younger darker flows that are dangerous. They are very high, steep sided, sometimes almost vertical. It’s estimated that the young flow observed in the north west of the caldera ranges in height from 30m to 50m and if like others we have attempted to climb, it is likely to be very unstable and home to venomous snakes.

Ropey Lava. The flow covered a large area and split in to three different flows.

The source of this flow is the NW corner where there is a small crater. This began life as a flank crater to the 200,000 year old shield volcano that is now Menengai caldera. 

Entering the lava field at the NW corner of the caldera

The collapse of the volcano also caused the collapse of a section of the craters rim, allowing for lava from this eruption centre to flow in to the caldera. This part of the caldera is very quiet. A road has been constructed but no drilling related work has yet started and as we walked further west along the road, found that there had been a few small rock falls, one of which seemed to still be moving a little. The only living things using the area are the lizards and the monkeys. 

A red blue lizard that turned his back just as I snapped

Walking along the road immediately to the south, just a few meters away from the road, 1m up and accessible, we found a pale coloured surface. It stood out because we were among such dark lavas. Closer inspection revealed slicken fibres and slicken lines. Brilliant! We have finally found a fault that we can gain access to and record some data. Yes, we are in a very tectonically active region. But here everything has been buried by young lavas and the faults haven’t moved much (if at all) since. Walking further, we found that a large section of the lava flow normally very blocky and full of gaps, became a smooth surface. More slicken fibres and slicken lines confirmed that this was a continuation of the fault. The data supports this as a normal fault with an E-W trend. It is difficult to estimate the offset from essentially with in the fault. The fault could be seen in the distance cutting through the wall of the flank crater. It is likely the pale surface where the fault plane was first observed is clay that has hardened over time. The source of this is likely to be feldspars with in the lavas. The heat generated due to friction along the fault plane when a fault moves, will cause alteration and water that would have flowed along the fault at a time in the past would have collected and deposited the clay on the plane. It may have formed a clay gouge that no longer exists as the road has been constructed along the fault.

Jenny has spent the day whistling the whistle call from The Hunger Games. We hear the Mocking Jays, she is determined to teach them the call from the film before we leave. One smart bird managed three notes. We finished they day munching on street corn. A giant corn on the cob, harvested from the crops near by. It is cooked dry in a fire and tastes like popcorn, but with out the calories!

Lala Salama from Kenya.

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