Well I am back in a chilly Scotland!
Now it is time to sieve through the data, maps and samples. Start putting together some ideas as to what is going on at Menengai on geological terms.
The rock samples are currently in Nairobi. Still? I hear you say. Why? I hear you ask. Well to export rock samples a permit is needed and before that a research permit is also needed. And despite advance applications I am still waiting. The Kenyans are just the most friendly people ever, but there is no sense of urgency. We westerners rush around like headless chickens. The Kenyans? Well things get done when they get done. Thats just their chilled out approach to just about everything.
So what else? Well there are school visits planned and seminars to do. As well as digitise maps and write reports. And of course start to plan the next field season.
Keep following this blog for updates on results, information posts and plans for the next trip!
Lala Salama from Scotland this time!!!
Tuesday, 23 September 2014
Today was the last day in the caldera. The end of our time here has almost arrived. I have had the most amazing time, met some amazing people who I will stay in touch with and the caldera has most certainly been the hardest field location I have worked in to date. I can’t wait to come back next year! I suspect there will be a few tears tonight and tomorrow when we leave. Most of the staff are coming in tonight to say good bye.
Me, Jenny, Florence and chef Samuel. This was a teary good bye, thanks to Flo!
Security check point!
So today was a case of finishing off in the caldera. It is always advisable when doing fieldwork, to allow a day or two of finishing off. It gives you time to revisit locations that may have confused you in some way, or add to the data pool. Anything that you feel the need to readdress. Once you have left you can’t go back!
Firstly, we went to visit Great Rift Drilling’s Rig 1, owned by Cluff Geothermal, now that it is fully constructed. It’s a much smaller set up than the rig we visited on Day 2. Hydraulics are used to control the drill string in this case. It is much more compact, takes 4 days to take down, move and reconstruct; compared to the 21 days for the larger rigs owned by GDC. They also cost a tenth of the cost to move compared with the GDC rigs. The amount of water used is vastly reduced with these rigs as more often than not, air is used to lubricate and to raise drill cuttings to the surface. The only time water is used to excess is when the lithology is very loose or unconsolidated. This is when cave ins, or sluffs, occur within the drilled hole. Mud contributes to keeping the lithology where it is, stopping debris filling the bottom of the hole. In this instance, when the water and mud returns to the surface, it is sieved so it can all be reused. These rigs can drill to 3000m, in comparison to 7000m for the larger rigs. However at Menengai, the maximum depth is 3200m, which was a one off. The rig can also case to 2000m. It is packed with wireless technology, meaning it takes less manpower to work and control and it is overall more accurate. All in all it is a much more cost effective piece of equipment and brilliant with it! There are currently four in the world, so the viability of the rig in this location is being tested. It is an amazing bit of kit, incredibly impressive!
Cluff Rig, Great Rift Drilling 1
Cluff Rig, Great Rift Drilling 1
My remote control toy is bigger than yours! At the drill controls.
While talking to Jeff the rig manager, he told us about a problem they encountered while drilling the proposed well MS-14. They took the drill to 600m and began to cement the hole. But the cement didn’t seem to do its job, it just seem to disappear in to the hole. When he described the cuttings that were coming to the surface it sounded like tuff. The description was brown light weight pebbles, sometimes broken up. It may have been the pumice fall out associated with early stages of tuff deposits. The porosity of this could certainly explain why the cement didn’t do its job. It would also potentially explain why we haven’t seen deposits within the caldera associated with its collapse.
The next task of the day was to return to the fault in the NW corner of the caldera, discovered on Day 10. As access to the caldera walls has been limited I wanted return to this location to try and collect more structural data. More fractures were measured. We also discovered a fault plane that had a different trend to the one measured on Day 10. It had the same pale hardened coating of what is likely to be clay. It also had large slickenlines which were also measured. I am still playing around with what this fault might mean as it hasn’t been recorded in any literature. The different trends of the fault(s) may be because the fault is scalloped and is part of a small collapse of the NW crater. Or it may be two different faults and have nothing to do with any collapse. What we did notice was how unstable the area is. Since our last visit just 9 days ago, more of the cliff has collapsed on to the road making access with the car even harder. So we didn’t spend too much time there.
This was followed with a quick visit to the fumaroles by well MW-10 where we cooked breakfast. I just wanted to collect samples of the altered rock to analyse. We also went back to the second set of fumaroles discovered on Day 13. I wanted to check the surface above the fumaroles to see if there were any emanations higher up. There were small ones that weren’t too hot, the alteration of the rocks was less and they were close to a large fracture that may have been a low energy fissure. There were also elongate depressions along the surface that may be fractures that have not quite propagated to the surface, but the surface trace is due to land subsidence in to the fractures.
I have unexpectedly got involved with Ujima Foundation while here. An amazing charity that gives young men and women from the local communities a chance to train in the hospitality industry. The trainees are usually those who have had a struggle in life and may never have had the opportunity to escape from hardship if it wasn’t for the foundation.
One example of many is found with Lillian. A young hard working woman who loves her job here at our accommodation, Maili Saba Camp. Her father was abusive to her mother, but her mother remained believing her two girls were better in a home with both parents. At 16, her father passed away, a weight had been lifted. A year later her mother passed away also. Lillian was left to support her younger sister and pay for the home. She down sized property, giving her a little money to live on while working at the markets selling products bought from the local farmers. A friend one day mentioned the foundation and got Lillian an interview. Despite forgetting the interview and having to run from the market, then forgetting she still had her apron on, she got the position to train in hospitality with the foundation supporting her.
Tomorrow, we are off to Lake Bogoria, in part a day off, but we won’t be able to help ourselves, we will still find geology to look at. There is little to no understanding as to why the flooding has occurred and Lake Bogoria is not the only lake that has flooded. All the EAR lakes in Kenya have flooded and some in Ethiopia are demonstrating the same. One thought is the continuing stretching and thinning of the crust has resulted in fracture and/or fault propagation downwards in to the aquifers. Hydrothermal fluid contamination has been recorded in two lakes in Ethiopia.
Monday, 22 September 2014
Today we returned to the northern part of the caldera to investigate a deep gulley running almost NE-SW along the caldera wall. According to the contours on the site map, the gulley dropped from an elevation of just over 1800m to just over 1300m and back up again, over a distance of about 200m. First observations of this structure were made from the road on Day 13. From this vantage point the gulley looked like it may have formed during the caldera collapse, where in this area, the core of the volcano detached from the caldera wall during this collpase phase. Both the caldera wall and the opposing wall appear to be steep. The position of the gulley matches that of inferred NE-SW striking faults of Mariita (2013). It also meant we may have another opportunity to observe the caldera walls and potentially collect structural data. The nose of the NW crater flow is also at this location.
The distance to the caldera wall looks much further than it actually was. Jenny was route decider today!
The nearest road was about 800m east of our intended destination. Walking in the approximatly west, the topography had a gentle slope down towards the northwest, with three sudden drop offs every 150m or so. These steep drops were the nose ends of three separate ropey flows we had previously observed in multiple locations across the caldera. They were also easy to climb down with rubbly flow ends forming natural deep steps.
One of the clambers down the lava flows
Almost arriving at the southern side of the NW crater lava flow, we met a farmer, who was a little wary of us. Once our driver had spoken to him about what we were doing he relaxed a little.
On arriving at the location we discovered that the gulley was not quite what we were expecting. Instead of our exciting inference, admittedly made from a distance, the gulley only had vertical walls on the side of the caldera wall. The opposite side of the gulley is made up of nose ends of ropey lava flow lobes, the flow being about 10m think. Sadly there were no structures to measure.
Jenny and I discussed the course of action regarding getting up to the caldera walls. Along large lengths of the caldera wall, there have been landslips, all of which were potentially blocking our route up to the caldera wall. We decided to walk down the sloping topography following the south edge of the lavas from the NW crater and assess the stability of the landslips when we were at their bases. We were just about to leave, when the farmer said something to Vincent our driver in Swahili. Vincent quickly advised us not to go any further as the thick vegetation at the base of the slope is the day time resting place for three leopards.
The above image shows the debris along the caldera wall that has accumulated during recent small scale landslips. The rich green vegetation is leopard home!
From as close as we were aloud to get (our driver worries!) we could see vertical fractures in the caldera wall that had a strike of almost E-W. Again it is this trend of structures that appears to dominate. It was very clear to see at this location, that the collapse phases that occurred directly next to the caldera wall all occurred vertically.
Our day ended earlier than planned today. Sometimes it can't be helped.
Lala Salama from Kenya!
Sunday, 21 September 2014
Some of you reading this may be wondering, Why Kenya? Why this location? Well here is a brief overview
The Kenya Rift Valley is a distinct feature bounded by normal faults in an area of lithospheric thinning. I is a tectonic feature that runs from Lake Turkana in the north to Lake Magadi in the south. It froms a classic graben structure ranging from 40 to 80km wide. The Kenya Rift is part of the bigger East African Rift System, which is an intra-continental divergent margin where the Somali and Nubia plates are rifting apart at a rate of 2cm per year, creating a much thinner crust. Continental rifting has never been observed and although the likely break up of Africa will not occur in our life time, the processes can be observed. Making this a very important region for geologists. The rifting has been accomapanied by volcanism since the late Tertiary, with seravl Quaternary volcanoes peppering the rift floor in Kenya due to the rising of the underlying mantle. Upwelling mantle may melt, rising to the surface using normal faults linked to the deformation and extension, as conduits.
E-W tensional forces have resulted in extension and block rotation. The main rift is bounded by N-S rift scarps. Each side depicts a different type of tectonic style that is thought to indicate crustal detachment. The Molo and Solai TVA’s converge at Menengai and control the geothermal systems here.
Menengai is situated central to this image (http://www.renewbl.com/category/geothermal)
Menengai is one of these volcanoes that litter the rift floor. It is characterised by complex tectonics assocuiated with a triple junction formed by the joining Nyanza Rift with the Kenya Rift. It began life around 200,000 years ago as a trachyte shield volcano with a volume of about 30km3. The caldera collapse began about 29,000 years ago with pumice falls and a single ash flow tuff with a volume of 20km3. A further collapse phase occurred around 16,000 years ago with a with the eruption of 30km3 of magma.
A huge project was undertaken by KenGen to thermally map the caldera which brought to light several hotpots within the caldera. This project has since lead to the Menengai Geothermal Project.
It is estimated that 84% of Kenyans do not have access to electricity. Those that do find it very expensive and unreliable, we had a 10 hour power cut during a thunderstorm just a few nights ago. The locals say it usually happens at least once a week and that we have been quite lucky.
The importance to the local communities and beyond
The Menengai Geothermal Project aims to start generating electricity by the end of next year with a long term forecast to produce enough electricity for 500,000 homes and 300,000 businesses. This project along with the project at Olkaria and the proposed project at Longonot means that in around 15 years Kenya is likely to be completely energy independent, with a cheap and reliable source of electricity.
Menengai Geothermal Project
I feel very fortunate to be working on such an important project. I love being in the field and geology has and always will fascinate me. This project allows me to indulge in volcanology and structural geology as well as geochemistry. It has also given me the opportunity to learn the engineering side of the work being done here. But in addition, I am contributing to a project that will very soon be changing the lives of so many people. I have met some amazing and friendly people. Everyone in the caldera who sees us working, stops to say hello, they are curious as to what we are doing, they want to shake hands and wish us luck. The children always wave to us and we have even had a big cheer at the end of a school day. So many people here have very little, but they are all so happy.
Lala Salama from Kenya!
We are getting close to the end of our time here with only 3 more days in the field left. I at least will be very sad to go.
I have found with fieldwork in the past that as you draw to the end of a trip, regardless of how long that trip might be, the fieldwork tiredness starts to kick in. This trip I have been up early most days (around 6am) checking base maps, site maps, Google Earth (when the internet works!) and LandSat images in order to plan the day. This might sound somewhat last minute, but we have found on many occasions during this trip that the day’s plans can often change last minute. So I go to bed with an idea of the next day’s plan, but organise in the morning.
Our days in the field have varied from around 6 hours to close to 10 hours, with the shorter days usually being the hottest. It’s easy to forget how much the heat can take it out of you. It’s not like sunning yourself on a great beach. It’s hot and very dusty, with a heavy field bag on occasion and walking several kilometres most days, often up steep hills. Don’t get me wrong, I’m not complaining, I genuinely love what I do and hope others may be inspired too.
After each day in the field, we get back, get our things ready for the next day, shower (though our nails get cleaned in the caldera using the high pressure water from the pipes!), work more (blog writing, emails, in my case go over what has been covered on that day), dinner and work a bit more. The day usually ends around 11pm. So as you can imagine, doing that for (currently) 17 days straight and by the time we finish here 20 days, plus 2 days travel, it catches up with you.
Cleaning the fingernails!
So on to today. The plan was to try and locate evidence that indicates that the Solai TVA cuts in to the caldera along the eastern edge. Satellite images show there to be something. But after yesterday, we know this may be inaccurate or a trick of the sunlight. We found a round that would take us between the plantations of maize, corn and bananas. After driving as far as we could we walked a little further until we could see the caldera security gate. Immediately south we could see two outcrops in the cliff face. We could have used an old farmers path to walk across, however, the advise from our driver was that we shouldn’t, because we hadn’t asked for permission. In the UK we have ‘right to roam’ or you would simply ask the land owner. Here you have to ask community elders and often you would be accompanied by one. But it’s not the end of the world. It was still possible to record some approximate data. And should I feel this area needs looking at in more detail on my trip next year, I can make use of the many contacts and friends I have made on this visit, to arrange access next time.
We decided to go back in to the caldera, heading to an area already visited, the south. As we observed on Day 5, there are at least two faults that run north-south from Nakuru to the edge of the caldera. There are many articles available with schematic style maps of Menengai caldera showing these faults, then inferring their continuation in to the caldera.
Referring once again to satellite imagery, it is possible to see where one of the fault traces might be observable. In the same locality there are two very large mounds that we wanted to check out. They sit on a north-south trend and there have been reports of young cinder cones on this trend also. These mounds however, looked to be the northern extent of one of the hummocky terrains. We also went back and observed the glassy scoria type bombs buried in tuff that we observed on Day 9.
For the fault we parked up and walked across about 100m of gently sloping compact tuff covered land to a steep sided gulley, the opposite side there was a dark blocky lava flow. This gulley was on the right trend and in line with what looks to be a fault trace in the distant caldera wall. As this gulley cuts through tuff, there were no slickenlines or other structures that we could measure and record. I know see why the faults with in this part of the caldera have remained inferred. I too would go as far as to infer myself.
The immediate fore-front of the image is the drop off in to the gulley that is a likely location for one of the faults inferred to run from Nakuru to the caldera and in to the caldera.
Our last task of the day was to look at the bombs buried in tuff.
There are several models for caldera collapse: Plate/Piston Collapse – involves the collapse of a whole block in to a chamber along a ring fault; Piecemeal – the collapse of numerous floor blocks due to multiple magma chambers, tectonically controlled faults in the caldera floor or if the entire caldera is a mega breccia; Trapdoor – formed when subsidence occurs in an incomplete ring fault or where subsidence occurs assymetrically in a complete ring structure; Downsag – occurs where ring faults are absent and the rocks overlying the magma chamber deform without fracture; and, Funnel – formed as a result of piecemeal collapse or non-chaotic collapse with a deeper single collapse at the centre and a distinct v or funnel shape.
The general consensus is that Menengai is of the piecemeal style of collapse. The reason we wanted to return to the location where the tuff has buried glassy scoria type bombs is due to the development stages of Menengai caldera highlighted by Lipman (1984, 2000).
The author states the development of Menengai caldera occurred in four stages as follows:
Stage 1: Pre-collapse volcanism; this stage involves frequent surface volcanism that is sometimes explosive, magma accumulation and migration.
Stage 2: Caldera subsidence; collapse associated with large scale magmatic eruptions beginning with a central vent phase, proceeding to a ring vent phase coincident with caldera collapse.
Stage 3: Post-collapse magmatism and resurgence; volcanism is randomly scattered with in the caldera or localise along regional structural trends. A renewed rise of magma results in the uplift or doming of the central part of the caldera.
Stage 4: Hydrothermal activity and mineralisation; often occurring throughout the life of the caldera, dominating late in the cycle developing geothermal systems.
The ash flow tuffs are associated with syn-caldera collapse and the glassy lava flows are post-caldera collapse. Yet here we have evidence of apparently syn-collapse tuffs burying post-collapse glassy lava bombs. The wrong way round when compared to the collapse stages.
The pale rubble immediately above my notebook is a bomb. It's crust has been altered to a clay, but the inside remains a glassy bomb with very large vesicles
Large vesicles at the core of the bomb segments
Our thoughts behind this evidence are: (1) The tuffs within the caldera are not Menengai tuffs, but tuffs from other volcanic activity burying some of the post-collapse bombs of Menengai; or (2) Tuffs have been deposited after a section of the caldera has collapsed. That syn-collapse phase has subsided in to the post-collapse glassy explosive phase producing bombs. While elsewhere another collapse has generated the syn-collapse tuff deposits that are falling at the same time as the post-collapse glassy bombs from an earlier collapse location within the caldera.
Glassy 'scoria like' bombs in tuff
I have previously mentioned that the tuff deposits with in the caldera seem to be quite fine grained for the source to be the location of deposition, even more so as tuff deposits from the collapse have been identified 45km away. But saying that, based on the piecemeal model of collapse, (2) seems more likely.
Tomorrow we plan to visit a steep gulley observed from a distance a few days ago. Keep following to find out what it might be.
Lala Salama from Kenya!
Saturday, 20 September 2014
Well the morning started by a wakeup call from a very noisy bird right outside our tent, followed by fighting (very loudly) between two of the big male baboons. One of the males has been outcast from the troop as he challenged the head honcho and lost. So now he is trying to fight his way back in, and apparently failing!
Head honcho is at the back.
Observations I made of the region prior to coming using Google Satellite, revealed two volcanic craters that have been quite impressively affected by EAR faulting. Sleeping Warrior (aka Split Crater) and another that by all accounts has no name. We visited Split Crater back on Day 3, a volcanic cone that has been cut through the middle by a fault resulting in vertical displacement.
As with Sleeping Warrior, the reason to observe the second crater is because the effect of faulting on Menengai caldera cannot be observed as new lavas bury any evidence of fault traces at the surface. Additionally, as previously mentioned, access to the caldera walls to observe any structures, is impossible.
The second crater is about 2km south of Sleeping Warrior. Using the satellite imagery, this crater appeared to have around 100m of horizontal displacement. I wanted to have a look at this because although faults are very rarely clean cut; and by this I mean a fault that is dominated by vertical displacement will have a horizontal element and a fault dominated by horizontal displacement will have a vertical element, I felt it unusual for the fault to be dominated by horizontal displacement in a region that is rifting. All the faults for miles around display vertical displacement as the dominant faulting mechanism, as would be expected.
So, we drove south along the main Nakuru-Nairobi Road to Gilgil, where we needed to turn off. This is where the fun began. We stopped to ask the locals for directions. As on our visit to Sleeping Warrior, many thought we were talking about Olkaria or Longonot to the south, both of which are being/have been developed for geothermal energy. With the assistance of our amazing driver, we managed to get directions, albeit vague ones. Altogether we stopped for directions four times, with two people joining us for the adventure. We still ended up at the wrong crater! This crater was certainly elusive.
The grey linear structure in this image is the location of the fumaroles as seen from the top of the volcano.
Using the satellite images and a good old trusty compass, we managed to approximately locate ourselves as being one crater west of our intended target. A trek among the zebras and a short climb was now required. Finally reaching the top of the crater shoulder and walking around the crater rim, we were satisfied this was our final destination. Over 2 hours drive and 2 hours walking around, we had found it.
As is the case rarely in geology, it was actually a little disappointing. It is a shield volcano, surrounded by predominantly strato-volcanoes, the crater was very shallow, but the reason for the visit, the horizontal displacement was almost negligible! We did however notice fumarole activity close to the base of the volcano along a large fracture that ran almost north-south, again an expected structural trend.
From the bottom of the volcano, it was possible to get an idea of how flat the rift floor is in places, with the multiple, individual volcanic cones spread across the area.
This image shows just some of the many small cones that scatter th rift floor in this region
However, this does highlight an important point that I have mentioned a few times now. The importance of fieldwork. As geologists we have access to all sorts of imagery and data sets, and most of the time this is very advantageous. But on occasion, they can have the opposite effect. I could have quite easily made an assumption on the basis of the images, that there was more strike slip faulting in the region than maybe first thought. Of course assumptions are not ideal, but sometimes cannot be avoided. But should I have done that and not made the time to visit the location, subsequent reports could have contained information that is actually irrelevant.
Tomorrows work will either be a return to a location we want to observe more within the caldera, or work along the top of the north east caldera wall.
Lala Salama from Kenya!
Friday, 19 September 2014
Geology days are always very varied. Many days you may find the weird and wonderful or unexpected. Other days, like today, they are much easier. We are very close to the end of our time here, so identifying individual lava flows has become a little easier. Today there were no real surprises, the only characteristics observed that were new, were gulleys that look like lava gulleys. This is where lava would have once flowed through already cooled lava, carving a path through and smoothing the gulley edges. There were small hints of flow bands on the gulley sides.
A gulley, likely to have been carved and smoothed by a lava flow.
So today was the final big mapping day, covering the eastern area of the caldera. We had several ropey lava flows to distinguish one form the other, the scoria type lava overlying the ropeys and a very impressive chilled margin.
Checking out a great example of a chilled margin
Now, using colour as a way of identifying something in geology is always advised against. But occasionally it does help. From a distance the base of this lava flow appears to grade from dark to light. Knowing I was looking at multiple lava flows, one over the other, and recalling what I have seen on fieldwork in places such as Cyprus and Cornwall, the graded colouration got me wondering, Is it a chilled margin?
The left of the image shows a dark grey, almost black at the base of a flow, getting paler upwards.
The base of the chilled margin is almost glassy, grading to fine grained (can just see with a hand lens) to the smaller end of medium grained. This image does not do it justice.
How can this 'on the ground' work be used? Well seeing it allows a geologist to get a much more accurate impression of the area. Images and data are great, but I've said it before and I'll say it again, there is nothing like being in the field.
What we have been able to establish is that the lower down the stratigraphy the narrower the ropes are. Something you wouldn't get from data or satellite images. The scoria type lavas that overlie the ropeys in all examples. are likely to have been a high viscosity flow and the blocky appearance is due to the cooled flow being brecciated by the energy of the flow behind it.
We can establish the sequence of flows and chemical analysis of samples from different flows will allow geochemists to at least being to unravel what is going on in the subsurface based on the composition of the different flows. And where there is enough feldspar, dating the flows can also be accomplished.
Tomorrow we are off to look at the affects of horizontal displacement on a volcano.
Lala Salama from Kenya!