Thursday, 11 September 2014

Day 5 - A Perplexing Day in the Caves

Standing at the highest point of the caldera, I listen to Daniel our guide, telling me how Menengai is Masai for 'Mass Death'. Named because of the amount Masai Tribe members who perished during an eruption. The area was used during the wars as a look out point also.

Most of the caldera can be viewed from this point, 2272 m.a.s.l. Below my feet is the deepest collapse of 485m. The source of the young lavas can be seen clearly from this point, a cinder cone situated central to the caldera.

Panoramic from the top of the view point, eruption centre towards the middle

A couple of miles to the west of the view point, Daniel showed me the caves. But enroute, he pointed out the flooding of Lake Nakuru, with hundreds of trees surrounded by water. This flooding event has been observed by the locals across Kenya, affecting all the lakes of the Kenya Rift. The lake has risen an estimated 2m in 2 years. As the average rainfall in the region is 910mm, run off from the rift flanks is not enough  to explain the flooding. A similar occurrence has also been observed in some areas of Ethiopia. Initial analysis of the lake waters in Ethiopia show there to be hydrothermal contamination. This suggests that beneath the water there is a structure that is being exploited as a conduit for water to rise from depths to the surface. Wok is required in this field of study.

The first cave was a bit of a puzzle to start. The opening dips north towards the caldera and the access is through a small fracture at one side. Once inside, the deposits can be seen in cross section. There are tuff deposits overlain by lavas, further overlain by another tuff deposit.

Lower tuff overlain by lava.

The opening to the sky is about 20m wide, with lava tubes in the walls. 

The positioning of the opening on the southern flank would result in the opening dipping towards the south. The dip north indicates that this was a flank crater prior to the caldera collapse, the collapse has not only cut through the flank crater but the vent also, dropping its northern side more than its southern side.

The second crater is much clearer and larger at 100m across. A second eruptive centre on the southern flank, but further south than the previous one. This location has been unaffected by the caldera collapse. a steep climb down leads to a cave at the northern edge. Despite being only 200m south of the first crater, there is no evidence of tuff deposits in the walls.

It's steeper than it looks. Honest!

The entrance to the cave was about 2.5m high and 10m across. Inside it narrowed slightly then opened out to about 30m across and 10m high. Up to a height of about 2m there was evidence that the chamber had in part contained molten lava, with 'drips' on the underside of overhangs. As there is only one way in and out of the cave, the only possibility is that there has been overspill from the lava lake on occasions.

Leaving the crater behind, walking just a few hundred meters to the west, there was a steep, narrow gully with a dip of about 65 degrees to the east. A fault with normal, vertical displacement of about 3m. The fault extends almost all the wat to the town of Nakuru about 7km away to the south, up to the crater edge. inferences have in the past been made that this fault and another one just to the east, cut through the caldera, possibly the entire diameter of about 12km, linking in to the Molo TVA to the north west. However, young lavas currently bury any evidence of this and geophysics are unclear. 

The final cave was just a few meters to the west of the fault. a small opening created by a collapse, resulting in access to a tunnel. A lava tube! Evidence of flow and drips could be easily seen from the entrance. Although it is possible to safely enter the cave, I remained at the opening as hyenas hasd been reported in the area and I have heard them 'laughing' at night. People do enter the cave t explore it, but with an armed guard.

Entrance to cave 3

Keep reading. Tomorrow more sampling of lavas, they won't win this time! Lala Salama from Kenya!

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