Loisaba Rocks! (Part II)

Abigail explains:

"The next major event in East Africa’s geological history after the formation of the Mozambique Belt,  was the opening of the Great Rift Valley approximately 20 million years ago. Unimaginable forces tore apart the Earth’s crust creating a North-South depression bound by deep faults. Vast quantities of lava were produced in the base of the valley and around 12 million years ago the Rift filled up completely with a particularly hot and runny lava called phonolite. The volume of lava was so great that it overflowed the flanks of the rift - and being so runny it found river courses to flow down and pooled out onto plains. The vast, mostly flat, Laikipia Plateau is underlain by three layers of phonolite as the Rift filled and overflowed three times over a relatively short period of time. Phonolite is well-exposed on the Loisaba escarpments. It is extremely hard, fine-grained, dark grey in colour and with large white rectangular feldspar crystals up to 5cm long. These feldspars would have crystallized in the liquid magma and flowed within it and actually can be used to interpret flow-direction as linear crystals will align parallel to flow. The lava flows are thin, mostly less than 20m thick and act like a hard resistant cap above the underlying Mozambique Belt rocks.

Phonolite was been used throughout Kenya by early man to fashion hand axes and smaller blades as it fractures to give a sharp edge. On Suyian Ranch, next door to Loisaba Conservancy, there are graves close to the flow edges where the upper surfaces have fractured to produce rocks the size that can easily by carried by one person. Elsewhere rock art and cave shelters indicate that humans have inhabited this area since the Neolithic.

Looking up at the Maabarti Cliffs 
Maabarti is Swahili for 'corrugated'

...and looking through the Maabarti rocks

A safari along the Maabarti Cliffs, setting off from Kiboko Star Beds takes up to eight hours.