Gregory Rift

[6] The first well-known European geologist to explore the region was Joseph Thomson, a member of an expedition in 1879–1880 sponsored by the Royal Geographical Society of Britain.

[7] In 1913 the German geologist Hans Reck made the first European study of the strata in the Olduvai Gorge to the west of the Crater Highlands.

Leakey began exploring Olduvai in the 1930s and collecting material that has led to the site being recognized as an important center of early hominin occupation.

[8] Volcanism and rifting started in Kenya in the northern region of Turkana between 40 and 35 million years ago and then spread north and south.

[9] Volcanism from the Middle Pleistocene onward formed a chain of volcanoes along the floor of the rift throughout its length, dividing it into separate valleys.

The alignment of rows of small vents, cones, domes and collapse pits in the Suswa, Silali and Kinangop Plateau regions support this theory.

However, data from oil and gas exploration wells in Kenya, vents in volcanic shields to the east of the rift at Huri Hills, Mount Marsabit and Nyambeni Hills and recent small cones at Suswa and east of the Silali caldera all indicate that the minimum horizontal stress direction has changed to NW-SE within the last half million years.