Lake Challa on the border of Kenya and Tanzania. Photo courtesy of UH

Lake Challa on the border of Kenya and Tanzania. Photo courtesy of UH

Researchers from all over the world, including from the University of Hawai‘i, gathered in November at a beautiful but unassuming volcanic lake in East Africa with the hope of uncovering its hidden record of the climate history so intimately involved in the development of our species, as reported by UH.

In collaboration with the International Continental Scientific Drilling Programme, an international team of Earth scientists, including postdoctoral researcher Christian Wolff from UH Mānoa and the International Pacific Research Center, deployed a floating drilling platform on Lake Challa to recover and analyze a complete core profile of its 210-meter thick sediment record.

The Field Site

International Continental Scientific Drilling Programme drilling rig gathering cores on Lake Challa. Photo courtesy of UH

International Continental Scientific Drilling Programme drilling rig gathering cores on Lake Challa. Photo courtesy of UH

East Africa is known as the cradle of humankind. The unusual geology and climatic conditions of East Africa created periods of highly variable local climate, which, it has been suggested, could have driven hominin evolution and migration out of Africa.

Sediments on the bottom of Lake Challa, a 92-meter deep crater lake on the border of Kenya and Tanzania near Mt. Kilimanjaro, contain a uniquely long and continuous record of past environmental change in East Africa.

The near-equatorial location and exceptional quality of this natural archive provide great opportunities to study tropical climate variability at both short (inter-annual to decadal) and long (glacial-interglacial) time scales, as well as the influence of this climate variability on the region’s freshwater resources, the functioning of terrestrial ecosystems and the history of the East African landscape in which modern humans (Homo sapiens) evolved and have lived ever since.

In support of this drilling project over the past several weeks, innumerable helicopter trips and countless porter traverses were required to carry drilling and scientific equipment (heavy tubing, drill mud, cables, hydraulics) into the crater and out to the barge on the lake. Physically carrying the equipment was made more challenging by the steep slopes of the crater and the absence of a decent pathway. The drilling itself took about three weeks and successfully yielded a continuous profile of the full, 215-m thickness of the lake’s sediments.

Sediments Speak to the East African Climate