The shrinking of Kenya's Lake Turkana over thousands of years due to a drying climate has led to increased seismic and volcanic activity beneath it. This phenomenon, detailed in a new study, may have affected early human ancestors in the region known as the cradle of humanity. As climate patterns shift globally, similar risks could emerge elsewhere.
Lake Turkana, situated between Kenya and Ethiopia in the Great Rift Valley, is the world's largest desert lake. Nine millennia ago, it was larger and surrounded by lush grasslands and forests. However, between 4000 and 6000 years ago, a drier climate caused water levels to drop by 100 to 150 metres.
This reduction in water pressure on the lakebed influenced underlying geological processes. Researchers, led by Christopher Scholz at Syracuse University in New York, analyzed sediment cores and used sonar imaging on 27 faults across the lakebed. They found that fault slippage accelerated at an average rate of 0.17 millimetres per year as the lake shrank.
"We postulate that there would have been more frequent earthquakes and more frequent volcanic eruptions during these time intervals," Scholz says. "It would have compounded the already difficult conditions that can be observed today in that area."
The study also employed computer modeling, which indicated that lower water mass allowed more magma to rise, potentially increasing volcanism. One of the lake's three volcanic islands erupted in 1888. Ken Macdonald at the University of California, Santa Barbara, notes this as the first clear evidence of such effects around a lake. "It’s almost like loosening the cork on a champagne bottle," he says. "As you decrease that pressure, the magma is more likely to rise up in the crust and erupt."
The region, often called the cradle of humanity, holds fossils up to 4.2 million years old from at least half a dozen hominin species. Early humans there likely faced compounded challenges from drought and heightened seismic risks.
Today, increased rainfall from climate change is raising Lake Turkana's levels, but it would take thousands of years to significantly suppress activity. The authors urge incorporating climate-driven water level changes into seismic hazard assessments and advise seismometer deployment before major hydrological alterations like dam construction.