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Falling water levels at Lake Turkana in northern Kenya altered the stresses in the Earth’s crust and coincided with more active faulting, according to a new Scientific Reports study led by James Muirhead from the University of Auckland with collaborators at Syracuse University.
The team links a long-term lake drop of roughly 100–150 meters over the past ~6,000 years to measurable increases in fault slip rates within the East African Rift System—a vast tectonic zone where Africa is slowly splitting apart.
Researchers examined “fault throw rates” (the speed at which one side of a fault drops relative to the other) on 27 faults beneath Lake Turkana. Comparing two windows—the late African Humid Period (9,631–5,333 years before present) and the drier post-Humid period (5,333 years ago to present)—they found an average increase of 0.17 ± 0.08 mm/year, with 74% of the faults showing higher post-Humid throw rates and only 11% showing decreases.
Lake Turkana itself is about 250 km long and up to 30 km wide, with mean and maximum depths of 30 meters and 120 meters today.
The study argues that when lake levels fall, the crust “lightens,” easing pressure on faults so they can move more readily. Numerical models show two reinforcing drivers of stress changes on the faults:
Lake unloading from the 100–150 meter drop, which reduces vertical load on the crust.
Magmatic effects from enhanced mantle melting as pressure declines, which can raise pressure in a mid-crustal magma body and further nudge faults toward failure.
In these simulations, magmatic loading can generate Coulomb stress changes (a measure of how close a fault is to slipping) up to ~650 kPa, larger than the ~95–230 kPa expected from lake unloading alone.
The authors therefore suggest magma-related processes likely dominate the stress increase during low-lake stands.
The work provides the first empirical evidence for climate-driven increases in fault activity within the East African Rift, complementing earlier research in Iceland and the western United States, where loss of ice mass was linked to more tectonic and volcanic activity.
Here, the mechanism is hydrological—lake level change—acting over thousands of years, not human timescales.
While Muirhead noted that “surface processes—like climate and rainfall—also play a role,” the paper emphasizes that any effect on volcanic or tectonic activity unfolds on geological timescales.
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