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Climate change is accelerating continental rifting, the geological process where landmasses slowly pull apart. According to a new study in the journal Scientific Reports, the East African Rift System (EARS) became more tectonically active after its major lakes shrank due to a drier climate 4,000 to 6,000 years ago. This could have caused more frequent earthquakes and volcanic eruptions.

The research team, led by scientists from the University of Auckland and Syracuse University, studied the Lake Turkana Basin in northern Kenya. This region is ideal for analyzing how climate and tectonics interact because it lies within the magmatically active eastern part of EARS and has witnessed dramatic lake-level shifts.

Investigating fault activity

Scientists examined 27 underwater faults by comparing two time periods in the South Turkana Basin. The first was the wetter Late African Humid Period (9,631鈥�5,333 years ago) and the second was the Post-African Humid Period (5,333 years ago to present), when the climate was much drier. Using geological data and computer models, they calculated how the reduced weight of the lake water affected fault activity.

The researchers discovered that the speed of faulting in the EARS accelerated significantly after the region's major lakes shrank, showing a mean increase of 0.17 mm/year in their slipping rate. "We provide the first empirical evidence of increased fault activity in response to climate-induced lake level changes in the East African Rift System over time scales of 10鲁鈥�10鈦� years and reveal that climate-tectonic interactions are enhanced in magmatically active rift systems."

Reducing pressure on the crust

The study authors suggest a two-part mechanism for how the drop in lake water affected the forces accelerating drifting. The immediate effect was the removal of weight from Earth's crust. For example, when Lake Turkana's level dropped by 100 to 150 meters, it reduced pressure on the faults, making them more likely to slip. It is similar to a heavy bowling ball being taken off a mattress, with the surface springing back up.

The most significant effect was that the reduction in the weight of the lake decreased pressure on the mantle (the layer below the crust). This caused more rock to melt, sending magma into a chamber beneath the South Island volcano. The chamber grew like a powerful underground balloon, further accelerating fault movement. When the scientists ran computer models, they found that this magma pressure was the dominant force accelerating the faults.

This latest research is an important reminder of how climate change can affect deep geological processes. These insights could inform infrastructure planning and risk management in regions near lakes, especially decisions concerning dams and other large water projects.

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