Over the past 5,000 years, East Africa has experienced a dramatic climate shift, becoming increasingly arid. New research has uncovered an unexpected link between this drying trend and the accelerated rifting of the East African Rift Zone, revealing that the continent may be pulling apart faster than previously thought.
In a study published in November in the journal Scientific Reports, researchers found that the reduction in lake levels in East Africa, particularly Lake Turkana in Kenya, has likely contributed to the speeding up of tectonic plate movement. This discovery highlights a two-way relationship between climate changes and geological processes, as climate change appears to influence plate tectonics—a concept not typically considered in traditional studies of Earth’s tectonic forces.
Christopher Scholz, the study’s senior author and a professor emeritus at Columbia University, explained that while we often think of tectonic activity driving climate changes—such as mountains affecting weather patterns—the reverse is also true. “Mountains build, and that changes the local or regional climate,” Scholz said. “But it can work the other way around too.”
The research focused on Lake Turkana, a 155-mile-long body of water that is a key feature of the East African Rift Zone. Over 5,000 years ago, the lake was significantly deeper, part of the African Humid Period when much of the continent was wetter. Since then, the region has become progressively drier, with lake levels dropping significantly. The researchers used lake-bed sediments to examine ancient water levels and sediment flows, finding traces of small faults and the remnants of ancient earthquakes, which suggest that tectonic activity in the area had intensified.
East Africa is currently experiencing a geological process known as rifting, where the tectonic plate beneath the region is slowly pulling apart. Over millions of years, this could lead to the creation of a new ocean separating Africa into two distinct plates. The deep lakes in the region, including Lake Turkana and Lake Malawi, are the result of this rifting process, which has created a deep valley in the land.
Scholz and his team set out to investigate whether the changes in the lake levels themselves were influencing this tectonic activity. Water has a significant impact on tectonics: much like the weight of glaciers causing land to rise as they melt, the large volumes of water pressing down on the crust beneath the lakes may have been contributing to a slowed rate of fault movement. Once the water levels decreased, the tectonic faults had more room to move, speeding up the rifting process.
The research found that after the end of the African Humid Period, the fault movement in Lake Turkana accelerated by 0.007 inches (0.17 millimeters) per year, in addition to the general rifting rate of 0.25 inches (6.35 millimeters) per year. The team also used computer simulations to determine two key factors behind this seismic speedup. First, the reduction in water pressure allowed the faults more freedom to shift. Second, the decrease in water levels also led to changes beneath the surface: The removal of water from the African Humid Period decompresses the mantle under nearby volcanoes, leading to more melting and, consequently, increased volcanic activity and tectonic movements.
This new understanding of the interplay between climate change and tectonic rifting could have important implications for the future of the East African Rift Zone. As the region continues to dry, it could lead to more frequent earthquakes and other tectonic phenomena. Researchers are now expanding their study to Lake Malawi, where they plan to investigate water level changes over the past 1.4 million years to further explore how climate affects the separation of continents.
Christopher Scholz emphasized the significance of these findings, noting that understanding the effects of large-scale water volume changes in these lakes is crucial in painting a more comprehensive picture of Earth’s tectonic activity.
