Over the past 5,000 years, East Africa has experienced significant drying, and interestingly, this change may be causing the land to separate more rapidly. A recent study published in Scientific Reports reveals that the decrease in large lake levels, particularly around the East African Rift Zone, has accelerated geological faults in the region.
Christopher Scholz, a geologist and professor emeritus at Columbia University, emphasizes a surprising link between climate and the movement of tectonic plates. “It’s often thought that changes in landforms affect climate,” he explains, “but the reverse can be true as well.” The research team specifically examined Lake Turkana in Kenya, which has shrunk considerably over millennia. Once much deeper, the lake now stands 400 feet (120 meters) deep, a stark contrast to its ancient depth of 500 feet (150 meters) during the wetter African Humid Period, which spanned from about 9,600 to 5,300 years ago.
Researchers explored sediment layers at Lake Turkana to reconstruct past water levels and identified signs of ancient earthquakes. Their findings reveal that the tectonic plate beneath East Africa is slowly splitting apart. This rifting may one day create a new ocean, as deep lakes like Turkana and nearby Lake Malawi emerge from this ongoing separation.
Scholz and his colleagues sought to understand if the changing water levels influenced the rifting process. When glaciers melt, the land beneath can rebound, a phenomenon known as isostatic rebound. Similarly, the weight of water in large lakes can impact the crust. As the water recedes, faults may move more freely.
After the African Humid Period ended, Lake Turkana’s faults began shifting noticeably faster, averaging an increase of 0.007 inches (0.17 millimeters) per year. In general, the whole of Africa is rifting at about 0.25 inches (6.35 millimeters) annually. Computer models suggest two main factors behind this speedup. First, with less water pressing down, the faults gain more movement freedom. Second, a volcano near Lake Turkana influences the activity; the retreat of water decompresses the mantle, leading to more volcanic activity and, consequently, more tectonic shifts nearby.
Scholz elaborates, “We see more intense faulting now than we did 8,000 years ago, which likely means stronger earthquakes in the region.” This ongoing research, particularly a new project at Lake Malawi examining changes extending back 1.4 million years, aims to deepen our understanding of how climate variations can impact tectonic processes.
The study highlights how significant shifts in water levels can shape geological events, reinforcing the interconnectedness of climate and geology, a topic that is gaining attention in scientific discussions. These findings are not only crucial for understanding East Africa’s geological future but also offer insight into the potential impact of climate change on tectonic activity worldwide.
For more insights, check out the full study in Scientific Reports.
