East Africa's Drying Climate May Be Speeding Up the Continent's Breakup
The Earth's ever-changing climate has a profound impact on our planet's geological processes, and a new study reveals a surprising connection between a drying climate in East Africa and the accelerated pulling apart of the continent.
Over the past 5,000 years, East Africa has been experiencing a gradual drying trend. This change, as recent research suggests, might be contributing to the faster breakup of the African tectonic plate. The study, published in the journal Scientific Reports, sheds light on the intricate relationship between climate and geology.
The East African Rift Zone, a region of tectonic activity, has shown increased fault activity since the decline in large lake levels. This finding challenges the conventional understanding that mountains typically influence local or regional climates. Instead, it proposes a reverse causation where climate changes can impact geological processes.
Lake Turkana in Kenya, a vast body of water, serves as a key research site. Its dimensions, measuring 155 miles in length, 19 miles in width, and reaching depths of up to 400 feet, provide valuable insights into the past. However, the lake's water level was significantly higher 5,000 years ago, approximately 500 feet deeper, during the African Humid Period.
During this period, much of Africa was wetter, and East Africa experienced a prolonged period of drier conditions that followed. The researchers, by studying lake-bed sediments, uncovered ancient water levels and sediment flows into Lake Turkana. In the process, they identified small faults and earthquake imprints in the sediments, indicating increased tectonic activity.
The African tectonic plate, underlying East Africa, is in the process of pulling apart, potentially splitting into two plates with an ocean between them. The deep, narrow lakes in the region, including Lake Turkana and nearby waterways like Lake Malawi, are a result of this rifting process, creating a deep valley.
The study's authors, led by Scholz, aimed to understand if the changes in the lakes themselves were influencing this rifting process. Water plays a crucial role in tectonics, and its retreat can lead to isostatic rebound, where the land beneath rises like rising bread. Large water bodies exert pressure on the crust, potentially affecting earthquakes.
The researchers discovered that after the African Humid Period, the faults in Lake Turkana accelerated, moving at an average rate of 0.007 inches per year. In comparison, Africa's general rifting rate is 0.25 inches per year. Computer simulations revealed two primary causes for this seismic speedup. Firstly, reduced water pressure on the crust allows faults to move more freely. Secondly, the removal of water decompresses the mantle under a volcano on an island near Lake Turkana, leading to increased melting and tectonic activity.
This study highlights the intricate relationship between climate and geology, suggesting that climate changes can have a significant impact on the breakup of continents. As the researchers continue their work at Lake Malawi, studying water level changes over 1.4 million years, they aim to further understand the climate's role in continental separation.
