Researchers have revealed a close link between climate change in East Africa and the accelerating fracturing of the continent, indicating that droughts that have persisted for thousands of years may be contributing to reshaping the region's geological map.
The study showed that the pace of rifts in the East African Rift Valley has accelerated since the decline in the level of the Great Lakes, most notably Lake Turkana in Kenya.
Christopher Schultz, lead author of the study and professor emeritus of geology and physics at Columbia University, explained that these results highlight the reciprocal relationship between climate and tectonic plate movement, noting that the influence does not only flow in one direction from geology to climate, but the reverse may also occur.
The researchers conducted their study in Lake Turkana, which is approximately 250 kilometers long and 30 kilometers wide, and currently reaches a depth of 120 meters in some areas. However, its water level was much higher more than five thousand years ago, when it reached a depth of about 150 meters.
This is due to what is known as the African Humid Period, which extended in East Africa from about 9600 to 5300 years ago, when the region was much wetter than it is today, before entering a long period of drought that lasted thousands of years.
During the analysis of the lakebed sediments, researchers were able to determine ancient water levels and sediment flows, and they also detected traces of small faults and ancient earthquakes, providing clear evidence of increasing tectonic activity.
The tectonic plates in East Africa are gradually moving apart, which could eventually lead to the continent splitting into two plates separated by an ocean. Deep, narrow lakes, such as Lakes Turkana and Malawi, are among the most prominent results of this ongoing geological process.
The research team sought to determine whether changes in water levels affect the speed of this cracking, based on the fact that water plays an important role in putting pressure on the Earth's crust, just as happens when glaciers melt and the land rises afterward in what is known as isobars.
The results showed that after the end of the wet African period, the faults began to move at a faster pace, at an additional rate of 0.17 millimeters per year, while the overall rate of African faulting is about 6.35 millimeters per year.
Based on computer simulation models, the researchers concluded that this acceleration is due to a decrease in water pressure on the Earth's crust, which allowed the faults greater freedom of movement, in addition to an indirect effect related to volcanic activity south of Lake Turkana.
The researchers explained that the receding water relieved pressure on the mantle beneath one of the active volcanoes, leading to increased melting rates and the movement of magma into the volcanic chamber, which contributed to enhancing tectonic activity in the surrounding areas.
Schultz said: "We are seeing a marked increase in fault activity during this period, which suggests that earthquakes have become more frequent than they were 8,000 years ago."
The scientific team is currently continuing to study changes in water levels in Lake Malawi over 1.4 million years, in an attempt to gain a deeper understanding of the impact of climate on the breakup of continents.
Schultz concluded by saying, "This data is a key element in building a comprehensive picture of the relationship between climate and the Earth's geological structure."
