Aerial overview of Nabuyatom Crater, located south of Lake Turkana, Kenya
Martin Harvey/Alamy
The arid conditions of East Africa have led to a decline in the water levels of Kenya’s Lake Turkana for millennia, triggering rising earthquakes and volcanoes beneath its surface. This risk associated with climate change could potentially impact other water bodies globally as precipitation and drought patterns shift.
Lake Turkana is often referred to as the cradle of humanity. Fossils from at least six different human species, dating back 4.2 million years, have been unearthed here, with some believed to have lived alongside each other. As the size of these lakes decreased over thousands of years, our ancestors faced not just a more arid environment but also increased geological activity.
“We believe that during these eras, there would have been a rise in the frequency of earthquakes and volcanic eruptions,” states Christopher Scholz, a researcher at Syracuse University in New York. “The challenging conditions observable today in the region would have been further intensified.”
Situated in the Great Rift Valley between Kenya and Ethiopia, Lake Turkana is the world’s largest desert lake, a greenish body of saline water surrounded by sandy shrublands and breezy outcrops. However, 9,000 years ago, it was considerably larger and enveloped by rich grasslands and forests.
Between 4,000 and 6,000 years ago, the climate shifted towards drier conditions, causing the lake’s level to fall by 100 to 150 meters. Such a drop in water levels lessens the pressure on the lakebed below, potentially influencing seismic behavior. To investigate the impact of this climatic alteration, Scholz and his team pinpointed specific sediment layers that correspond to various historical periods from cores previously extracted from the lakebed.
They conducted sonar scans from a boat over 27 faults on the lake floor to analyze how the sediment layers were displaced vertically on either side of each fault. Their findings suggested that as the climate grows drier, the sides of faults slip past one another at an accelerated average rate of 0.17 millimeters per year.
“The key mechanism here involves tightening and loosening this deformation area, which causes earthquakes,” Scholz explains. “A drier climate coupled with lower lake loads will facilitate a slicker fault line.”
Computer simulations indicate that as water mass diminishes, an increase in magma movement occurs beneath the lake. One of the volcanic islands in Lake Turkana erupted in 1888.
Research previously demonstrated that declining sea levels heighten volcanic activity at ocean ridges. However, this provides the first solid evidence of a similar trend occurring around this lake, according to Ken McDonald from the University of California, Santa Barbara. “It’s akin to loosening the cork on a champagne bottle,” he remarks. “Reducing the pressure increases the likelihood of magma ascending within the Earth’s crust and erupting.”
While climate change is currently leading to higher water levels in Lake Turkana, it may take millennia for seismic and volcanic activities to stabilize significantly.
Nevertheless, the authors of the study advocate that seismic risk assessments should take into account how climate change affects water levels. Moreover, policymakers should factor in seismic vulnerabilities when planning the construction or deconstruction of dams.
“They should install [seismometers] before making any substantial alterations,” McDonald advises.
topic:
Source: www.newscientist.com
