The draining of the Aral Sea has triggered a profound response in the Earth’s upper mantle, lifting the sea bed by an average of 7 millimeters per year. A groundbreaking study reveals the deep-seated consequences of human activity on our planet.
As the Aral Sea has been drained by irrigation and dried up, the mass loss on the surface has caused Earth’s upper mantle to rise up, lifting the emptied sea bed an average of 7 millimetres per year.
The Aral Sea in central Asia was once one of the world’s largest bodies of water, covering almost 70,000 square kilometres. However, Soviet irrigation programmes starting in the 1960s, as well as later droughts, emptied the sea. By 2018, it had shrunk by almost 90 per cent and lost around 1000 cubic kilometres of water.
Once the world's fourth-largest lake, the Aral Sea has shrunk dramatically since its peak in the 1960s.
Its water level dropped by over 23 meters due to Soviet-era irrigation projects that diverted water from the Amu Darya and Syr Darya rivers.
The sea's surface area decreased from 68,000 square kilometers to less than 10% of its original size.
This has led to severe environmental consequences, including the loss of fish populations and increased salinity levels.
Researchers Wang Teng at Peking University in China and Sylvain Barbot at the University of Southern California used satellite measurements to track subtle changes in the emptied sea’s elevation between 2016 and 2020. Although much of the sea’s water disappeared decades ago, they found the uplift is ongoing, with the surface rising by around 7 millimetres per year on average.
The team then used a model of the crust and mantle beneath the Aral Sea to test what changes deep below would lead to this observed pattern of uplift. According to their findings, the observations are completely compatible with a deep response to this change. The unbending of the shallower crust created space, which viscous rocks in the upper mantle wanted to flow into.
Rebound in the upper mantle is known to occur after other large changes in mass at the surface, such as the advance and retreat of glaciers. However, the response to the draining of the Aral Sea may well be the deepest example of a human-caused change in the solid Earth. The uplift beneath the Aral Sea also offers an unusual opportunity to estimate small differences in the viscosity of the mantle, particularly where it lies beneath the interior of a continent.
The Earth's mantle is a vast, rocky layer beneath the crust, comprising about 84% of the planet's volume.
Human activities have significantly impacted this region through drilling, mining, and volcanic eruptions triggered by human actions.
For instance, oil and gas extraction has led to the injection of fluids into the mantle, altering its composition and potentially causing earthquakes.
Additionally, the injection of CO2 into the mantle for carbon sequestration may also have unintended consequences.
In addition to illustrating the sheer scale of human activity, the uplift beneath the Aral Sea provides valuable insights into the effects of environmental disaster. It also highlights the importance of understanding plate tectonics and the behavior of the mantle beneath continents.
Environmental disasters are triggered by human activities, climate change, and natural phenomena.
Deforestation, pollution, and overexploitation of resources contribute to devastating effects on ecosystems.
Rising sea levels, intense storms, and droughts have severe consequences for biodiversity, human settlements, and economies.
According to the United Nations, environmental disasters result in $1 trillion in economic losses annually.
Understanding these causes and effects is crucial for developing effective strategies to mitigate and adapt to environmental challenges.
- newscientist.com | Earths upper mantle is revealing the deepest effect of human activity
