If we want to predict the future of our planet under climate change, we need to better understand what happened on Earth before, even hundreds of thousands of years ago.
New research on the Ethiopian Mountains during the last ice age is helping to achieve this. In addition to answering a few geological questions, he also raised a new one: What created the giant stone stripes on the central Sanetti plateau in the Bale Mountains?
As part of the research, scientists analyzed samples of moraine boulders from the Bale and Arsi Mountains, rocks that were once transported by glaciers.
By studying their physical arrangement and measuring the degree of degradation in a chlorine isotope, they determined that past glaciations would not have been synchronized with other similar stretches of mountains.
(Groos et al., Earth Surface Dynamics, 2021)
“Our results show that glaciers in the mountainous areas of southern Ethiopia reached their maximum extent between 40,000 and 30,000 years ago, several thousand years earlier than in other mountainous regions of East Africa and around the world,” he says. glaciologist Alexander Groos of the University of Bern in Switzerland.
While these mountainous areas are not full of ice today, 42,000 to 28,000 years ago – thousands of years before the most recent period when ice sheets stretched far from the poles – they would have been covered by glaciers. covering up to 350 square miles (about 135 square miles). Researchers say that relatively early cooling and the onset of glaciers are probably caused by variations in precipitation and mountain features.
In other words, temperature was not the only driving force behind the movement of glaciers in East Africa during this time. Such perspectives can help us understand what might happen next and what the likely impact is on biodiversity and ecosystems.
As for the massive stone stripes made of boulders and basalt columns, they were discovered during the research, just outside the area of the former ice cap. The stripes are up to 1,000 meters (3,281 feet) long, 15 meters (49 feet) wide and 2 meters (6.5 feet) deep and have never been seen in the tropics.
(Groos et al., Earth Surface Dynamics, 2021)
“The existence of these stone stripes on a tropical plateau surprised us, because the so-called periglacial reliefs of this magnitude were previously known only from the temperate zone and the polar regions and are associated with soil temperatures around the freezing point,” says Groos .
Another way in which the Ethiopian Mountains are different from their immediate neighbors then, in terms of what fell in the last ice age. Scientists believe that these stripes are the natural result of periodic freezing and thawing of the soil near the ice cap, which would have attracted similar rocks together.
(Alexander R. Groos / Digital Globe Foundation)
However, substantial drops in soil and air temperature would have been needed – and what is less clear is whether this is typical of the way the tropical high mountains cooled at that time or whether it was a phenomenon. regional.
We will have to wait for future studies of other regions to find out, but research offers a lot of possibilities for scientists. Understanding climate change in the tropics is crucial – this is where much of the world’s atmosphere and oceans come from – and it would seem that these mountainous regions may have experienced the last glacial period in a variety of different ways.
“Our findings highlight the importance of understanding the local climate context when trying to draw broader climate interpretations from glacial chronologies,” the researchers conclude in one of their recently published papers.
The research was published in Scientific advances and The dynamics of the earth’s surface.