This huge pit is growing at an alarming rate. BBC Earth columnist talks about a crater formed in the Siberian permafrost.
Not far from the Yana River basin, amidst a vast permafrost zone, there is an impressive tadpole-shaped sinkhole in the earth's crust. This is the Batagayka crater.
It is also known as the "megadepression" and is the largest formation of its kind: it is 1 km long and 86 m deep. And the crater continues to grow rapidly.
It enjoys a bad reputation among the locals - they call it nothing more than "the gate to hell" and prefer not to be here. But for scientists this place is of great interest.
By examining the layers of soil that were exposed during the formation of the depression, one can understand how our world looked like in the distant past and what climate reigned then.
At the same time, the further rapid expansion of the crater is clear evidence of the impact that climate change has on permafrost.
There are two types of permafrost. The first is formed from glacial ice buried underground, left after the last ice age.
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The second type is ice formed directly in the soil layers, and it is in such permafrost that the Batagayka crater is located. Often, this ice is under a layer of sedimentary rock, and its age is at least two years.
The Batagayka Crater reveals to us a section of the underground permafrost, a certain part of which was formed many thousands of years ago.
The first of the chain of events that led to the formation of the crater occurred in the 1960s. Due to the rapid deforestation, tree crowns stopped covering the ground during the warm summer months, and the sun's rays began to gradually heat it.
All this was aggravated by the lack of moisture, which previously cooled the air and soil, evaporating from the leaves of now extinct trees.
"The combination of these two factors - the lack of shadow and evaporation - has led to a heating of the earth's surface," - says Julian Marton of the University of Sussex (UK).
As a result, the soil layer located directly above the permafrost began to heat up, which led to its melting. From the very beginning of this process, the rate of melting has gradually increased.
That is why scientists are closely monitoring what happens to the crater.
One study, published in the journal Quaternary Research in February 2017, says that analyzing the layers that have been discovered will provide information on climate change over 200,000 years.
Over the past 200,000 years, the Earth's climate has changed several times, relatively warm interglacial periods were replaced by cold glacial periods.
The sedimentary layers at Batagayk "are a continuous geological record, and quite unusual," says Marton. By “reading” this chronicle, scientists will be able to learn how the local climate and environment have changed.
"We're still working on the chronology," notes Marton. The next step will be the collection and analysis of sedimentary rocks.
Ideally, they should be drilled through to create a “continuous sedimentary series” that will allow for more accurate dates.
The data obtained from the analysis of permafrost can then be compared with other temperature data, including the characteristics of ice cores taken from ice sheets.
“We want to find out how much the climate [in Siberia] has changed during the last ice age and how often periods of warming were followed by periods of cooling compared to the North Atlantic region,” says Marton.
This is important, since little is known about the climatic history of a huge part of Northern Siberia. By understanding how the environment has changed in the past, scientists will be able to predict similar changes in the future.
For example, 125,000 years ago, the Earth was in the interglacial period, during which the temperature was several degrees higher than it is now.
“If we can understand what the ecosystem was like at the time, we can get at least a rough idea of how the environment might change with global warming,” says Marton.
If permafrost reacts to warming in the same way as it did after the last ice age known to us, we can expect the emergence of new depressions, large pits and lakes.
In addition, it is possible that new land plots will appear, which are now under the ice at a depth of 10-20 m.
“The permafrost, which is very rich in ice, starts to melt from top to bottom, the ice disappears and a completely new landscape forms,” says Marton.
All this may be just around the corner. We now know that changes in permafrost are happening very quickly.
Frank Gunther of the Alfred Wegener Institute in Potsdam, Germany, and his colleagues have been observing the site for 10 years, using satellite imagery to determine the rate of change.
Over the entire period of their research, the wall in the upper part of the crater grew on average by 10 m per year. In warmer years, even faster changes were observed, up to 30 m per year. Gunther spoke about this at a meeting of the American Geophysical Union in December 2016.
He has reason to believe that in the coming summer months, the sidewall of the growing crater will reach the neighboring erosional plain. This will most likely become another factor in its further increase.
“Generally speaking, over the years we have not seen a sharp increase or decrease in this rate, the crater is growing steadily,” says Gunter. "And the constant growth means that the crater gets deeper every year."
This could have other troubling consequences as well.
Numerous deposits of ice formed during the last ice age are coming to the surface today. This ice in the soil contains a large amount of organic matter, including carbon, which has been stored in it for thousands of years.
“The total amount of carbon in permafrost around the world is comparable to that in the atmosphere,” says Gunther.
The more permafrost thaws, the more carbon is released from it, which is consumed by bacteria, producing methane and carbon dioxide as by-products.
These greenhouse gases are released into the atmosphere, increasing the rate of warming.
“We call this positive feedback,” says Gunther. “Warming is accelerating warming, and similar processes can occur elsewhere.”
“It's not just infrastructure that is threatened. Nobody can stop it. There is no technical solution to interrupt the formation of these craters,”he explains.
There are no signs that the erosion of this crater will slow down anytime soon, as it only grows from year to year.
Therefore, the future of Siberian permafrost is a big question.
