A giant 165ft deep crater was discovered by accident after a huge explosion in the frozen Arctic tundra.
It is believed a summer of unprecedented heat led to the blast which was caused by a build-up of methane gas.
The hole – one of the biggest found so far – was found on the Yamal peninsula in Russia as a TV crew flew overhead.
Scientists who examined the site said blocks of soil and ice were flung "hundreds of metres" from the epicentre of the "colossal force", The Mirror reports.
The experts cited a build-up of pressure from methane gas in the thawing permafrost after a record hot summer in many Arctic regions across Russia.
It is the 17th large cylindrical cavity to appear in the past six years, and previous craters have sparked conspiracy theories about everything from UFOs to Kremlin missile tests.
Gas is released in soil that has been frozen for thousands of years but is now defrosting.
The new hole was initially spotted by chance from the air by a Vesti Yamal TV crew en route from an unrelated assignment in July.
A group of scientists then made an expedition to examine the large cylindrical crater estimated at up to 165ft deep.
Scientist Dr Evgeny Chuvilin, a leading researcher at Skolkovo Institute of Science and Technology, said it was "striking in its size and grandeur".
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The crater came about from "colossal forces of nature", he said.
Professor Vasily Bogoyavlensky, of the Russian Oil and Gas Research Institute in Moscow, told the TV station: "This object is unique.
"It holds a lot of additional scientific information, which I am not yet ready to disclose.
"This is a subject for scientific publications."
These craters appear because "gas-saturated cavities are formed in the permafrost," he said.
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A void space is "filled with gas with high pressure" and "the covering layer distends, the thickness of which is five to ten metres [16-32ft] approximately," he added.
Some but not all explosions have occurred in swelling pingos – or mounds – in the tundra when the gas builds up under a thick cap of ice.
Bogoyavlensky has previously claimed that drilling for natural gas in Yamal – a key supplier for Europe – may be a factor in the eruptions.
He is also concerned at the risk of ecological disasters if the explosions occur under gas pipelines, production facilities or residential areas.
Previously, he warned: "In a number of areas, pingos – as we see both from satellite data and with our own eyes during helicopter inspections – literally prop up gas pipes.
"In some places, they jack up the gas pipes… they seem to begin to slightly bend these pipes.”
Russian scientists call the holes "hydrolaccoliths" or "bulgunnyakhs".
They say the study of the phenomenon is at an early stage.
When the mysterious holes first appeared in 2014 there was wild speculation that they were caused by Kremlin missile tests, aliens from UFOs, or that they were man-made as a prank.
In 2017, one of the Yamal craters exploded a second time after scientists noticed signs of a new gas outburst.
It had already been flooded with water when the second blast occurred.
Experts have said the funnels could lead to the formation of new lakes.
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