If you asked what’s the deepest trench on Earth, almost everyone would answer the Mariana Trench. They’d be right – at around 11,000 meters (36,000 feet), the Mariana Trench dwarfs any other oceanic trench out there. But if you asked “what is the deepest continental trench in the world?”, few would be able to answer.
Lying hidden beneath a tomb of ice in Antarctica, a recently-discovered canyon beneath the Denman Glacier plummets a massive 3.5 kilometers (2.2 miles) below sea level, making it the deepest land trench in the world.
The world’s deepest land trench
The trench's depth was discovered only recently, as part of a 2019 study by an international team of glaciologists who set out to map the contours of the Antarctic continental land. The team used ice thickness data from 19 different research institutes combined with masses of radar data to peek beneath Antarctica's ice sheets, a similar methodology to what's been used to study Greenland in recent years.
Reported in the journal Nature Geoscience, the result is the most accurate portrait yet of Antarctica's contours, dubbed BedMachine, which is publicly accessible through the US National Snow and Ice Data Center.
Along with the Denman Glacier – the deepest trench on land – the findings also offered a number of previously unknown topological insights into what lies beneath Antarctica's ice.
"Older maps suggested a shallower canyon [beneath the Denman Glacier], but that wasn't possible; something was missing," lead author Mathieu Morlighem, associate professor of Earth system science at the University of California, Irvine, said in a statement at the time.
Mapping out the canyon helps researchers to understand how the ice sheets may respond to the changing climate and which areas of the ice may be vulnerable.
While it is deep, the trench is by no means in the same league as the deepest points on earth. The prize for the deepest artificial hole goes to the Kola Superdeep Borehole in Russia, reaching an astonishing 12,262 meters (40,230 ft) before it was sealed. This is then followed by Challenger Deep, the deepest point of the Mariana Trench, at 11 kilometers (6.9 miles).