A previously unknown canyon has been discovered in Greenland, hidden beneath the ice. It is at least 750 kilometres long. To put that in perspective, imagine a ten kilometre wide gorge, up to 800 metres deep, running from the Southern coast of England and into Scotland. This is on the same scale as parts of the Grand Canyon.

Jonathan Bamber, who led the research, was originally mapping Greenland’s bedrock, which was previously thought to be relatively flat and smooth. “Unexpectedly, we found an enormous apparent formation,” he said. “We looked at it in more detail, and realised it was a canyon.”

The canyon, which is thought to predate glaciation, has remained hidden beneath two kilometres of ice for more than four million years. It has the characteristics of a meandering river channel, an ancient river system that Bamber thinks hasn’t been significantly modified by ice cover.

It is almost twice the length of the Grand Canyon, half as deep but almost as wide, and certainly the only feature in Greenland this long…

“This really is quite remarkable,” Bamber said. “In an age when you have Google street view covering the entirety of the inhabited world, when virtually every house is mapped. In this context, to discover a geological feature of such scale is astonishing…”

“We think the canyon is an efficient conduit for ice-melt from the glacier. If you want to model glacial movement – something that is ever more crucial due to global warming – then knowing about such topography is very important.”

The discovery shouldn’t affect our forecasts for future sea level in itself, but it does highlights that we still don’t know everything about the surface of our own planet.

Unexpected discoveries always lurk in the back of the mind of any researcher. It surely is a gas when something like this pops into focus and changes from anomalous shadow to a discrete discovery.