Drumroll, please ... for the glacial drumlins of Namibia
These rock formations are often found in colder climates, so how did they end up in a southern African desert?
As the temperatures soar to the mid-30s this week in the desert of northwestern Namibia, it’s probably hard to imagine the landscape was once covered in ice.
But two US geologists have just surprised themselves, and everyone else, with the disclosure that the world heritage site of Twyfelfontein was shaped by glaciers.
“This is a great example of a fundamental discovery and new insights into the climatic history of our world that remain to be discovered,” said Tim Carr, chairperson of the geology and geography department at West Virginia University.
The discovery was made by Graham Andrews and Sarah Brown, who were exploring the Kunene region northwest of Windhoek when they came across a flat desert studded by hundreds of long, steep hills.
“We quickly realised what we were looking at because we both grew up in areas of the world that had been under glaciers, me in Northern Ireland and Sarah in northern Illinois,” said Andrews, an assistant professor of geology.
What they were looking at was drumlins, which are a type of hill often found in glacial landscapes – but not in deserts.
After returning to the US, Andrews began researching the Namibian drumlins, only to learn they had never been studied.
“The last rocks we were shown on the trip are from a time period when southern Africa was covered by ice,” he said.
“People obviously knew that part of the world had been covered in ice at one time, but no one had ever mentioned anything about how the drumlins formed or that they were even there at all.”
Andrew’s teamed up with colleague Andy McGrady to see if the drumlins showed any patterns that would show how the ice carved them.
They saw that the drumlins featured large grooves, indicating the ice had to be moving relatively quickly. These grooves are the first evidence of an ice stream in southern Africa in the late Palaeozoic Age, about 300 million years ago.
“The ice carved big, long grooves in the rock as it moved,” said Andrews. “It wasn’t just that there was ice there, but there was an ice stream. It was an area where the ice was really moving fast.”
McGrady said the scientists’ paper about the discovery, published in the journal PLOS One, was pioneering because it was one of the first attempts to describe the grooves and how they were formed.
The scientists also claim their evidence of the glacial activity supports the belief that the South American and African continents were connected at the time they were encased in ice.
They say the northwestward flow of ice from an ice cap in southern Africa — which was over the South Pole at the time — “likely discharged into the shallow marine environment several hundred kilometres downstream in modern Brazil”.
Twyfelfontein is famous for at least 2,500 rock carvings attributed to shamanistic hunter-gatherers and was approved by Unesco as Namibia’s first world heritage site in 2007.