While exploring Namibia, the desert country in southern Africa, a team of geologists from West Virginia University stumbled upon a peculiar land formation — flat desert scattered with hundreds of long, steep hills. They quickly realized the bumpy landscape was shaped by drumlins, a type of hill often found in places once covered in glaciers.
Namibia’s drumlins were formed by fast-moving ice floes instead of slow melting ice. Image credit: West Virginia University.
“We quickly realized what we were looking at because we both grew up in areas of the world that had been under glaciers,” said Dr. Graham Andrews, a researcher in the Department of Geology and Geography at West Virginia University.
“It’s not like anything we see in West Virginia where we’re used to flat areas and then gorges and steep-sided valleys down into hollows.”
“The last rocks we were shown on the trip are from a time period when southern Africa was covered by ice. 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,” he added.
To determine if the drumlins showed any patterns that would reflect regular behaviors as the ice carved them, Dr. Andrews and colleagues used morphometrics, or measurements of shapes.
“While normal glaciers have sequential patterns of growing and melting, they do not move much,” he said.
“However, we determined that the drumlins featured large grooves, which showed that the ice had to be moving at a fast pace to carve the grooves.”
These grooves demonstrated the first evidence of an ice stream in southern Africa in the late Paleozoic Era , which occurred about 300 million years ago.
“The ice carved big, long grooves in the rock as it moved. 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,” Dr. Andrews said.
The findings also confirm that southern Africa was located over the South Pole during this period.
“These features provide yet another tie between southern Africa and south America to show they were once joined,” he said.
The research appears in the journal PLoS ONE.
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G.D. Andrews et al. 2019. First description of subglacial megalineations from the late Paleozoic ice age in southern Africa. PLoS ONE 14 (1): e0210673; doi: 10.1371/journal.pone.0210673
