Rushing Floodwaters from Melting Glaciers May Have Created a Cliff

Scientists may have uncovered new clues to melting glaciers. They've found the aftermath of rushing floodwaters from melting glaciers in an unusual landform in the Wabash River Valley in southern Illinois. The new findings may reveal how floodwaters might behave as glacier melt increases in places like Greenland.

Along the western edges of the Wabash River Valley lies a short cliff that's about 10 to 20 feet high and runs in nearly a straight line for about six miles. Called the Meadow Bank scarp, the cliff runs nearly perfectly parallel to a fault zone one mile to the west. The scientists believed it was possible this scarp was formed by some past seismic activity around the fault.

In order to better understand this activity, the scientists probed the relationship between the fault and the scarp. Surprisingly, though, they found no relationship at all.

Intrigued, the scientists then talked to miners and studied records from the White County Coal Company, which mined coal throughout the area around and under the Meadow Bank. They confirmed that there was no fault or seismic activity hidden under the bank.

So what was happening? The scientists bored into the ground and took samples along and around Meadow Bank. They found evidence that the scarp was actually formed by erosion and that this erosion was produced by a strong force, such as a flood surge from a melting glacier.

"Looking at the layers in the sediment, you can trace back to big floods at the end of the last glacial time," said Timothy Larson, one of the researchers, in a news release. "As the glaciers melt, the water may build up in lakes along the glacier edge until it gets so deep that it overflows and rushes out in a big discharge," said Timothy Larson, one of the researchers, in a news release. "We see this happening today in places like Iceland. So at some point, a glacier flushed a huge slug of water, full of sediment debris, through the Wabash River Valley. It may have happened several times. It washed everything out and formed this straight shot down through the valley."

The findings are published in the journal Seismological Research Letters.

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