This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, March 18, 2012

A most unusual river meander: The River Wear at Durham, England

File:Durham 1610.jpg
I have seen river meanders in a number of different settings--along the relatively flat stretches of rivers in the Midwest of the U.S., in bedrock along the Colorado River in Arizona, and, most impressively, in the famous Goosenecks of the San Juan River. These meanders were clearly formed at an earlier time and, we often presume from theories of river meandering, on nearly flat, erodible ground. They are also meanders that I've only seen by river rafting and hiking through the desert terrain of the Southwest.

Tonight I sit in acomfortable apartment at Durham University (England), wrapped in a river meander that has played a role in history. The river in view from my apartment window flows in a stately manner that we would call "subcritical" in the hydraulics terminology.  Rowing teams are practicing on the flat water for competition, which culminates for northern England on the second weekend in June with the championships. The enclosed ground, far from the isolated desert peninsulas in such settings in the Southwest, comprises the city of Durham, a World Heritage site for its culture and geography. It is a very different perspective to be sitting in a comfortable apartment high on the bluffs on the peninsula enclosed by the meander than to be camping on a beach at the base of such bluffs!

The meander looks, at first, like a classic incised meander--formed earlier in time on flatter land, and then incised into underlying bedrock as the land was lifted through tectonic processes. But, unlike the meanders in the American southwest, this meander has survided glaciation. How did that happen? We think of glaciers as giant bulldozers that flatten, or at least, subdue, the high ground that they traverse--the American Midwest. The ground of the peninsula enclosed by the meander is anything but flat--so steep and hilly that in the few days that we've been here, we've only seen one bicyclist (leaning hard on her brakes as she went downhill). Everyone walks instead of cycles! How did all this topography survive the glaciation? It is strikingly different from our glaciated Midwest.

Glaciation in this area reached its peak about 18,500 years ago. The glaciers receded starting about then, but paused right here where I am sitting as a guest of Durham University about 14,000 years ago.  I can see that I might like to stay in this fantastic place for 500 years, but why would a glacier pause here for that long? The answer will, hopefully, be in a future post!

Readers might enjoy this geographer-at-large blog!


Sue said...

Thanks, John!

Anonymous said...

I am intregued by two things you have written in your blog re. Durham incised meander
1. How do you know it was formed before the LGM (last glacial maximum) - are there references for this?

2. Where did you find the information re. the last glacial in durham. how do you know it paused in Durham?