Lake Greenhow: A Forgotten Relic of the Ice Age

Yesterday’s post led me to glaciers, glacial lakes, and the like. At Botton Head, my imagination ran riot.

Difficult as it is to picture now, 10,000 years ago, a glacier covered the Tees Valley before me. The ice sheet, it is well-known, never quite managed to smother the North York Moors. So, naturally, I wondered if it extended down the whole of the valley of Greenhow Botton like a backwater in the flow of a river.

Frank Elgee—archaeologist, geologist, naturalist, and general authority on such things—believed a small proglacial lake was once at the head of the valley. He theorised that an overflow spilled across the southern watershed into Bilsdale, though I would argue Bransdale makes more sense¹Elgee, Frank. Nature Notes. | Northern Weekly Gazette | 28 November 1903.

According to Elgee, at Botton Head the ground takes an abrupt and inexplicable dip before just as suddenly rising again. This conveniently placed depression, now home to the old Rosedale mineral railway, is said to be the overflow channel of the supposed lake. When the water level reached the lowest point in the hills, it spilled over into the next dale, carving itself a channel in the process. Eventually, the ice retreated, the drainage returned to its old ways, and the channel dried up, leaving yet another monument to the Ice Age²Elgee, Frank. GEOLOGICAL NOTES. | Northern Weekly Gazette | 27 September 1902.

I note that this overflow channel sits at just over 400 metres above sea level—considerably higher than those of other known glacial lakes such as Scugdale (310 metres) and Eskdale (a mere 160 metres). If Lake Greenhow did exist, it must have been a rather deep one.

So, where did the glacier end and the lake begin? The British Geological Society records glacial till—clay, sand, and gravel—deposits over much of the valley, including Old Shepherd Farm, but conveniently not at Shepherds Close Farm. This suggests, to my mind, that the edge of the cultivated fields marks the glacial face rather neatly. Meanwhile, How Hill—the distinctive 166-metre knoll topped with trees, from which Greenhow takes its name—is said to be a small glacial mound³Proceedings of Cleveland Naturalists’ Field Club 1905-06. Page 3. Available online at http://barlow.me.uk/clevelandnats/1905_6. A minor relic of a rather significant past.

• 1
  Elgee, Frank. Nature Notes. | Northern Weekly Gazette | 28 November 1903
• 2
  Elgee, Frank. GEOLOGICAL NOTES. | Northern Weekly Gazette | 27 September 1902
• 3
  Proceedings of Cleveland Naturalists’ Field Club 1905-06. Page 3. Available online at http://barlow.me.uk/clevelandnats/1905_6