It is named after its main feature, a long, water-filled depression parallel to the river.

Two hundred and eighty million years ago, during the Permian period, dolomite (magnesium limestone) formed here.

The original quarry can still be seen opposite the River Don, adjacent to the Sprotbrough Flash lake.

[7] The long lake from which the name of the reserve is derived is the result of subsidence caused by the collapse of old coal mines.

[9] The fauna includes common kingfishers, brown hare, grass snakes, Eurasian bitterns, ruddy darters, and the great crested grebe.