Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/199

Rh AND CIRQUES IN NORWAY AND GREENLAND. 1(51

metres.

Height of boulders in Tronfjeld 1600

Height of the valley below 500

Thickness of the ice at Tronfjeld 1100

Height of boulder on Solen 1741

Height of the country below 700

Thickness of the ice at Solen 1041

Height of erratic boulders on Suletind 1770

Height of the lake of Utrovand below 986

Thickness of the ice at Suletind 784

Height of erratic boulders on Graagalten 756

Height of the lake of Soneren at the foot 118

Thickness of the glacier at Graagalten 638

Height of erratic boulders on Skriru 900

Height of the country below 250

Thickness of the glacier at Skrim 650

From the above we may draw the following picture of Norway in the Glacial Epoch. The fjords were filled up by glaciers, which attained a thickness of fromjlTOO to 1800 metres in the Sogne Fjord and 1200 metres in the Hardanger ; the lateral fjords debouching into these contained glaciers 800 metres thick, supplied from an inland ice-sheet at least from 800 to 1100 metres thick. The icy mass also extended over South-eastern Norway, where it was not less than 600 or 700 metres thick.

On the formation of Cirques and Valleys ending in Cirques. — In those parts of Norway and Greenland which abound in small isolated glaciers unconnected with any large ice-field, we find a great number of recesses called Cirques, in Norsk " Botner " (bottoms). These cirques are large spaces excavated from the solid rock, bounded on three sides by an almost semicylindrical steep mountain- wall, and with a tolerably flat floor. When the upper part of a valley terminates in a cul-de-sac, so that its gently sloping bed comes to an abrupt end against a steep mountain-wall, this too is called a " Botn " (cirque). The latter kind of cirques may for convenience be called " valley cirques," the former " mountain cirques," though there is no essential difference between them. I shall describe the mountain cirques first.

The dimensions of these cirques are variable, their length and breadth being often about the same and varying from some hun- dred to some thousand metres. If the length greatly exceeds the breadth, this passes into a " valley cirque." The mountain- walls around the cirques vary from 50 to 400 metres in height, sometimes being even as much as 700 metres ; and in Greenland, in the sound between Upernivik Island and the mainland, I have seen a cirque surrounded by an almost vertical wall, which rose nearly 1000 metres above the glacier which filled the cirque. The surface of