MARINE ice-pushed mounds and ridgesFootnote * formed by sea ice, growlers and bergs are common on the Arctic beaches. Crescentic ice-pushed ridges are found on both modern and elevated beaches at Slidre Fiord, Ellesmere Island, N. W. T. The material in the ridges is derived from the scars which are associated with them. The slope which faces the scar is flat, due in part to the fact that it may have been overridden by the ice, whereas the other slope of the ridge is steep. The ridges are a few feet in height and several feet long. One ridge was found which is more than 20 ft. (6 m.) above sea level and many scores of feet from the strand line. It may have been formed when the sea level was higher, or during the present sea level by ice thrust above and beyond the highest tide line. Ice-pushed ridges and crescents were not seen on the elevated beaches at Resolute Bay,Cornwallis Island, N. W. T., but are common on the modern beach. They are as much as 2 ft.high, but are not usually permanent, as the waves destroy them soon after they are formed Fig. 1, (p.173).
Fig.1 Ice-pushed ridges and the floes which formed them. Allen Bay, Cornwallis Island, N. W. T. 22 August, 1949.
Shingle heaps up to 60 ft. in height at Hillock Point, Melville Island, N. W. T., have been reported by M’Clintock.Reference M’Clintock 1 Armstrong described mounds on the north-west coast of Banks Island, N. W. T., which he said were upwards of 100 ft. in height. He wrote concerning them, “The appalling evidence we were afforded of the effects of pressure, caused by stormy winds acting on a trackless icy sea, … we had not witnessed in any other part of our eventful voyage, and baffles all attempts at describing—mounds being piled together to the height of upwards of 100 feet.” Reference Armstrong 2 , Reference Washburn 3 The great height reported for these mounds, much greater than those published by later observers of these mounds and ridges, makes one wonder whether they are due to: (1) Ice-push. (2) Morainal material dropped from drifting bergs. (3) Preglacial or glacial topography. (4) Beach shingle which owes its height in part to elevation of the shoreline. (5) A combination of processes. A study of Armstrong’s and M’Clintock’s texts makes it seem unlikely that these heights were obtained by precise measurement.
Lacustrine ice-pushed ridges are usually small features a few feet or more in height. A more or less continuous lacustrine ridge 6 ft. (1.8 m.) high on the landward side and between 8 and 9 ft. on the lakeward side is located on a delta on the east side of the lake, west of the meteorological station at Resolute Bay, Cornwallis Island, N. W. T. Fig. 2, (p. 173). This must be a particularly favorable place for the formation of lacustrine ice-pushed ridges, for it is considerably higher than those which are usually described.Reference Buckley 4 , Reference Scott 5
Fig. 2 An ice-pushed ridge on the margin of a lake at Resolute Bay, Cornwallis Island N. W. T. Knapsacks in the background give the scale
An ice-pushed ridge is also located on the east side of the lake at the foot of the bedrock ridge to the east of the settlement. It is, in places, about 12 ft. wide and between 3 and 4 ft. high on its landward side. It is asymmetric in transverse cross-section; its landward side is nearly at the angle of repose, while its lakeward side is much flatter. The ridge is made of many pushed units and on its lakeward side a thin layer of silt, sand and pebbles had recently been added. This layer is also similarly asymmetric in transverse cross-section and its surface is grooved and striated. The grooves and striations were formed by round stones and fragments which were pushed across the surface of the silt layer by the ice. Fine material plowed forward by the round stones and fragments is piled up on their landward sides.
