Page:Canadian Alpine Journal I, 2.djvu/127

Rh of gravel, sand and clay, differing strikingly from the moraines formed previously and subsequently. Between the great blocks, many of enormous size, spaces permit the entrance of man and other animals, so that Professor Tarr's name of "bear-den moraine" seems appropriate. Space will not permit a detailed discription [sic] here of these moraines, nor a full discussion of their probable origin. There is no reason for thinking that the ordinary filling material was originally present and removed by running water, or other agency. The blocks were not pushed along ahead of the ice, nor carried subglacially, but were carried either upon or within the ice. The ordinary proces of weathering would produce as much fine as coarse material and give rise to a terminal moraine of the ordinary type. An inspection of the cliffs from which the blocks were apparently derived shows that in all the five cases the general trend is northwest to southeast and that the bulk of the material was dropped to the eastward. The only plausible explanation which the writer has been able to frame is that these glaciers became loaded with these coarse blocks as the result of a double earthquake disturbance, which probably crossed the Rockies and Selkirks in a northeast-southwest direction. The two shocks were separated by two or three centuries and the first was either the most severe, or else it found more loose material awaiting its arrival. The mountains of the region appear to have served as a gigantic seismograph to record the time, number, relative intensity and direction of the shocks. A very rough estimate based upon the rings of growth of trees, indicates that these disturbances happened from 700 to 1000 years ago, or from the loth to the 13th centuries. Glaciers like the Geikie, whose bounding cliffs extend in a northeast-southwest direction, i.e., in the direction of wave transmission, would be able to secure but a slight load and might reasonably be expected to show no such