. British Antarctic expedition, 1907-9, under the command of Shackleton : reports on the scientific investigations ; geology. ormed in the first case at a depth of about 100 fathoms. This beach too, like that of Backstairs Passage, is, partly at any rate, underlaid 2 M 270 SUPERFICIAL DEPOSITS by glacier ice. There can be no doubt that the ice underlying the Cape Barne raised beach is a relic of the Great Ice Barrier. Fig. 63 below shows the theoretical structure of the Drygalski-Larsen-ReevesPiedmont ice, the section being taken from south-east to north-west, nearly at rightangles to the
. British Antarctic expedition, 1907-9, under the command of Shackleton : reports on the scientific investigations ; geology. ormed in the first case at a depth of about 100 fathoms. This beach too, like that of Backstairs Passage, is, partly at any rate, underlaid 2 M 270 SUPERFICIAL DEPOSITS by glacier ice. There can be no doubt that the ice underlying the Cape Barne raised beach is a relic of the Great Ice Barrier. Fig. 63 below shows the theoretical structure of the Drygalski-Larsen-ReevesPiedmont ice, the section being taken from south-east to north-west, nearly at rightangles to the rib of the Larsen Glacier. The thrust has come chiefly from thedirection of the great Drygalski Glacier rib, which has transmitted its thrust,not of course through the two open channels to its left (these are shear planes),but through areas nearer the shore-line, where the shear plane walls are firmly incontact with one another. Part of Reeves Il Piedmont ice Vpthrust marine mudsZOPabmeseacmereflwith large angularblodiS of granite a^Quartz porphyry\resting on ice Larsen Piedmontm/fl neevy moraine Drygalski Piedmont. Longitudinal ScaleVertical Scale. tsooD (600O Metres4000 feet~ Soo Metres Fig. 63. Uptkrust Marine Muds and Raised Beaches The following alternative explanation to the upthrust hypothesis may besuggested;— The region near Backstaiis Passage is one where there is a large amount ofmoraine material either upon the ice or embedded in it. As already explained,absorption of the suns heat by blocks of rock leads to then- being so warmed up thatthey rapidly melt their way into the ice beneath and become englacial. Thus theglacier ice in the neighboui-hood of moraines becomes heavily loaded with blocks ofrock, and so its mean density may be so much increased that it exceeds that of seawater and becomes what may be termed rock-loaded, or rock-logged. A sub-mergence of the land taking place later sea-level relatively rose, and the glacierice, weighted down by its r
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