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Effects of the Last Glacial Maximum in the northern Prince Charles Mountains
A vast ice-covered moraine field.
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Recent mapping of lateral moraines located alongside the major glaciers in the northern Prince Charles Mountains has been aimed at identifying those associated with the Last Glacial Maximum (LGM), ~20,000 years ago. The altitude of these moraines, relative to present glacier surfaces, provides an indication of how large the glaciers were at that time. Contrary to previously held beliefs that substantial glacier expansion, up to hundreds of metres, occurred during the Last Glacial Maximum, these lateral moraines are located only tens of metres above the present glacier surfaces, indicating that there were, in fact, only modest increases in ice volume. This work, which includes an on-going cosmogenic isotope exposure age dating study of boulders from the lateral moraines, has important ramifications for understanding the way in which the Antarctic Ice Sheet and outlet glaciers respond to climate change.
The photo, right, is a view towards the east across a vast ice-covered moraine field on the northern side of Crohn Massif, Porthos Range, northern Prince Charles Mountains. This is a type of lateral moraine feature, deposited by the Scylla Glacier. It consists of a thin (<1m) layer of boulders deposited over very slow moving or stagnant ice. The arcuate ridges next to the snowbank at the left are from a small rock glacier that is flowing into the moraine field from the slopes of Crohn Massif.
Moraine on the lower slopes of Martin Massif.
| Last Glacial Maximum (~20,000 years ago) moraine on the lower slopes of Martin Massif. The LGM is marked by the boulder scatter and abrupt line that runs across the slope on the right side of the image. The moraine is 40m above the area of scattered snowbanks and ice-covered moraine below.
Last Glacial Maximum lateral moraine ridge on the eastern slopes of Mount Creighton. The relatively unweathered angular boulders of the moraine (on the right of the image) contrast with the much older subdued, weathered, and boulder-free surface (to the left).
The photo, below left, shows an aerial view of the lower slopes of eastern Loewe Massif, northern Prince Charles Mountains. The curving line running from the bottom left is a moraine ridge deposited by the Nemesis/Charybdis Glaciers during the Last Glacial Maximum. Ice flowed from right to left. The area is about 3 km from and 150m above the present glacier. Note the contrast between the dark brown, very bouldery surface of the Last Glacial Maximum moraine area, and the subdued, red-brown boulder-free surface to the upper left. This suggests a considerable age difference between the two land surfaces.
Aerial view of the lower slopes of eastern Loewe Massif.
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View of the Last Glacial Maximum moraine ridge shown in the previous image.
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The photo, above right, shows a view of the Last Glacial Maximum moraine ridge shown in the image, above left. Eastern slopes of Loewe Massif, northern Prince Charles Mountains in the background. Ice flowed from left to right depositing the dark brown bouldery ridge behind the quad. Boulders are mainly charnockite derived from Loewe Massif.
Aerial view, below left, towards the southwest across the southern part of Radok Lake, Amery Oasis, northern Prince Charles Mountains. The Battye Glacier ice tongue floats on the lake surface which is located 7m above sea level. The ice on the lake is ~2 m thick, and is semi-permanent. Areas around the edge and near the ice tongue melt each summer, and occasionally the whole surface becomes ice free. Radok Lake is the deepest lake in Antarctica. A sounding by Jon Luly and Mark Mabin in 1996 near the tip of the ice tongue reached 335m depth. Previously, Russian scientists had reported a depth of 346m but it is not known where this was taken. The floating part of the Battye Glacier ice tongue is about 2 km long and flows at about 80 m per year. Since this image was taken in January 1990, several hundred metres of the tip have broken off and floated away to the north.
Aerial view towards the southwest across the southern part of Radok Lake, Amery Oasis.
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Slopes at the northern end of the Radok Lake basin.
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Slopes at the northern end of the Radok Lake basin, above right. These slopes are cut in the sandstones of the Amery Group rocks and rise about 150m above the lake. The horizontal line running across the slope about two-thirds of the way up is believed to be a lake shoreline formed when Radok Lake was considerably deeper than at present, but it is not known when this occurred.
Information Sources:
Mabin, M.C.G. (1992) Late Quaternary ice surface fluctuations of the Lambert Glacier. In: Yoshida, Y., Kaminuma, K. and Shiraishi, K. (editors) Recent Progress in Antarctic Earth Science, p. 683-687. Terra Scientific Publishing Company, Tokyo.
Mabin, M.C.G. (personal communication, 1997)
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