Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island

Abstract

The geomorphology of Heard Island± McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745 m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava ¯ows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene± Early Pliocene Drygalski Formation, which forms a 300 m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, sur® cial sediments, and contemporary geomorphological processes, including glacio¯uvial sediment ¯ux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.

Föhn winds on South Georgia and their impact on regional climate

“…Glaciers at Kerguelen in the Southern Indian Ocean (Frenot et al, 1993; and in southern Patagonia have shown to be shrinking and retreating at accelerated rates (Aniya et al, 1997;Aniya, 1999;Rignot et al, 2003;Rivera & Casassa, 2004). Likewise, rapid glacier recession over the last decades, reflecting temperature rise since the 1950s and 1960s has been found in several locations, including Heard Island (Allison & Keage, 1986;Kiernan & McConnell, 1999;Budd, 2000), and the South Shetland Islands (Braun et al, 2001;Simões et al, 2004).…”

Sediment movement rates and processes on cinder cones in the maritime Subantarctic (Marion Island)

“…Hall, 1983a,b;Heilbronn and Walton, 1984a;Löffler et al, 1983;Löffler, 1984;Holness and Boelhouwers, 1998;Kiernan and McConnell, 1999;Holness, 2001a). However, as few process observations and almost no experimental data are available, much of the interpretation of the processes active in the region remains speculative.…”

Polar Coasts

“…Small sand beaches can be found in other protected north-facing sites (Hall and Denton, 2000), but are rare on the mainland. More extensive sand beaches are present on the sub-Antarctic islands, where the subaerial and glacial environment delivers large volumes of sand and gravel to the coasts of South Georgia (Figure 16(c) and 16 (d)) (Gordon and Hansom, 1986), Heard Island (Kiernan and McConnell, 1999), and the nearby Îles Kerguelen (Hansom and Gordon, 1998). Unlike the Arctic coast, where glacial tills and moraine are found in association with extensive deposits of fluviatile sands and gravels, a very different situation occurs on the Antarctic continent.…”