Donnerstag, 1. Januar 2009

Beyond the Mountains of Madness

Digital Elevation Model of the bedrock of the Antarctic continent. The ice weigth pinch the bedrock up to 1.000m under the current sea level, only an "archipelago of islands" is still reaching up from the sea.

Antarctica apparently is composed of only two major, geologically distinct parts bridged by a vast ice sheet. Rock exposures comprise only 1-3% of the land area, and are limited to isolated coastal regions and to alpine elevations in the Transantarctic Mountains.

East Antarctica, the larger of the two is composed of at least Precambrian dated igneous and metamorphic rocks, covered by an ice sheet that can reach 4.000m thickness. West Antarctica, the smaller portion, is a mosaic of small blocks (minimum five) of continental crust covered by the West Antarctic Ice Sheet and shows as most prominent feature the mountain chain forming the Antarctic Peninsula. The Antarctic Peninsula was formed by uplift and metamorphism of sea-bed sediments during the late Paleozoic and the early Mesozoic, subduction is probably still occuring on the coast region of the peninsula.

The two blocks are separated be the Transantarctic Mountains, a 2.800km long mountain chain, with peaks that reach 4.000m. This mountains follows the Transantarctic Rift-systems – the true limits of the two landmasses.

Even if the crust of East Antarctica is thought to represents a stable continental shield, still geophysical investigations showed prominent mountain ranges buried under ice, like the Gamburtsew-subglacial-mountains, a 1000km long mountain range, up to 3.000m high.

It is not clear how this mountains came to being – hypothesis range from volcanic origin to a very old subduction mountain chain (implying that east Antarctica is not a homogenous crust block) or a gondwanian relict of compress- tectonics (also implying that the geological history is much more complicated then previously though).

Maybe future drill-programs and geological investigations can solve the riddle of these real Mountains of Madness.

PIOMBINO, A. (2008): I monti Gamburtsev: una grande catena montuosa totalmente sepolta sotto i ghiacci antartici la cui origine è ancora sconosciuta.

LYTHE, M.B., VAUGHAN, D.G. and the BEDMAP Consortium. 2000. : A new ice thickness and subglacial topographic model of the Antarctic.

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