Tuesday, June 21, 2011

Mount McKinley (Denali)

Mount McKinley or Denali (Koyukon Athabaskan for "The High One", Dghelaayce’e in Ahtna) in Alaska, United States is the highest mountain peak in North America and the United States, with a summit elevation of 20,320 feet (6,194 m) above sea level. The CIA World Factbook lists its summit elevation as 6,198 metres (20,335 ft). It is the centerpiece of Denali National Park and Preserve.

Geology and features

Mount McKinley is a granitic pluton. It has been uplifted by tectonic pressure while at the same time, erosion has stripped away the (somewhat softer) sedimentary rock above and around the mountain.

The forces that lifted Mount McKinley—the subduction of the Pacific plate beneath the North American plate—also raised great ranges across southern Alaska. As that huge sheet of ocean-floor rock plunges downward into the mantle, it shoves and crumples the continent into soaring mountains which include some of the most active volcanoes on the continent. Mount McKinley in particular is uplifted relative to the rocks around it because it is at the intersection of major active strike-slip faults (faults that move rocks laterally across the Earth's surface) which allow the deep buried rocks to be unroofed more rapidly compared to those around them.


Layout of the mountain

Mount McKinley has two significant summits: the South Summit is the higher one, while the North Summit has an elevation of 19,470 feet (5,934 m) and a prominence of approximately 1,320 feet (402 m). The North Summit is sometimes counted as a separate peak (see e.g., the List of United States fourteeners) and sometimes not; it is rarely climbed, except by those doing routes on the north side of the massif.

Five large glaciers flow off the slopes of the mountain. The Peters Glacier lies on the northwest side of the massif, while the Muldrow Glacier falls from its northeast slopes. Just to the east of the Muldrow, and abutting the eastern side of the massif, is the Traleika Glacier. The Ruth Glacier lies to the southeast of the mountain, and the Kahiltna Glacier leads up to the southwest side of the mountain.

Notable features

Mount McKinley has a larger bulk and rise than Mount Everest, although the summit of Everest is higher at 29,029 feet (8,848 m). Everest's base sits on the Tibetan Plateau at about 17,000 feet (5,200 m), giving it a real vertical rise of little more than 12,000 feet (3,700 m). The base of Mount McKinley is roughly at 2,000-foot (610 m) elevation, giving it an actual rise of 18,000 feet (5,500 m). The mountain is also characterized by extremely cold weather. Temperatures as low as −75.5 °F (−59.7 °C) and windchills as low as −118.1 °F (−83.4 °C) have been recorded by an automated weather station located at 18,700 feet (5,700 m). According to the National Park Service, in 1932 the Liek-Lindley expedition recovered a self-recording minimum thermometer left near Browne's Tower, at about 15,000 feet (4,600 m), on Mount McKinley by the Stuck-Karstens party in 1913. The spirit thermometer was calibrated down to 95 °F below zero and the lowest recorded temperature was below that point. Harry J. Liek took the thermometer back to Washington, D.C. where it was tested by the United States Weather Bureau and found to be accurate. The lowest temperature that it had recorded was found to be approximately −100 °F (−73 °C).

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