Surge (glacier)

A Surge (English [ sɜ ː dʒ ] literally for " wave ", " wave ") is a typically intermittent significant increase in the flow rate of a glacier. Glacier, where it occurs are called surge glaciers (also galloping glaciers ). In such glaciers to long periods solve with normal, slow flow velocity from shorter phases in which the glacier flows from 10 to 1000 times faster. The resting phase ( Quiescent phase ) may take decades or centuries, the active phase (surge phase ) typically takes from one to fifteen years. During a Surge considerable amounts of ice are shifted from the accumulation area in the lower portions of the glacier, the glacier terminus can also significantly advance, but need not. Of surge glaciers there are regional clusters, especially in Alaska and northwestern Canada, Iceland, Spitsbergen and in the Pamirs. The global average Surges occur at less than one percent of the glaciers. A very striking feature of surge glaciers is the occurrence of folded medial moraines that form when the main arm or Tributärgletscher have a different system glacier surge behavior.

The fastest precisely measured speed during a Surge in 1963 found the Brúarjökull in Iceland with 125 meters per day. It is often referred to as the "fastest glaciers in the world " the Kutiah glacier in the Karakoram, said to have covered approximately 12 kilometers during a surge from March to June of 1953, 113 meters per day as the average speed here specified. The most spectacular indication comes from Yengutz - Har Glacier, also in the Karakoram, is said to have traveled 3.2 km in eight days during its beginning in 1902 Surge.

Geographical distribution

Worldwide one percent of the glaciers are classified as surge glaciers, however, are due to the advances in remote sensing almost added every year to Glacier. Surges occur in a wide range of glacier types and sizes. Be overlooked, however, is that the geographic distribution is not uniform, accumulations occur on both a global and regional level. In many areas there is no surge glaciers, particularly large contrast in Alaska, the Yukon Territory, the central Andes, the Tian Shan, Pamir, Kamchatka, the Karakorum, Iceland, Spitsbergen, in the Canadian and Russian high Arctic and the the edge of the Greenland ice sheet. The disastrous forays of Vernagtferner in the Ötztal Alps, between the late 16th and the early 20th century are usually classified as a surge behavior, but today there is no such in the Alps more glaciers.

Possible Causes

Meanwhile regarded as certain that there must be more than one cause for this phenomenon. Two distinctly different types of surge glaciers have been identified: the Alaska - type ( Alaskan -type ) with a very abrupt transition between resting and active phase and the Svalbard - type ( Svalbard -type ) with more continuous transitions, longer phase duration and significantly lower flow rates. When Alaska type is tempered glacier and it is assumed that the phase transition is caused by a sudden change of the subglacial drainage system in conjunction with the debris deposits located at the glacier base. When Spitsbergen type a thermal cause is assumed that leads to the destabilization of the rubble interspersed glacier bed polythermalen a glacier. As a prototype of the Alaska - type applies the Variegated Glacier, the equivalent of the Svalbard - type is the Monacobreen.