Surge (glacier)

Glacial surges are short-lived events where a glacier can move up to velocities 100 times faster than normal, and advance substantially. Surging glaciers are clustered around a few areas. High concentrations of surging glaciers can be found in Svalbard, Canadian Arctic islands, and Alaska. Glacial surges take place at regular, periodic intervals, with the period in-between two surges called the quiescent phase. During this period the velocities of the glacier are significantly lower, and the glaciers retreat substantially.

Theory

Critical mass

There have been many theories of why glacial surges occur. One accepted theory, proposed by Meier & Post in 1969, suggests when the accumulation of mass reaches a critical level on the upper glacier - above normal amounts of water stored within the glacier trigger a surge. It does this by increasing the buoyancy for basal sliding.

Deformable bed hypothesis

It has also been suggested that the geology of the country rock, which the glaciers are on, might play some part in surges. The rock type can affect balance and velocity of glacial ice. It is thought that surging glaciers are most likely to be situated on sedimentary country rock. This explains why surging glaciers tend to cluster in certain areas.

References

• http://users.aber.ac.uk/kak3/glacier_surges.htm
• http://www.bgrg.org/pages/education/alevel/coldenvirons/Lesson%208.htm