review the key theories behind surge-type behaviour in glaciers and their significance in explaining the present-day distribution of Earth’s surging glaciers;
Introduction
Surge glaciers are a poorly understood glacier type, different literatures describe them as different thing and many differ on their formation, causes and even what can be classified as a surge glacier. One definition is “a glacier that switches between phases of rapid and slow flows on a timescale ranging between a few years to several decades” however the same source also describes what a glacial surge is defining it as “a cyclic phenomenon which are not directly triggered by external events, but instead result from internally driven oscillations in conditions at the bed …show more content…
(Sugden and John, 1979). Although cycles of surging can vary from years to decades the surge event period can last varying timescales anywhere from few months to several years(knight, 1999)
Causes of Surge Glaciers
There are many theories in what causes surges, some revolve around glacier hydrology based around the idea of low water velocity but high water storage. (Knight, 1999). There are currently 3 main theories behind the mechanisms that cause surge glaciers; these are thermal, hydrological and the deformable bed mechanisms. However there are also other theories there are also less well studied reasons as to what causes surge glaciers or in fact surges themselves.
Thermal …show more content…
The Hydrological method is based around the idea that water propagates to the base of a glacier, this allows water levels to build up. If this occurs during winter it can cause water to be trapped in sub glacial pipes at the base of the glacier and can cause subtle bulging, and uplift of the glacier (Craig and Dennis, 2003). It appears so far that this is possibly due to collapsing of water channels within the glacier effectively “jacking” it up from the base (Paterson and cuffey, 2010). Once jacked up and after the winter period if the glacier has enough water stored to maintain surge motion whilst also be thick enough (thus having enough weight) to allow the surge to begin it will start sliding (Craig and Dennis, 2003).
Deformable bed
Introduction
Surge glaciers are a poorly understood glacier type, different literatures describe them as different thing and many differ on their formation, causes and even what can be classified as a surge glacier. One definition is “a glacier that switches between phases of rapid and slow flows on a timescale ranging between a few years to several decades” however the same source also describes what a glacial surge is defining it as “a cyclic phenomenon which are not directly triggered by external events, but instead result from internally driven oscillations in conditions at the bed …show more content…
(Sugden and John, 1979). Although cycles of surging can vary from years to decades the surge event period can last varying timescales anywhere from few months to several years(knight, 1999)
Causes of Surge Glaciers
There are many theories in what causes surges, some revolve around glacier hydrology based around the idea of low water velocity but high water storage. (Knight, 1999). There are currently 3 main theories behind the mechanisms that cause surge glaciers; these are thermal, hydrological and the deformable bed mechanisms. However there are also other theories there are also less well studied reasons as to what causes surge glaciers or in fact surges themselves.
Thermal …show more content…
The Hydrological method is based around the idea that water propagates to the base of a glacier, this allows water levels to build up. If this occurs during winter it can cause water to be trapped in sub glacial pipes at the base of the glacier and can cause subtle bulging, and uplift of the glacier (Craig and Dennis, 2003). It appears so far that this is possibly due to collapsing of water channels within the glacier effectively “jacking” it up from the base (Paterson and cuffey, 2010). Once jacked up and after the winter period if the glacier has enough water stored to maintain surge motion whilst also be thick enough (thus having enough weight) to allow the surge to begin it will start sliding (Craig and Dennis, 2003).
Deformable bed