Raymond Effect is a flow effect in
ice sheets
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
, occurring at
flow divides, which gives rise to disturbances in the stratigraphy, showing unusual arches or
anticline
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
s called ''Raymond Arches''.
The stratigraphy is detected by
radio-echo sounding. The Raymond effect arises from the unusual flow properties of
ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaqu ...
, as its viscosity decreases with
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
. It is of importance because it provides field evidence for the flow properties of ice.
In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness.
The effect was first predicted by Charles F. Raymond.
Raymond Arches and the Raymond Effect have been observed at numerous other ice divides e.g.
Siple Dome
Siple Dome () is an ice dome approximately 100 km wide and 100 km long, located 130 km east of Siple Coast in Antarctica. Charles Bentley and Robert Thomas established a "strain rosette" on this feature to determine ice movement in ...
,
,
Berkner Island
Berkner Island (also known as the Berkner Ice Rise or as Hubley Island) is an Antarctic ice rise, where bedrock below sea level has caused the surrounding ice sheet to create a dome. If the ice cap were removed, the island would be underwater. Be ...
,
,
[ Korff Ice Rise.]viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
is stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
-dependent, and in zones where the (deviatoric) stresses are low, the viscosity becomes very high. Near the base of ice-sheets, stress is proportional to the surface slope, at least when averaged over a suitable horizontal distance. At the flow divide, the surface slope is zero, and calculations show that the viscosity increases.
References
Glaciology
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