A meltwater channel, or sometimes a glacial meltwater channel, is a channel that has been meticulously carved. It can be found etched into ice, bedrock, or even the more yielding unconsolidated deposits. Its origin? The relentless flow of water, undeniably derived from the slow, inevitable melting of a glacier or a vast ice-sheet. [1] These channels are not confined to a single location relative to the ice mass; they can manifest on its surface, burrow within its frozen depths, lie hidden beneath its immense weight, trace its edges, or extend downstream from its retreating form. Consequently, these are described with specific terminology: supraglacial if on the surface, englacial if within, subglacial if beneath, lateral (or ice-marginal) if alongside, and proglacial if downstream.
Within the specialized lexicon of glaciology, several distinct forms of subglacial channel have been identified and meticulously described. Among these are the Nye or N-channels, the Röthlisberger or R-channels, and the Hooke or H-channels. [2] The term tunnel valley serves as a related descriptor, particularly adept at characterizing these subglacial channels. In certain regions, such as northwest England, some of these tunnel valleys have even been referred to with the evocative term iceways. [3] Furthermore, it's worth noting that depositional landforms like kames and eskers, themselves products of glacial activity, are frequently observed in close proximity to meltwater channels, suggesting a shared geological history.
A particularly notable type of channel, often found in Germany and Poland, is the urstromtal. These are extensive proglacial or ice-marginal channels that were formed during various phases of the Pleistocene glaciations, periods when the colossal Scandinavian ice sheet exerted its influence over the landscape. The term spillway is also occasionally employed to denote a channel carved by water that has overflowed from a body of water, such as a proglacial lake. Compelling examples of major glacial lake outbursts creating significant spillways are well-documented, particularly along the southern boundaries of the Laurentide icesheet in North America. [4]
The phenomenon of meltwater channels is not exclusive to Earth. Evidence of meltwater channels associated with glaciation has been compellingly identified on the surface of Mars itself. [5] This discovery offers fascinating insights into the planet's past hydrological and climatic conditions.
See also
- Fluvioglacial landform – Landforms created by the action of meltwater from glaciers.