E
sker Formation
Eskers are formed during the time of maximum glacial extension when ice movement is slow and sluggish. Streams within (endoglacial) and beneath (subglacial) the glacier carve out ice tunnels (above) which slowly fill with sediment as the glacier retreats.
. The resultant sharpcrested esker is a narrow winding ridge characterized by steep sides (below left).
It is possible for eskers to form by debris filling up crevasses on the retreating glacier. These typically form flattened broadcrested eskers (above right) with shallower sides and wider tops.
Eskers usually don’t survive periods of reglaciation and thus the modern eskers we see today were formed in the last Ice Age 10-15000 years ago. They are typically 5 to 30 metres in height and can extend for many miles. The worlds longest esker, The Thelon Esker, runs for 497 miles between the Northwest Territories and Nunavut in Northern Canada.
Given their particulate composition, eskers make excellent aquifers and provide communities with clean water.
Logging requirements
- Using your GPS determine the height and width of the esker at GZ.
Note. No need to bushwhack down the slope, there is a sidetrail just down the trail from GZ.
- Given the definitions from the cache page what type of esker is this, broadcrested or sharpcrested ?
- Note the direction of the esker, in which direction (N,S,E or W) do think its glacier would have receded.
- Amongst the sand and gravel you will notice some stones originally ground from the bedrock by the glacier and carried to Brampton before being deposted in the esker. Do you think the rock is hard round dolostone or thinly layered shale ?
Email me your answers via my profile page. No need to wait for feedback, go ahead and log the find. I will contact you if there are any issues. An optional photo of you and/or your GPS near GZ is always appreciated.
Congratulations to Fred F. for his fast, frantic FTF in the middle of a thunderstorm !!!!