In Ontario, there are larger Drumlin fields with hundreds of well-defined drumlins, in particular the Peterborough Drumlin field which contains over 2000 individual drumlins, and is the largest field in central Canada. These large fields are important for study as they allow geologists to follow the flow of the advancing glacier.
While the study of Drumlins and their creation has been ongoing for over 150 years, scientists are now able to use new technology, in particular Satellite laser imagery or LiDAR, a surveying method that measures distance to a target by illuminating that target with a laser light. One question that has stumped scientists is whether the drumlins were built up progressively or sculpted out of older sediment. University of Toronto Professor Nick Eyles and his team including both PhD and undergraduate students have been studying these streamlined “islands” of sediment at locations where the Drumlin layers are exposed, for example where a hill has been bisected for a roadway. Their research recently published in the journal Sedimentary Geology supports the theory that drumlins and mega-ridges are part of a single family of landforms that were formed by erosion.
Using LiDAR technology, scientists are able to study the underlying surface of the drumlin even when covered by trees and water, to expose the layered surface changes in the sediment. Scientists are also looking at modern examples of retreating glaciers in Greenland and Antarctica where slow moving ice sheets can contain faster flowing corridors called ice streams that are moving as fast as 1km annually.
These streams are moving large volumes of ice to the margin of the ice sheet. As the ice streams thin and retreat as the earth warms, they are exposing the underlying beds which include these mega-ridges, where the ice appears to flow faster across the bed by creating a slippery, low friction surface. As the debris is dragged over the surface of the ridge, it acts like sandpaper and is highly erosive, sculpting and progressively whittling down the mega ridge into a smooth, long, tapered hill.
Logging requirements
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1. At the posted coordinates you will be able to see the exposed, eroded end of a drumlin hill located in Rouge Hill. Ridge Road runs along the axis of the drumlin hill if you want to take a short drive. Based on your understanding of the formation of this Drumlin, what direction was the glacier flowing when the drumlin was created?
2. Based on your knowledge of the shape of a drumlin, do you believe this drumlin hill has eroded significantly since the last ice age, and if so, what is the most likely reason?
3. Based on your observations is the erosion likely to continue or have measures been put in place to prevent future erosion? List all of the factors that may contribute to future erosion based on your observations at this location.
4. Looking at the cross section of the exposed drumlin, can you see evidence to support Dr. Eyles theory that layers of sediment built up over time? Are there differences in the colour of sediment or deposits of large boulders, or cobbles that form a defined layer?
5. Are the layers horizontal or do they show evidence of the formation of the hill? For example are the layers semi-circular or curved?
6. Optional: Photo’s are appreciated however no spoiler pictures please.
References:
ONTARIO ROCKS three billion years of environmental change - Nick Eyles
http://phys.org/news/2016-03-unravelling-geological-mystery-lasers-space.html#jCp
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