Drumlins are elongated hills, with streamlined shape. They occur in groups with similar orientation. The name "drumlin" is Irish, and there are thousands of them in that country. In 1865 the drumlins of Ireland were attributed to glacial movement by H.M. Close. Since then, almost all writers on the subject of drumlins have assumed they are of glacial origin, although no mechanism for drumlin formation by ice action has been discovered. When considered as the effects of currents of the deluge, drumlins can be quite easily explained. Their distribution patterns provide information about the way in which the flood waters retreated from the land.
This aerial (courtesy of Dr William Bowen, California Geographical Survey Northridge, California) shows the Eureka Drumlin field in the USA and the Tobacco Plains Drumlins in Canada
A glacier flowed southward through this valley during the last ice age, advancing as far as Polson (about 90 miles from Eureka). As the ice pushed through the area it pulverized bedrock and sediments, forming a mixture of boulders, cobbles, sand, sand and clay called “till” or Boulder Clay. This unsorted mixture of rock materials is what the drumlins are made of. Glaciers transport and eventually deposit till in shapes called moraines, kames, and eskers. In fact the town of Polson sits atop a moraine that helped Flathead Lake to form. Although geologists have a reasonably good understanding of how glaciers build moraines, kames, and eskers, the processes that form drumlins remains somewhat mysterious. It is also poorly understood why drumlins form in some glaciated areas and not in others.
Cross Sections of a Drumlin.
The following is an excerpt from Dr Bowen, who also indicates that:The word drumlin comes from the Irish Gaelic word druim, which means "ridge". Perhaps the most famous drumlin is Bunker Hill in Massachusetts.
A Bottleneck to blame? . . . One theory about the formation of the Eureka Drumlins is that the glacier slowed or stagnated upon reaching a narrow portion of the valley 10-15 miles south of Eureka. During warmer periods within the ice age, melting from the bottom and/or front of the glacier may have deposited a significant amount of till in the area. Then, during colder periods the glacier would have started to advance once again, causing thicker ice to flow over the deposits. Pressure from the weight of this somewhat thicker ice may have shaped the rock material into the distinct tadpole-shaped drumlins. Since the till was not deposited and shaped simultaneously, this theory suggests that the Eureka drumlins are “erosional” landforms.
The posted coordinates are where cachers would park to observe this Drumlin. This parking spot is beside the entry to Grasmere Road. Please observe the rule of leave no traces.
To log this earthcache, please email the owner with the following: a) number of people in your group b) approximate direction this Drumlin is pointing c) Approximate height of the head at this location d) how far down the road and which direction is the tail (e) your opinion whether the glaciers deposited or was it erosional
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