Moderator: Moderators
http://en.wikipedia.org/wiki/DrumlinA drumlin is an elongated whale-shaped hill. Drumlins may be more than 150 ft (45 m) high and more than ½ miles (0.8 km) long, and are often in drumlin fields of similarly shaped, sized and oriented hills."
http://www.uwsp.edu/geo/faculty/ritter/ ... umlin.htmlA drumlin is a streamlined, elongate hill composed of glacial drift. Drumlins are often found in swarms; their tapered end pointing in the direction of glacier advance.
http://en.wikipedia.org/wiki/Ribbed_morainesA ribbed moraine (also called a Rogen moraine) is a type of moraine shaped like an elongated hill. Ribbed moraines occur in groups or "fields" oriented transverse to former ice flow and look similar to giant current ripples.
http://en.wikipedia.org/wiki/DrumlinThere are many theories as to the exact mode of origin and plenty of controversy among geologists interested in geomorphology. Some consider them a direct formation of the ice, while a theory proposed since the 1980s by John Shaw and others postulates creation by a catastrophic flooding release of highly pressurized water flowing underneath the glacial ice. Either way, they are thought to be a waveform (similar to ripples of sand at the bottom of a stream).
http://www.geography-site.co.uk/pages/p ... /drum.htmlThere is still some debate about how drumlins are formed, but the most widely accepted idea is that they were formed when the ice became overloaded with sediment. When the competence of the glacier was reduced, material was deposited, in the same way that a river overloaded with sediment deposits the excess material. The glacier may have experienced a reduction in its competence for several reasons, including melting of the ice and changes in velocity. If there is a small obstacle on the ground, this may act as a trigger point and till will build up around it.
http://en.wikipedia.org/wiki/Ribbed_morainesTheir exact origin is a matter of debate. The main theories are:
- differential erosion by catastrophic release of meltwater
- ductile deformation of unfrozen sediments
- brittle deformation of frozen sediments
They look like the ridges that form out of sand near the shore in the ocean..otseng wrote:Drumlins and ribbed moraines are typically believed to have been created by glaciers.
http://en.wikipedia.org/wiki/DrumlinThere are many theories as to the exact mode of origin and plenty of controversy among geologists interested in geomorphology. Some consider them a direct formation of the ice, while a theory proposed since the 1980s by John Shaw and others postulates creation by a catastrophic flooding release of highly pressurized water flowing underneath the glacial ice. Either way, they are thought to be a waveform (similar to ripples of sand at the bottom of a stream).
http://www.geography-site.co.uk/pages/p ... /drum.htmlThere is still some debate about how drumlins are formed, but the most widely accepted idea is that they were formed when the ice became overloaded with sediment. When the competence of the glacier was reduced, material was deposited, in the same way that a river overloaded with sediment deposits the excess material. The glacier may have experienced a reduction in its competence for several reasons, including melting of the ice and changes in velocity. If there is a small obstacle on the ground, this may act as a trigger point and till will build up around it.
http://en.wikipedia.org/wiki/Ribbed_morainesTheir exact origin is a matter of debate. The main theories are:
- differential erosion by catastrophic release of meltwater
- ductile deformation of unfrozen sediments
- brittle deformation of frozen sediments
Right, drumlins and ribbed moraines look like they are formed by water, not ice.goat wrote:They look like the ridges that form out of sand near the shore in the ocean.
Yes, by retreating glaciers. The sand and soil are left behind in heaps as the glacier melts.otseng wrote:Right, drumlins and ribbed moraines look like they are formed by water, not ice.goat wrote:They look like the ridges that form out of sand near the shore in the ocean.
Here is a picture of ripples formed by water:
There are only two ways that I know of that ripples can form in soil/sand - by water or wind.
How can ice form ripples of soil/sand?
How can retreating glaciers form mounds of dirt?goat wrote: Yes, by retreating glaciers. The sand and soil are left behind in heaps as the glacier melts.
otseng wrote:How can retreating glaciers form mounds of dirt?goat wrote: Yes, by retreating glaciers. The sand and soil are left behind in heaps as the glacier melts.
How can it form ripples?
Are there any retreating glaciers now that do this?
Why would it form drumlins that are parallel to the direction of the ice flow and perpendicular to the ice flow for ribbed moraines?
How can melting glaciers form drumlins between 5 and 50 meters high?
Long Island is not a drumlin nor a ribbed moraine nor a ripple.goat wrote:A melting glacier formed Long Island. THat seems to be a bit bigger than 50 meters high.
