Glacial Features

[kingwinner]

1) "The thin and tapered side (less steep) of the drumlin points in the direction of glacier movement"
But is it pointing to the direction of glacial advance or glaical retreat? The quote confuses me because a glacier moves both ways, i.e. advance and retreat, they move in opposite directions)
For example, in the diagram below, the thin and tapered side (less steep) of the drumlin is pointing to the bottom right, would this be pointing in the direction of glacial advance or glacial retreat?




2) Is a drumlin created when a glacier advance or when a galcier retreat?



3) "A col is a ridge separating 2 hanging valleys. It stretches from one horn to another"
Can someone explain? Is col indeed a ridge, not a valley?


4) "An interlobate moraine form between lobes of the ice sheet"
Between lobes? What actually does a glacier lobe mean?

[coldcreation]

Originally Posted by kingwinner

1) "The thin and tapered side (less steep) of the drumlin points in the direction of glacier movement"
But is it pointing to the direction of glacial advance or glaical retreat? The quote confuses me because a glacier moves both ways, i.e. advance and retreat, they move in opposite directions)
?

It is my impression that glaciers do not retreat in the sense implied. To retreat they would have to climb up hill. Glaciers all move downhill. Glaciers melt and chunks break off near the bottom, usually during summer months, or at the end of iceages. The glaciers that used to cover large portions of Europe, Asia, and North America melted away, they did not move back up north. So they do not "move both ways."

Hope that helps...

[Turtle]

Originally Posted by kingwinner

2) Is a drumlin created when a glacier advance or when a galcier retreat?



3) "A col is a ridge separating 2 hanging valleys. It stretches from one horn to another"
Can someone explain? Is col indeed a ridge, not a valley?


4) "An interlobate moraine form between lobes of the ice sheet"
Between lobes? What actually does a glacier lobe mean?

2) Drumlins emerge as the glacier retreats; glaciers retreat by melting at their leading edge & working the leading edge back uphill. The drumlins form from rock, gravel sand, etc. that drops out from the active melt zone at the leading edge & under the influence of gravity.
3) A hanging valley is one formed by a glacier lobe feeding a larger central glacier. When the glaciers melt back, a U-shaped bottom valley high up a wall of a larger valley is the resulting "hanging Valley". I read the reference as you state it, i.e. if two hanging valleys lay side-by-side, the ridge separating them is called a "col"
4) A glacier lobe is a separated arm of a larger glacier that is divided from other arms by an ice-free zone.


PS This Wikpedia article says in one place the cause of drumlins is unknown, & in another that they form under the active glacier as a wave effect. Interesting. The formation of moraines seems universally accorded to the dropping of material from the leading edge as I ascribed to the drumlins. Keep us posted Kingwinner.
http://en.wikipedia.org/wiki/Drumlin

[Greg]

well it looks like they are made when they reatreat...(perhaps so because og G Warming.)