Landforms Flashcards
Describe the process of formation of till plains (lowland despoliation all features).
When ice retreats, large amounts of material are deposited over a sizeable area due to melting. Till plains occur when a large ice sheet becomes detached from a glacier and melts.
Describe the process of formation of lodgement till (lowland despoliation all features).
Lodgement occurs beneath the ice when debris that was being transported gets lodged or pressed into the glacier bed. It is associated with slow-moving glaciers that are carrying a lot of debris.
Describe the process of formation of ablation till (lowland despoliation all features).
Ablation is the melting of the ice and ablation till is deposited as the glacier melts. While lodgement till is made of sub-glacial material (carried under the ice), ablation till includes supraglacial and englacial material.
What method/diagram can be used to do till fabric analysis?
A rose diagram can be used to plot the orientation of the clasts.
What can erratics tell us about reconstructing past glaciation?
These are boulders dumped by glacial erosion in an area with a different rock type. Their own rock type can tell us where they were transported from (provenance) and analysing the distribution of erratics provides data about patterns of ice flow.
What can moraines tell us about reconstructing past glaciation?
Terminal moraines show the furthest extent of the glacier snout. The up-valley side of a terminal moraine often has a steeper slope than the down-valley side (pushed steeper by the snout), demarcating the glacial area from the pro-glacial.
What can drumlins tell us about reconstructing past glaciation?
The stops end points up-glacier, the lee end is down-glacier. The elongation index of drumlins indicates speed of ice movement - the more elongated, the faster the ice was moving.
What can till tell us about reconstructing past glaciation?
Till analysis of class orientation can indicate the direction of ice movement (clasts orientate to point in the direction of ice movement). Analysis of till geology can also help indicate provenance.
What can drag and tail tell us about reconstructing past glaciation?
The stows end points up-glacier, the lee end points down-glacier.
What can roches moutonnées tell us about reconstructing past glaciation?
Abrasion at the up-glacier end, plucking (jagged rock) at the down-glacier end.
What can striations tell us about reconstructing past glaciation?
These scratches made by glacial abrasion form parallel to the direction of ice movement.
