3. Glacial erosion, transport and deposition Flashcards
Where are erosion rates high and low?
High close to ice sheet margins
Low at ice divides
What is the basic sequence of glacial processes?
erosion → transport → deposition
What creates abrasion (scratching)?
basal debris, not ice itself
What are the three forms of glaciotectonism?
Bulldozing: materials are pushed to the front
Squeezing: Ductile process, materials are pushed to the front and then squeezed and folded
Thrusting: Brittle deformation
What is true for the PMP, Pressure Melting Point?
Everything below is warm, everything above is cold
What is glacier ”plumbing” about?
Englacial water drains in a ”karstic” system, following cracks and conduits (under increasing pressure) towards glacier bed. There, it joins the subglacial drainage system.
Although some supraglacial water reaches glacier snout, much enters the englacial system via crevasses and moulins (sinkholes)
What is striae?
elongated scratches made by abrasion, parallel to the ice movement direction
Simple, nailhead, rat-tail (ridge behind obstacle)
Name other small erosional forms
- Striae
- Crescentic marks
- Grooves
- Channels
- Potholes
Name larger erosional forms
- Roches moutonneés
- Crag-and-tails (smth big with a tail)
- Drumlins, MSGLs, flutings (not necessarily erosional)
- Glaciated valleys (U-shaped, bottom and flank erosion)
- Tunnel valleys (go up and down in topography unlike rivers, start and end seemingly nowhere)
What is transported supraglacially?
Supra = on top
material from avalanches, wind-blown, up-sheared, volcanic, cosmic (meteorites)
What is transported basally?
Basal = at the base
material mostly eroded from local substratum, abraded (rounded, faceted, scratched, bullet-shaped)
What is transported englacially?
Englacial = in the middle of the ice
material up-lifted from the ice bed or lowered from the ice surface
What is transported subglacially?
Subglacial = underneath the ice
soft, water-saturated, weak, unconsolidated material mobilized by ice movement (deforming bed)
