Periglacial and Glaciofluvial key terms Flashcards
what is a post-glacial period?
When a glacial period ends because of a rise in temperature.
- Followed by an inter-glacial period.
What is a kame and what are the two types?
A hill composed of outwash
- Delta Kame (centre of valley) or a Kame Terrace (along edge of valley floor)
what do glacio-fluvial streams deposit?
- Outwash
- Smooth and rounded because of attrition
What is a Jökulhlaup?
A glacial flood caused by sudden melting of ice.
What is an esker?
A long sinuous ridge of stratified sand and gravel formed by glacio-fluvial streams during post-glacial periods.
Glaciofluvial landform
What is deltaic deposits?
When a glacio-fluvial stream enters a lake and outwash forms a ridge of deposit.
(delta = river enters lake or ocean)
Eskers are beaded. What does beaded mean?
That the pattern of the land is not continuous and it changes depending on the speed of glacial retreat.
What is an outwash plain?
A flat expanse of land with lots of deposit in a proglacial area
What is a pro-glacial area?
Beyond glacial ice.
What is a kettle hole?
Formed in a post glacial environment as a glaciofluvial landform.
- Ice in a hole melts = hole.
(kettle = warm water into cup with ice = melt)
What is a braided stream?
- Meltwater streams in an outwash plain.
- Braided because they are divided due to deposit build up.
- A glaciofluvial landform
What’s a Periglacial environment?
- Non-glacial area
- Cold, permafrost
- freeze thaw cycles because of distinct seasonal variations.
What is frost heave?
- A process occurring in periglacial environments
- Water below stones freezes then expands which forces stones towards the surface.
- Upwards movement
- Creates a domed surface = patterned ground
What is patterned ground?
- Periglacial landform
- Frost heave forces stones to surface = domes
- Stone polygons on the permafrost
- stones distinctive around the domes because of slopes.
What is ground ice?
Water percolates into talik and geology.
Increases (underground) water table in summer months due to melting.
- Freeze in colder months = expand by 9-10% = ground surface is raised due to expansion (= pingos).
What is solifluction?
Thawing of material (talik) causing it to move down a hill in periglacial environments eg. soil.
- Form solifluction lobes.
What is a solifluction lobe?
- Periglacial environment (due to seasonal variations)
- Solifluction: movement of thawed material in warmer months downhill
- Saturated soil moves, but moisture does not percolate or infiltrate because of permafrost
- Re-freeze in colder months.
- forms icing style line 〰️
What is talik?
Unfrozen ground in a periglacial environment.
What is a pingo?
- Dome formed by ground ice (infiltrated water in summer and frozen in winter = expand = uplift)
- Open or closed.
What is an open pingo?
- Artisan pressure forces groundwater aquifer to surface which builds up below permafrost.
- Freeze and expands in colder seasons
= dome
What is a closed pingo?
- Saturated soil/ talik freezes in colder seasons.
- talik expands
- Pushes permafrost up
What is the active layer?
The section of permafrost that thaws during the annual seasonal fluctuations.
What is regolith?
-Regolith is stones that are within the active layer.
- Creates layers during summer months due to rock density = vertically sorted.
What is a pro-glacial lake?
- A glacio-fluvial landform
- Glacier blocks natural drainage
- Melting of glacier post-glacially
- Overflow forming a lake.
-eg Lake Aggasiz in southern Minnesota beyond the ice.
What is a glacio-fluvial landform?
A landform that exists as a result of climate change (post-glacially) with outwash
