How do glacial landforms evolve over time as climate changes? Flashcards
What are glacio-fluvial landforms?
Landforms produced by meltwater from glaciers.
They include both erosional and depositional features.
What happens to glacio-fluvial landforms during periods of glacier readvance?
They are often severely modified or degraded.
This occurs as glaciers advance again.
What is outwash and how does it differ from till?
Outwash is sediment deposited by meltwater and is generally smaller, smoother, sorted, and stratified.
In contrast, till is unsorted and deposited directly by glacial ice.
What are kames?
Hills or hummocks composed of stratified sand and gravel laid down by glacial meltwater.
They can form through various processes including the collapse of debris-filled crevasses.
What is an esker?
A long, sinuous ridge composed of stratified sand and gravel laid down by glacial meltwater.
Eskers are formed in sub-glacial tunnels as meltwater decreases.
Define outwash plain.
A flat expanse of sediment in the pro-glacial area formed by the deposition of meltwater streams.
They are typically drained by braided streams.
Why can glacial meltwater be produced at different times?
Due to seasonal melting and deglaciation events.
This variability affects the formation of glacio-fluvial landforms.
What are the conditions of periglacial environments?
Permafrost, seasonal temperature variations, and freeze-thaw cycles.
These environments occur in high latitudes and continental interiors.
What is the significance of freeze-thaw cycles in periglacial environments?
They dominate geomorphic processes such as frost heave.
This leads to the formation of unique landforms.
Describe the relationship between particle size and settling velocity.
Larger particles settle faster than smaller ones.
This relationship is important for understanding sediment deposition.
How do kame terraces form?
From supraglacial streams depositing material on the valley floor as the glacier retreats.
They are composed of glacio-fluvial deposits unlike moraines.
What is the role of hydrostatic pressure in esker formation?
It may influence deposition when meltwater pressure is released at the glacier snout.
This can explain the beaded appearance of some eskers.
What defines periglacial environments?
Areas with permafrost, seasonal temperature variations, and freeze-thaw cycles
Permafrost is perennially frozen ground overlain by an active layer
Where are periglacial environments typically found?
High latitude areas, continental interiors, and high mountains
Examples include Alaska, Siberia, Plateau of Tibet, Andes, and Alps
What percentage of the Earth’s land surface is made up of periglacial environments?
25 percent
Another 25 percent has experienced periglacial conditions in the past
What is the dominant weathering process in periglacial environments?
Freeze-thaw weathering
This is due to seasonal fluctuations in temperature around freezing
What is frost heave?
A sub-surface process that leads to vertical sorting of material in the active layer
Stones heat up and cool down faster than their surroundings, leading to upward movement
How does the development of ground ice occur?
Water percolates into sub-surface geology, freezes, and expands during winter months
This pushes the ground surface upwards
What is patterned ground?
A collective term for small-scale features in periglacial environments
Formed by frost heave and movement of stones
What are pingos?
Rounded ice-cored hills that can be up to 90 m in height
They grow at rates of a couple of cm/year
What is the main difference between open-system and closed-system pingos?
Open-system pingos form in valley bottoms; closed-system pingos develop beneath lake beds
Open systems involve water from surrounding slopes; closed systems are isolated
What happens to pingos when temperatures rise?
They collapse, leaving a rampart surrounding a depression called an ognip
Relict ognips can be found in regions like Britain
How does human activity affect periglacial landscape systems?
Through extraction of resources and construction, impacting material and energy flows
This includes oil extraction and road building
