Land and Water, Glaciated Landscapes Flashcards
What can be inferred by New Zealand’s abundance of valleys?
That, unlike Australia, it was a highly glaciated landscape
Glacier
A large mass of perenial ice resting on land or adjacent to it. Moves downslope due to their weight and gravity
Firn
Compacted snow
How is the accumulation zone of glaciers linked to their movement?
The accumulation zone is the build up of snow/ice at the source. As this ice/snow thickens, its mass increases, causing flow to occur
What are the two types of flow?
- Basal slip
- Plastic flow
Basil slip
The melting of ice/snow on the ground due the combined effect of temperature and pressure. Water reduces friction, allowing it to slide
Plastic
The internal deformation of ice
Ablation zone
The melting zone of snow/ice at the downstream margin. This zone melts faster than the accumulation zone, making the glacier appear to move upwards
When was the last glacial maximum?
18,000 years ago during the Pleistocene when ice sheets and glaciers covered 30% (now 11%) of Earth’s land area
Where do glaciers form?
In places of high latitude and/or altitude
What are the two theories of glacier formation?
- Plate tetctonics
- Milankovitch cycles
Plate tectonics of glacier formation
In the continent of Pangea 300 million years ago, there were higher latitude location. The moving land mass would have changed ocean currents, subsequently changing climate
Milankovitch cycles of glacier formation
Periodic variations in Earth’s orbit which reduced the intensity of solar radiation, allowing glaciers to form/expand
What two erosional processes are carried out by glaciers?
- Abrasion
- Plucking
Abrasion
Glaciers scraping against the surrounding environment
Plucking
Glaciers picking up and freezing eroded sediment
What two landforms are charcateristic of past glacial environments?
- Smooth surfaces (glacial polish once glacier retreats)
- Striations from abraded material chiseling the surrounding environment
What type of sediment is produced by glaciers?
Glacial flour: Very fine grained sediment that is constantly worked upon by fluvial and aeolian processes
What type of valleys are prduced by fluvial and glacial processes?
Fluvial: V-shaped valleys
Glacial: U-shaped valleys
What is the gernal term for glacial deposits and its two subtype?
General term: Drift
- Till
- Straified drift
Till
Unsorted and unstratified sediment deposited directly from melting ice
Stratified drift
Sorted and bedded deposits from fluvial processes or other weathering or erosional processes
What are the three types of moraines?
- Lateral (start/edges)
- Medial (middle/meeting point)
- Terminal (end/foot)
What are the three main post-glacial features?
- Drumlins
- Outwash plains
- Loess deposits
Drumlins
Oval, elongated hills shaped by the streamlined movement of glaciers
Outwash plains
Flat, expansive areas dominated by braided rivers due to the active melting of glaciers
Loess deposits
Fine-grained sediment that is blown vast distances to prduce fertile plains
What climate is needed for periglacial geomorphology?
Cold climates that allow glaciers to form temporarily, causing the the ground to permafrost
What is the active layer of periglacial environments?
The zone of seasonally frozen ground between the subsurface and permafrost layer. This layer experiences constant freeze-thaw cycles
What are the two freeze processes?
- Frost heave
- Freeze-thaw
Frost heave
The vertical and horizontal movement of particles that are in the process of freezing
Freeze-thaw
The repititive melting and freezing of ice. The expansion of water due to freezing causes rocks to fracture. Produces very distinctive patterns on the ground
Eustacy
The rise and fall of sea level due to changes in water quantity. Also occurs due to changes in the shape and capacity of basins
Isostasy
The rise or fall in land due to changes in elevation of the Earth’s crust. This changes relative sea level
Glacio-isostasy
The regional/local rise or fall of land caused by the melting or expansion of ice sheets. This can cover new coastlines or reveal older, drowned coastlines
