Lecture 5 Flashcards
(25 cards)
What glaciological processes govern glacial landform formation and distribution?
Whether the bed is frozen, thawed rock or
thawed sediment
How does flow occur in the case of a frozen bed?
If the bed is frozen, the flow occurs as internal deformation of the ice, meaning that no landforms are created at the bed: It preserves the pre-existing landforms and creates proglacial/ice-marginal meltwater landforms
Why is glacial geomorphology important?
- tell about land forming and processes through the quarternary period
- provides data for establishing the extent, dynamics, and timing of paleo ice sheets, ice caps, and alpine glaciers
- reconstruction of paleo glaciers and ice sheets is an important component in validating numerical glaciers and climate models
What are the main glacial landform processes?
Glaciofluvial landforms
Glacial depositional landforms (constructional)
Glacial erosional landforms (destructional)
What glaciological conditions govern glacial landform distribution and formation?
Function of ice temperature and pressure (Basal-thermal and pressure melting point)
What determines whether ice slides or is frozen to its bed?
The basal-thermal distribution (ice temperature)
What is the pressure melting point of a glacier?
The temperature at which ice melts at a given pressure
How does flow occur in the case of thawed rock bed?
Flow occurs as basal sliding/deformation, meaning that landforms are created at the bed and in front of ice, producing subglacial and ice-marginal landforms
How does flow occur in the case of thawed sediment bed?
Flow occurs as basal sliding/deformation which creates landforms and subglacial deformation. It preserves landforms in the core area and produces landforms in thawed regions
5 Glacial ersosional landforms
Fjords
U-valleys
Cirques
Roches mountonnees
Striae
4 Glacial depositional landforms
Drumlins
Fluting
Ribbed moraines
End moraines
Glaciofluvial landforms
Eskers
Marginal meltwater channels
What does the meltwater pathways variation depend on?
Temperature distribution in the ice.
What is abrasion?
A glacial erosional process that wears down or rubbs away by means of friction. Subglacial sediment or individual rock fragments slides over the bedrock.
What is the glacial erosional landform Striae?
Strekkmerker.Glacial stritations or striae are scraches cut into the bedrock by glacial abrasion
What is the glacial erosional process called plucking?
Plucking is the fracturing of bedrock beneath a glacier and the entrainment of the fractured or crushed bedrock. It requires basal sliding, well-jointed bed rock lithology, and cavities.
What is the glacial erosional landform Roche moutonnee?
In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. Abrasion on the upstream side of the rock and plucking on the downstream side.
How does the glacial landform Cirque form?
It forms when snow accumulates in small cracks and hollows in a mountain. Gravity pulls the glacier downhill. The hollow becomes deeper through plucking and abrasion.
How does the glacial landform U-valley form?
A u-valley a glacial erosional process and is formed when a glacier travels across and down a slope, carving the valley by abrasion. When the ice recedes or thaws, the valley remains.
How does the glacial landform Fjords form?
A fjord is formed by glacial erosion when a glacier retreats after carving its typical U-shaped valley, and the sea fills the resulting valley floor.
How do end moraines form?
End moraine forms at the end of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion is deposited in an unsorted pile of sediment. The longer the glacier stays in one place, the greater the amount of material that will be deposited.
What are glacial flutes?
Glacial flutes are low, narrow, elongated, straight, parallel ridges that range between several centimeters to a few meters in width and height, consisting of glacial till, sand, silt, and clay. They form subglacially and are orientated parallel to the direction of glacier flow.
What are ribbed moraines?
Ribbed moraines are glacial depositional landforms. They are most likely formed by the fracturing of frozen pre-existing till sheets at the transition from cold to warm-based conditions under deglaciating ice sheets.
What are marginal meltwater channels?
Marginal meltwater channels are glaciofluvial landforms formed when meltwater discharge allows erosion. They are formed along former ice margins.
