Flashcards in G - Glacial Landforms Deck (24):
How do glaciers create basins?
-Snow collects in hollows (usually in the side with the most accumulation ad least ablation)
-Snow collects in hollows and turns into ice. Basal sliding with abrasion and plucking deepen the hole into a corrie
(When the ice in the hollow is thick enough, it flows over the lip and downhill as a glacier - frost shattering an plucking steepen the back wall of the corrie
Name as many glacial erosion landforms as you can (10 in total)
- Pyramidal peak
- Glacial trough
- Hanging valley
- Truncated spurs
- Valley steps
- Ribbon Lakes
- Roche mountenée
What is an arête?
A steep sided ridge
How is an arête formed?
Formed when two glaciers flow in parallel valleys. The glaciers erode the sides of the valley, which sharpens the mountain ridge on between them
What is a pyramidal peak?
A pointed mountain peak with at least three sides
How is a pyramidal peak formed?
Where three or more corries from back to back (their back walls make the mountain peak)
What is a glacial trough?
(Also called a U-shaped valley) - steep sided valleys with flat bottoms
How is a glacial trough formed?
By the erosion of a V-shaped river valleys by glaciers, as the glacier erodes through the v-shaped it makes them deeper and wider
What is a hanging valley?
Valleys formed by tributary glaciers
How is a hanging valley formed?
When tributary glaciers erode the valley floor much less deeply because they're smaller than the main glacier - so when the glaciers melt, the valleys get left at a higher level than the glacial trough formed by the main glacier
→ You get waterfalls from hanging valleys into the main glacial trough
How are truncated spurs formed?
When ridges of land (spurs) that stick out into the main valley are chopped off (truncated) as the main valley glacier moves past
What are valley steps?
Steps in the glacial trough
How are valley steps formed?
When the glacier erodes the valley floor more deeply - this happens when another glacier joins it or where there's less resistant (softer) rock
What are tarns?
Lakes that form in corries after a glacier has retreated
What are ribbon lakes?
Long, thin lakes that form after a glacier retreats
Where do ribbon lakes form?
In dips caused by erosion of bands of less resistant rocks, or behind dams of debris left by the glacier
What are Fjords and how do they form?
Long, deep inlets that form when a valley that's been eroded by a glacier is flooded by sea level rise after the ice has melted
What is a roche mountenée?
A resistant (hard) mass of rock on the valley floor
Explain how a roche mountenée forms and why?
The upstream (stoss) side is smooth, due to abrasion as the glacier went over it. The downstream (lee) side is steep and rough where the glacier plucked at it
What is moraine?
Formations of till deposited by a glacier as it melts
What are the types of moraine? Explain them (formation)
Lateral moraine - deposited where the sides of the glacier were
Medial moraine - Formed from the two lateral moraines of two glaciers merge
Terminal/end moraine - marks the furthest point that the glacier reached, often a high mound/series of mounds of debris that extend across a valley
Recessional moraine - often parallel to terminal moraine - mark the retreat of a glaciers retreat - each recessional moraine reflects a stage when glacial retreat was halted long enough for deposition to concentrate in 1 area
Subglacial - beneath the glacier
Englacial - inside the glacier
Supraglacial - debris accumulated on top of the ice
What are drumlins? Name and explain its features an give an example of a group
Smooth, asymmetrical, elongated mounds of till
The upstream side is the stoss side which is wide and tall
The downstream side is the lee side which is narrow and low
There are a group of Drumlins in the Ribble Valley, Lanchashire
What are the measurements for till?
Up to 1500m long and 100m high