EQ3: Formation of glacial landforms and landscapes? Flashcards
What is glacial erosion?
The removal of rock material by ice through abrasion, plucking and meltwater flow from ice margins
Glacial erosion is a key process in shaping landscapes affected by glaciers.
Define glacial debris entrainment.
Sediment being incorporated into glacial ice and carried along with the ice
This process is crucial for understanding how glaciers transport sediment.
What is glacial sediment transport?
Sediment being moved on top of (supraglacial), within (englacial) or at the base (subglacial) of ice
Different transport mechanisms can affect the characteristics of the sediment.
What occurs during glacial deposition?
Material is dropped from the ice at the margin or the base of a glacier and deposited, or deposited from meltwater
Glacial deposition results in the formation of various landforms.
What are macro-scale glacial landforms?
Cirque/ corries, aretes, pyramidal peaks, glacial troughs, ribbon lakes, till plains, moraines, knock ‘n lochans
These landforms provide evidence of former glacial conditions: its extent, size, etc.
List meso-scale glacial landforms.
- Roches moutonnees
- Drumlins
- Kames
- Eskers
- Kettle holes
Meso-scale landforms are intermediate in size and also indicate glacial activity.
What are micro-scale glacial features?
- Striations
- Chattermarks
- Erratics
Micro-scale features provide fine details about glacial movement and processes.
Describe proglacial areas.
Occur in front of ice masses where meltwater deposition and wind action on glacially eroded sediments took place
Proglacial environments are significant for sediment transport and landform development.
What defines periglacial areas?
Areas that had no ice cover but were underlain by permafrost
Periglacial regions are important for studying climate conditions and their effects on landscapes.
What is the process called when a glacier detaches large particles of rock from the bedrock?
Plucking
What is quarrying in the context of glacial erosion?
An extreme form of plucking, creating steep and angular rock cliff faces.
What happens during abrasion in glacial erosion?
Sharp rock fragments embed in the ice and grind down the bedrock, leaving scratches called striations.
What is freeze-thaw weathering?
Weathering that occurs on rock slopes above valley glaciers, providing angular rock fragments.
What is a corrie?
An armchair-shaped, steep-sided hollow at the head of a glaciated valley.
What direction do corries often face in the northern hemisphere?
North or North East facing
What initial process deepens the hollow of a corrie?
Nivation~
~ erosion of the ground around a slope of snow due to freezing and thawing
What can accumulate behind the lip of a corrie in a post-glacial period?
Water, forming a tarn.
What is an arête?
A narrow ridge formed when several corries lie close to one another and erode back into the mountain.
How are pyramidal peaks formed?
By glaciers eroding a mountain from three or more sides, resulting in a sharp peak.
What are glacial troughs?
U-shaped valleys that develop where glaciers flow into pre-existing V-shaped river valleys.
What features characterize the formation of glacial troughs?
They are steep-sided with a wide, flat base and often include truncated spurs.
What is a ribbon lake?
A lake formed in a rock basin created by uneven glacial erosion, often filling post-glaciation.
What causes the formation of hanging valleys?
When ice in a tributary valley cannot erode effectively due to blockage by ice in the main valley.
Fill in the blank: Glacial troughs develop where glaciers flow into pre-existing _______ river valleys.
V-shaped
True or False: Hanging valleys are always larger than the main glacial trough.
False
What is a truncated spur?
Cliffs left behind when glaciers straighten the valley and cut off spurs.
What are rouches moutonnees?
Isolated rocks, generally between 5 to 30m in height, along the base of a glaciated valley
Characteristically smooth on one side and jagged on another, formed by glacial movement over harder rock.
How do rouches moutonnees form?
They form where a glacier moves over a band of harder rock, smoothing the upstream side by abrasion and leaving striations
The downstream side is jagged due to plucking of loose rocks.
What are knock ‘n’ lochan?
Scottish names for an irregular landscape of small ice-sculpted hills (knocks) and small lakes (lochans)
Result from widespread abrasion and plucking by an ice sheet.
What type of rock primarily forms knocks in the Scottish landscape?
Hard metamorphic rock
This rock type is sculpted by glacial activity.
What is a crag in the context of glacial landforms?
A resistant rock that forms an outstanding feature, less eroded than surrounding rock
Represents part of the differential geology in glacial landform creation.
What is created in the lee of a crag?
The tail, formed by deposition of eroded material
This feature is characteristic of crag and tail landforms.
What is an example of a crag and tail feature?
Edinburgh Castle and the Royal Mile down its tail
Exemplifies how crags can serve as prominent landmarks.
Fill in the blank: Rouches moutonnees are smooth on one side and _______ on another.
jagged
This contrast is a key characteristic of rouches moutonnees.
True or False: Crag and tails are formed by the erosion of the same type of rock.
False
They form through differential erosion, where resistant rock remains while surrounding rock erodes.
What are moraines?
Unconsolidated and unsorted angular materials created by glacial depositional processes.
Moraines can take various forms based on their location relative to the glacier.
What are end moraines?
Terminal and recessional moraines.
Terminal moraine marks the maximum position of the ice, while recessional moraines mark the stand-still position of a glacier during melting.
What does a terminal moraine indicate?
The maximum position of the ice.
Terminal moraines are usually arc-shaped and can be tens of meters high and kilometers long.
What is a lateral moraine?
Material located along the edge of valley glaciers where the ice meets the valley wall.
Debris is constantly dropped onto the ice due to weathering and mass movement.
What is produced when two valley glaciers meet?
A medial moraine.
The respective lateral moraines merge into a medial moraine running down the middle of the larger glacier.
What is a drumlin?
An oval-shaped hill often formed of moraine deposited as a glacier moves forwards.
Drumlins indicate the direction that the glacier was flowing in.
List the characteristics of a drumlin.
- Oval-shaped hill
- Up to 50 m tall
- 200-1,000 m long
- Steeper ‘stoss’ end pointing up-ice
- Gently sloping ‘lee’ end pointing down-ice
- Can be rock-moulded or made of glacial sediments
- Often found in groups
The landscape can be described as ‘a basket of eggs’ topography.
What is till?
Unconsolidated sediment deposited by a glacier, consisting of a mix of clay, boulders, and gravel.
Lodgement till is deposited under the ice, while ablation till is deposited by melting ice.
What do terminal moraines indicate about glacial history?
The extreme edge of a glacial advance.
They provide evidence for the maximum extent of ice.
How do drumlins provide evidence of glacial movement?
By their orientation and angle of long axis.
Erratics also provide evidence of the direction of movement.
What role does glacial meltwater play in glaciated landscapes?
It can erode channel networks and is involved in various fluvioglacial processes.
Meltwater can be subglacial, englacial, or supraglacial.
What is the difference between glacial and fluvioglacial deposits?
- Glacial deposits are unstratified; fluvioglacial are stratified
- Glacial deposits are poorly sorted; fluvioglacial are well-sorted
- Glacial deposits have random long-axis alignment; fluvioglacial have dominant directions
- Glacial deposits show little sign of grading; fluvioglacial are well-graded
These differences are significant in understanding glacial processes.
What are eskers?
Long, thin ridges made of sand and gravel left behind by subglacial, englacial, or supraglacial river channels.
They can be up to 100 m in height and extend for many kilometers.
What are kames?
Irregular mounds of sands and gravels produced at the edges of a glacier or ice sheet.
Kames often occur in groups and resemble cones or deltas.
What are sandhur?
Large areas of sandy and pebbly material washed out of the ice by meltwater streams.
They show layered deposits with larger deposits occurring each spring.
What are kettle holes?
Small, often circular, lakes formed by the melting of ice blocks left by a retreating glacier.
They can be observed in various regions, such as north Cheshire.
