G3 Landforms/ Landscapes Flashcards
(19 cards)
What are the main processes that create glacial landforms?
Erosion and deposition by ice and water
These processes shape the landscape over varying temporal and spatial scales.
What is subglacial erosion?
Erosion occurring at the base of a glacier, including processes like quarrying and abrasion
It involves the removal of bedrock and the grinding down of surfaces by rock particles.
Define quarrying in the context of subglacial erosion.
Removal of blocks (>100mm) from bedrock due to stress distribution and presence of melt water
This process can be accelerated by freeze-thaw cycles and hydro-fracturing.
What is abrasion in glacial processes?
The scratching of bedrock surfaces by rock particles at the base of a glacier
It creates striations and other rock-scoured features.
List the main controls on glacial abrasion.
- Basal contact pressure
- Rate of basal sliding
- Concentration and supply of rock fragments
These factors influence the effectiveness of abrasion on bedrock.
What characterizes subglacial meltwater erosion?
Processes similar to surface rivers, with mechanical and chemical erosion occurring
It plays a major indirect role in erosion by removing basal sediment.
What are the two types of glacial transport?
- High-level (passive) glacial transport
- Low-level (active) glacial transport
The type of transport is dictated by the sediment source and the glacier’s dynamics.
What is a medial moraine?
Ridges of debris formed in the middle of a glacier when two lateral moraines merge
They represent high-level transport of supraglacial debris.
What are the characteristics of high-level sediment in glacial transport?
- Retains primary characteristics
- Angular
- Coarse
- Little fine material
This sediment is typically transported at higher elevations on the glacier.
Describe low-level transport in glaciers.
Debris moved along the glacier bed
This process modifies the debris through crushing and rounding.
What is till in glacial sedimentation?
A glacial deposit made up of unsorted and unstratified material
It reflects the direct impact of glacial processes on sediment deposition.
Define lodgement till.
Sediment squeezed into bedrock under high pressure from overlying ice
It is often dense and can contain larger clasts embedded in finer material.
What is supraglacial melt-out till?
Material that slides down or slumps into margins or in front of the glacier as it melts
It often contains rounded particles deposited by meltwater.
What are ribbed moraines?
Ridges of basal till oriented perpendicular to ice flow
They have a shallow slope on the upstream face and a steeper downstream face.
What is a drumlin?
An elongated rounded hill, mostly composed of basal till, aligned parallel to ice flow
They are indicators of past ice flow dynamics.
How do drumlins indicate flow velocity?
By measuring the elongation ratio, which increases with flow velocity
An elongation ratio greater than 1 indicates a more elongated feature.
What are Mega-Scale Glacial Lineations (MSGL)?
Subtle elongated features in the landscape, indicating rapid ice flow
They can also be found in submarine environments and are linked to ice streaming.
What does the continuum of glacial landforms include?
- Ribbed moraines
- Drumlins
- Mega-scale glacial lineations (MSGL)
These landforms suggest a continuum related to ice dynamics and flow conditions.
What is the significance of understanding glacial landforms?
Helps reconstruct the dynamics of past ice sheets
Knowledge of processes and forms allows for interpretation of historical glacial activity.
