Glacial Processes Flashcards
to be able to explain glacial processes, including weathering, erosion, movement, transportation and deposition.
What type of weathering is freeze-thaw weathering?
Physical/mechanical weathering
What type of environments is freeze-thaw weathering commonly found?
Mountainous/Cold environments
What is the name of the debris created by freeze-thaw weathering?
Scree
Define weathering
Weathering is the break-down of rock in situ (ie no movement) by the process of the weather. The glaciers do not have anything to do with this process. This happens on the slopes above the glacier.
Define erosion
The wearing away and removal of the land by flowing water, ice or wind.
What is abrasion?
Abrasion is where rocks at the bottom of the glacier act like sandpaper - grinding over the bedrock. This can polish the rocks or create sharp grooves called striations.
What are striations?
Sharp grooves created by the process of abrasion.
What is plucking?
Plucking is where a glacier moves over an area of rock. Due to friction, the glacier melts and water seeps into cracks around the rocks below. The water refreezes and the rock effectively becomes part of the glacier and is ripped out when the glacier continues to move forward.
What is the name of young ice?
Firn/Neve
Explain the process of freeze-thaw weathering
- Joints in the rock fill with water.
- The water freezes and expands and over time this splits the rock apart.
- Repeated freezing and thawing widens the crack and eventually bits fall off to create scree.
How does a glacier move?
- Gravity
- Basal Flow: It slides over the underlying rock on a film of meltwater in a process called basal flow.
- Internal deformation.
What is internal deformation?
The ice moves as if it were plastic, oozing along, speeding up and slowing down in response to changes in the gradient of the slope below.
Where does the initial accumulation of snow take place?
Shady north-facing hollows in upland areas (where winter snow can survive without melting through the summer months).
Explain how snow is converted into glacier ice over time.
- Snow falls in layers.
- Over time the layers become compressed - as the air is squeezed out of the layers.
- Firn or neve is formed.
- As the weight of the snow and ice above increases all of the air is squeezed out leaving only ice.
What is basal flow?
A film of meltwater develops due to pressure melting at the base of the glacier which is basal flow.
What is bulldozing?
Ice pushes material of all shapes and sizes as it moves slowly forward (at the snout)
What is glacial outwash?
Material, mainly sand or gravel, deposited by meltwater streams in front of, and underneath, a glacier. The material is sorted and rounded by water action.
Which erosional processes has reduced the size of outwash material?
Attrition
Where would you expect to find the fine material deposited by the glacier - closest or furthest away from the glacier?
Furthest from the glacier.
What is till?
An unsorted mixture of sand, clay and boulders carried by a glacier and deposited as ground moraine over a large area.
What is moraine?
Frost-shattered rock debris and material eroded from the valley floor and sides, transported and deposited by glaciers.
