Glaciation Flashcards
When was the last ice age
About 18,000 years ago
What do ice ages have and what are these called
Intermittent warm periods, called interglacials
Definition of a glacier
Slow moving rivers of ice
An example of a European glacier
Mer de glace, France
Definition of ice sheets
The large areas of thick ice found in Antarctica and Greenland
Definition of ice caps
Smaller areas of thick ice
Definition of crevasses
Cracks in the ice
The glacier system consists of what
Input, transfers (flows), stores and outputs
Where do inputs come from
From avalanches along the sides of the glacier but mainly from precipitation as snow
What happens to snow over time and where is it stored
Snow accumulates and is pressed into ice, the water held in storage is the glacier
Under the force of gravity the glacier flows where
Downhill
What is the main output from the glacier along with some evaporation
Meltwater
What is an iceage
A period when there is long term reduction in the temperature resulting in the presence or expansion of ice
What does the the balance between inputs and outputs do
Vary
In winter what do inputs normally do
Exceed outputs near to the head of the glacier (accumulation)
Where does the glacier advance
Near the head
In the summer and at lower altitudes what exceeds what
Outputs will exceed inputs (ablation), here the glacier retreats
What are most of the worlds remaining glaciers doing
Retreating
Processes that operate in the glacier system:
1- frost shattering
First step
Water finds its way into small cracks in the rock
Processes that operate in the glacier system:
1- frost shattering
Second step
At night, when temp drops to 0 degrees or below, the water freezes. The water expands as it freezes creating huge forces on surrounding areas of the rock. During the day when temp warms up the frozen water thaws
Processes that operate in the glacier system:
1- frost shattering
Step 3
This process is repeated over and over, causing oh her cracks in the rock
Processes that operate in the glacier system:
1- frost shattering
Step four
This process this is called frost shattering or freeze thaw weathering. It provides the main source of material for glaciers to use in erosion
Processes that operate in the glacier system:
2- abrasion
The material frozen into the glacier scours the valley sides and base. This is a sand-papering effect similar to corrasion by a river but on a far larger scale
Processes that operate in the glacier system:
3- plucking
The water at the bottom of the glacier freezes onto rock on the valley base. As the glacier moves the rock is pulled away from the valley base. Plucking normally occurs when the rock is well jointed
Landforms created by glacial erosion
1: corrie
First point
Snow collects in a natural hollow on the side of a mountain. Over time further snow collects in the hollow. This extra weight compresses the snow underneath, turning it into ice
Landforms created by glacial erosion
1: corrie
Second point
The is deepened and widened by the processes of abrasion and plucking
Landforms created by glacial erosion
1: corrie
Point 3
This leads to an ‘armchair’ shape and causes a ‘rock lip’ to be formed
Landforms created by glacial erosion
2: Arête
An arête is a very narrow ridge on a mountain and is sometimes described like a knife edge
Landforms created by glacial erosion
3- pyramidal peak
A pyramidal peak is an angular sharply pointed mounted peak in which results from corrie erosion due to multiple glaciers diverging from a central point
What is an example of a pyramidal peak
The matterhorn in the Alps
Definition of glacial trough/ u shaped called
This is when glaciers cut distinctive u shaped valleys with a flat floor and steep sides
Definition of a truncated spur
As the valley glacier moves, abrasion and plucking, erode the protruding tips of the Spurs, leaving the, truncated
Definition of a hanging valley
This is a side valley that enters a main valley at a height, high above the main valley floor
Definition of a misfit stream
This is a stream that is too small to have eroded the u shaped valley in which it flows
Landforms created by glacial deposition:
1- moraines
Moraine is a type of landform that is created when a glacier deposits the material (till) that it has been transporting
Landforms created by glacial deposition:
List 5 types of moraine
Lateral Medial Ground Recessional Terminal
Landforms created by glacial deposition:
2- drumlins
Drumlins are formed of till. They are elongated features that can reach a kilometre in length or more, 500m or so in width and over 50m in height.
Landforms created by glacial deposition:
What is a collection of drumlins called
A swarm
Landforms created by glacial deposition:
3- Glacial stritations
Scratches or gouges cut into bedrock by glacial abrasion
The features of glacial deposition:
Ground moraine
This is moraine that is dragged Beneath a glacier and forms part of the valley floor
The features of glacial deposition:
Lateral moraine
This is moraine that is produced from frost shattering of the valley sides and is carried at the sides of the glacier
The features of glacial deposition:
Terminal moraine
This is moraine found at at the snout (end) of the glacier and marks the maximum advance of a glacier
Material that’s deposited and shows maximum advance of glacier and glacier retreats
The features of glacial deposition:
Medial moraine
This is moraine found at the centre of a glacier
The features of glacial deposition:
Recessional moraine
This is moraine that marks interrupt ions in the retreat of a glacier
The features of glacial deposition:
Erratics
This is a boulder that is different to the bedrock upon which it is sitting. They have been transported and deposited by a glacier. Therefore erratics are useful indicators of patterns of former ice flow
Landforms as a result of erosion and deposition:
Ribbon lake
These are narrow lakes, found on the valley floors of glacial troughs
Landforms as a result of erosion and deposition:
How is a ribbon lake formed
When a glacier moves along its valley, areas of softer rock may be eroded more easily. When a glacier retreats, deepened sections fill with melt water and become lakes. Deposition of moraine, across the valley, can also act as a dam, trapping the meltwater and there by, creating a ribbon lake
Landforms as a result of erosion and deposition:
Avalanches…
What is an avalanche
A mass of snow and ice that moves very rapidly down a mountainside
Natural causes of avalanches
In the spring melting weakens the layers of ice and snow causing them to become unstable
A small earthquake
Human causes of avalanches
People skiing and snowboarding
Case study - Galtur Austria (Avalanche)
When
Tuesday 23rd of February 1999
Case study - Galtur Austria (Avalanche)
Where
In Galtur, in a small village in the Austrian Alps
Case study - Galtur Austria (Avalanche)
Consequences of this Avalanche
8 dead
Leading up to 30 missing
Tens of thousands stranded, in train stations, traffic jams, and isolated resource towns across France, Switzerland, Italy and Austria, as the avalanche buried roads, homes and railways
Helicopters couldn’t get in due to bad weather
People rescued were badly injured
Ways to reduce the hazard of avalanches
by building wooden fences to hold back the snow
Trees hold the snow pack together
Trees will break up smaller avalanches, preventing them from becoming too dangerous
Roads and buildings at risk can have shutes built to protect them
Second definition of an interglacial
A period of time between one iceage and another
What percent of the planet was covered in ice during the last ice age
30%
What do glacial stritations indicate
The direction of ice
