Glaciated Landscapes SG1 Flashcards
Define Glacier
A land based ice mass that is thick enough to ‘flow’ under its own weight
Define Glaciated Landscape
Landscapes that have been shaped by the action of glaciers (current and past glaciers)
Define Valley Glacier
River of ice which flows down from high mountains, following the course of existing river valleys
How long are valley glaciers?
10-30km
Define Ice Sheet
Areas of thick ice spread out over land and sea
How far do ice sheets extend for?
> 50,000km3
What % of today’s ice is in ice sheets?
69%
What % of the earth is covered by ice?
10%
What is the last glacial period called?
The Pleistocene
How long ago was the Pleistocene?
2 million - 11,000 years ago
What is the current interglacial period called?
Holocene
When did the Holocene start?
11,000 years ago (at the end of the Pleistocene)
Define Ice Age
An extended period of time where the earth experienced a cycle of very cold phases (glacials), interspersed with warmer phases (interglacials)
Define Glacial
A very cold phase where global temperatures dropped by approximately 5 degrees C resulting in the spread of ice
Define Interglacial
Warm phase where temperatures increased to present level or above
Define Accumulation
Input of snow and ice to a glacier
Define Ablation
The loss of ice and snow through melting, evaporation and sublimation
Define Equilibrium Line
Balance between inputs and outputs
Define Net Balance
Difference between accumulation and ablation
Define Glacial Mass Balance (or Budget)
The difference between the amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year period
Is the glacial mass balance positive or negative in winter?
Positive - accumulation exceeds ablation
Is the glacial mass balance positive or negative in summer?
Negative - ablation exceeds accumulation
Define System
A set of interrelated elements comprising of components (stores) and processes (links) that are connected together to form a working unit
What three things does a glacier comprise of?
Inputs, Throughputs/Processes, Outputs
Define Potential Energy
Energy stored in the glacier’s height
Define Kinetic Energy
The capacity to do work as a result of motion
Define Thermal Energy
The capacity to do work as a result of heat
Define Diagenesis
How snow turns into ice
Where are cold based glaciers found?
At high latitude locations and in places of low relief
Where are warm based glaciers found?
At high altitude locations and in places of high relief
What is another name for a warm based glacier?
Temperate glaciers
What is another name for a cold based glacier?
Polar glaciers
What is the velocity of warm based glaciers?
20m to 200m per year
What is the velocity of cold based glaciers?
Only a few meters per year
Define Pressure Melting Point
The temperature at which ice is at the verge of melting, at a given pressure
What is the main movement of warm based glaciers?
Basal sliding
What is the main movement of cold based glaciers?
Internal deformation
What are the three mechanisms of basal sliding?
Slippage, Regelation, Substrate deformation
Define Slippage
If the basal temperature is above pressure melting point a thin film of melt water exists between the glacier and valley floor so friction is reduced
Define Regelation (or Creep)
On the up-valley side of an obstruction the ice will have increased pressure, creating higher temperatures. This causes the ice to deform around the obstruction. It refreezes on the downhill side
Define Substrate Deformation
When meltwater is present beneath a glacier it can seep into any sediment below. When the sediment becomes saturated it will act as a lubricant and the ice will slide on it
What are the two mechanisms of internal deformation?
Intergranular slip, Laminar flow
Define Intergranular Slip
The overlying weight of ice can result in the individual ice crystals changing shape due to compaction. Ice crystals become flattened and so slide over each other
Define Laminar Flow
The layers of snow, firn, neve and glacial ice create planes of weakness. This combined movement allows the ice to move down-slope under the effect of gravity
Define The Rigid Zone
The upper zone of the glacier where the ice is brittle and breaks
Define The Plastic Zone
The lower zone of the glacier where under the pressure the ice deforms
Define Extending Flow
When ice moves over a steep slope it is unable to deform quickly enough so it fractures forming crevasses. The leading ice pulls away from the ice behind it
Define Compressing Flow
When the gradient decreases, ice thickens and the flowing ice pushes over the slower moving leading ice
Define Closed System
Have transfers of energy into and beyond the system but not matter
Define Open System
Have transfers of matter and energy beyond the system
Are glaciers open or closed systems?
Open
Define Dynamic Equilibrium
A state of balance between continually changing processes
Define Negative Feedback
Acts to minimise or dampen the effect on change
Define Positive Feedback
Acts to reinforce or amplify the effect on change
What are the three physical factors affecting glaciated landscape systems?
Climate, Latitude and Altitude, Relief and Aspect, Geology
