Glaciers Theory Flashcards
What is the Cryosphere?
Consists of ice sheets and glaciers, together with sea ice, lake ice, permafrost and snow cover.
Explain eccentricity cycles?
The orbit changes from circular to elliptical over 100,000 year cycles.
Explain Axial Tilt cycles?
Tilt of the Earth’s axis varies between 21.5° and 24.5° over 41,000 year cycles.
Explain wobble cycles?
The earth wobbles as it spins which means that the area of earth nearest the Sun varies. Varies over 21,000 year cycles.
Explain sunspots.
Cause more radiation = more heat = higher temperatures. Occur on an 11 year cycle.
Explain volcanic causes of climate change?
Volcano erupts = more ash in atmosphere = blocks radiation = less heat = earth cools
Happens every 5-10 years
When was the last glacial maximum?
18,000 years ago (Loch Lomand)
What happened in the Loch Lomand Stadial?
-11,500 years ago temps dropped by 6-7°c
- Glaciers re advanced across the UK especially the Scottish Highlands
When was the Little Ice Age?
Between 1550 and 1750
What were some impacts of little ice age?
- Glacial advancement
- Artic Sea spread to Iceland (polar bears)
- Stopped advancing due to industrial revolution
What is an Ice Sheet and where is it found?
Complete submergence of topography with ice several km thick
Greenland
What is an Ice Cap and where is it found?
Small version of ice sheet on upland areas
Vatnajökull, Iceland
What is an Ice Field and where is it found?
Ice covering an upland area, but not thick enough to bury topography.
Patagonia, Chile
What is a Valley Glacier and where is it found?
Glacier found between a valley
Athabasca, Canada
What is a Piedmont glacier and where is it found?
Valley glacier that extends past a mountain onto flat surface and fans outwards
Mauaspina, Alaska
What is a Cirque glacier and where is it found?
Small glacier occupying hollow on mountain side
Hodges glacier
Georgia
What is an Ice shelf and where is it found
Large area of floating glacial ice extending from coast
Ronne and Ross, Antarctica
Name 3 inputs of glacial systems (accumulation)
- Rock Debris
- Peecipitation
- Avalanches from above
Name 3 outputs of glacial systems (ablation)
Meltwater
Calving
Evaporation (sublimation)
What is aspect?
can determine the amount of snow falling. In the northern hemisphere, north and east facing slopes are more sheltered and shadier.
What is permafrost?
Soil and rock that remains frozen as long as temperatures do not exceed 0°c during the summer months for 2 consecutive years.
How is an ice wedge formed?
Frost cracking creates areas of irregular polygons, 5-30m across.
Active layer thaws = water gets in = freeze thaw.
How does patterned ground form?
Frost push propels stones upwards
Frost heaven cause stones to migrate outwards
How do closed system pingos form?
- Continuous permafrost
- Lake with sediment underneath, as the lake freezes over the sediment is pushed up forming the Pingo
How do open system pingos form?
- Discontinous
- Active layer freezes and the moisture forms an ice lens. Water from deeper underground is attracted to this due to hydraulic pressures and therefore moved towards it and freezes
- This grows bigger and makes a pingo
How do blockfields form?
In Situ, created by frost heaving of jointed bedrock and freeze thaw weathering
How do Tors form?
Areas of more resistant rock remain where as the less resistant rock gets broke through freeze thaw and frost heave
How do scree slopes form?
When rock fragments fall and accumulate on lower slopes/ cliff bases
How do solifluction lobes form?
During summer months the active layer melts forming mobile water trapped under the soil.
This moves and forms lobes that can be seen on a slope
How do pro-talus ramparts form?
Created if a patch of snow has settled at the base of a cliff. When rocks fall, snows acts as a barrier which then leaves a rampart of boulders when snow melts.
How do nivation hollows form?
Occurs when weathering and erosion takes place under a snow patch which then causes hollows to form when snow melts.
How do Asymmetric Valleys form?
Different rates of solifluction and frost creep lead to one side of a valley being a lot steeper than another.
What is continuous permafrost?
- Temps are below -6°c all year
- Found at highest latitudes
- Extends downwards hundreds of metres
What is sporadic permafrost?
- Annual temps just below freezing
- covers less than 50% of the landscape
What is discontinuous permafrost?
- Shallower and permanently frozen ground is fragmented
- Surface layer melts during summer
What is frost heave?
The freezing and expansion of soil causes rocks to become loose. As water freezes and expands these rocks are pushed towards the surface.
What is solifluction?
The downslope movement of saturated active layers under gravity.
What is Nivation?
A combination of processes that weaken and erode the ground beneath the snow patch.
What is groundwater freezing?
Water filters underground and freezes causing the ground to heave upwards into a dome
What is Aeolian action?
Wind related
What is negative feedback?
4 points
1) Increased snowfall on a glacier
2) more snow enters ablation zone as glacier advances
3) snow in ablation zone melts
4) glacier back to normal
What is positive feedback?
4 points
1) Glacier has a positive mass balance (increasing)
2) Increase in ice albedo
3) Further reduction in air temp
4) Accumulation increases
What is Basal slip?
- Pressure builds at base making a PMP
- Ice melts at PMP to form a lubricant between bedrock and ice
- Glacier can slide down
- 20-30m a day
What is Regulation creep?
- High pressure and friction causes heat to build at an obstacle
- Glacier melts and meltwater flows around obstacle
- Glacier refreezes other side
What is internal deformation?
- cold based glaciers = attached = can’t move in one go
- crystals orientate themselves in direction of ice flow
- crystals slowly move past eachother
- 2-3m per day
What is extending flow?
As ice flows over a steep gradient it goes faster and becomes thinner.
What is compressional flow?
as ice flows over a gentle gradient it slows and thickens
What is a surge?
When extensive meltwater builds beneath a glacier causing a surge in movement?
300m a day
How is a cirque formed?
5 points
1) Glacial ice forms in hollow in ground
2) Ice moves via rotational slip which causes abrasion
3) Plucking occurs
4) Abrasion eroded bedrock
5) As this continues the Randkluft is created which makes a steeper cliff wall
What is a lateral moraine?
Sharp piles of glacial sediment that are deposited as ice melts. Found on sides of glaciers.
What is a Medial moriane?
found on top of glacier. 2 lateral moraines pushed together when glaciers meet
What is a supraglacial moraine?
material on the surface of the glacier that has fallen there due to natural causes
what is a terminal moraine?
forms at the end of a glacier when all debris is pushed in front of a glacier and is deposited
What does fluvioglacial mean?
Created by meltwater
How does an esker form?
Subglacial channels become obstructed leading to the deposition and build up of material.
How does a Kettle hole form?
Ice blocks fall onto ground and leave a depression once they melt?
How does a proglacial lake form?
Meltwater collects at end of glacier due to ridges created by moraines dam the meltwater in.
How do Kame Terraces form?
Mounds of sediment get deposited by the glacier along the valley sides.
How to Kame delta’s form?
Subglacial river meets a subglacial lake = river velocity reduces = sediment is deposited where the river meets the lake
How do outwash plains/ Sandurs form?
Sediment exits the snout of a glacier = velocity is reduced = sediment is dropped
What is a relict environment?
no ice, not experiencing glacial activity. but contains features of glacial landforms
What is an active environment?
An environment currently experiencing glaciation
Name 5 economic factors to glaciated landscapes
- tourism
- HEP
- Farming
- Mining
- Forestry
What is artic amplification? 3 steps
1) As ice melts, less sun gets reflected into space (albedo)
2) Permafrost melting releases greenhouse gases
3) Less snow = less rock’s cover = more heat absorbed from sun
What is an avalanche?
When sheer stress exceeds sheer strength of mass of snow located on a slope.
What is a glacial flood outburst?
A powerful flood caused by the sudden discharge of a sub glacial or ice moraine dammed lake.
List 3 impacts of global warming?
1 - Ice Melting
2 - Sea levels rising
3 - Warmer weather
What is total exploitation?
Maximum economic exploitation without any protection of natural environment
Often preferred by businesses
What is sustainable exploitation?
Attempts to find a balance between the need for resource exploitation and economic growth, and the need to conserve the natural environment.
What is total protection?
aims to completely conserve the natural environment, maintaining pristine conditions with the only form of exploitation being limited scientific research
