Glaciation Flashcards
What is carbon dating?
Using radioactive testing to find the age of rocks which contained living material
What is erosion?
The wearing away of a landscape
What is an eon?
A basic unit of geological time in which a single type of rock system is formed
What is an epoch?
A subdivision of the geologic timescale that is longer than an age and shorter than a period
What is geology?
An earth science comprising the study of solid earth, the rocks it is made up of and the processes by which they change
What is glaciation?
A cold period of time when the earth’s glaciers expanded widely
What is strata?
Horizontal layers of rock
What was snowball earth?
A deep freeze around 715 million years ago which lasted around 120 million years
What are the Milankovich cycles?
-Eccentricity = elliptical orbits mean the earth is either very far from or close to the sun causing melting periods, this changes every 100,000 years
-Wobble = wobbles to create a circular orbit every 21,000 years causing mild winters and cooler summers
-Tilt = changes its axis from 21.5 to 24.5 degrees every 41,000 years which can cause much hotter summers and much colder winters
What are solar variations?
They are sunspots on the earth’s surface showing that the sun is more active that usual, if there are more emissions it can increase the earth’s average temperature
What are volcanic eruptions?
They release ash and sulphur dioxide gas and when they reach the atmosphere they reflect solar energy and prevent it reaching earth
What are meteorological processes?
Determines why some areas have ice cover
-polar glacial dry low temperatures
-low precipitation due to high pressure
-alpine areas
What is the cryosphere?
Part of the earth’s crust and atmosphere that are subject to temperatures below 0 degrees for at least part of the year
e.g ice sheets or glaciers
What is the hydrological cycle?
The movement, transfer and storage of water around the world
How does ice affect the hydrological cycle?
Maintains a freshwater store
Why is the cryosphere important?
-Provides habitat
-Large freshwater supply
-Allows for research purposes
-Affects sea levels and currents
What ways can we classify different ice masses?
-Thermal characteristics = whether it is warm or cold based
-Morphology of the land = studying the characteristics, origin and development of the landforms
-Degree of constraints = is the glacier hemmed in by valleys or not
What is a warm based (temperate) glacier?
-Water is present throughout the ice mass and acts as a lubricant
-This allows greater rates of movement and erosion
-They are often found at mountain glaciers at lower latitudes and higher altitudes
What is a cold based (polar) glacier?
-They occur in high latitudes where snowfall is below 0 degrees and the glacier is 0 degrees all year
-The glaciers stay frozen all year so there is little ice movement and little erosion
What is a cirque glacier?
Small and occupy armchair shaped hollows on mountains and can over spill to feed valley glaciers
What is a piedmont glacier?
A valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out
What does periglacial mean?
Areas at the edge of permanent ice characterised by permafrost and tundra environments
What is permafrost?
Where a layer of soil, sediment or rock below the surface remains permanently frozen
-it can reach depth of 400 to 500 metres
-e.g Russia, Greenland, Canada
What is an active layer?
The top soil in permafrost environments that thaws during summer and freezes during the winter
What are the three types of permafrost?
-Continuous = in the coldest regions with little thawing in the summer
-Discontinuous = slightly warmer and doesn’t penetrate as deeply
-Sporadic = temperatures are around freezing and it happens when the climate is cold enough to prevent thawing in the summer
Which factors influence the distribution of permafrost?
-Climate = determines the depth and extent of the permafrost
-Vegetation cover = prevents sunlight reaching the ground
-Snow cover = reflects sunlight so no sun reaches the ground
What is mass balance?
The net gain or loss of ice in a glacier over a specific period
What is dynamic equilibrium?
When outputs and inputs are balanced
What is sublimation?
The transition of a substance directly from the solid state to the gas state without passing through the liquid state
What is internal deformation?
-Inter granular movement moves the individual ice crystals over each other
-This causes the ice crystals to become deformed or fractured due to stress within the ice
-The ice movement can then form crevasses
-Happens in warm and cold based glaciers
What is accumulation?
Any process increasing the mass of the glacier
What are feedback loops?
Deviations in inputs or outputs that move systems away from their equilibrium
How does ice form?
-Snowflakes fall and accumulate, this is made of loose snow which is 90% air
-The ice compacts and the flakes undergo pressure, this causes granular snow which is 50% air
-This continual compaction produces firn forming glacial ice with trapped air making it blue, this made of firm snow which is 25% air
What is a crevasse?
A deep v-shaped cleft formed in the upper part of a glacier as a result of the ice undergoing extension
What is ablation?
Any process that decreases the mass of the glacier
What is negative feedback?
Regulates systems to maintain the balance and equilibrium
What is positive feedback?
Enhances and speeds up the processes promoting rapid change
What is basal slip?
-Meltwater acts as a lubricant reducing friction with the bedrock and debris
-Happens in warm based glaciers
-Is accountable for 75% of warm based glacier movement
What is plucking?
A form of erosion which pulls away pieces of rock as the glacier moves
What is a macro-scale landform?
Large scale landforms that have been created by a combination of glacial processes over a period of time
e.g cirques, aretes
What is a meso-scale landform?
An intermediate scale landform that has been created mostly by erosion and meltwater erosion
e.g drumlins, roche moutonees
What is a micro-scale landform?
Small scale landforms
e.g striations, erratic
What does sub glacially mean?
Moving material to the base and sides, happens mostly in meltwater
What does en glacially mean?
Moving material within the glacial ice
What does supra glacially mean?
Transporting material on top of the ice
How does a glacial trough form?
Glacial troughs are U-shaped valleys carved out by the erosive action of glaciers
How does a hanging valley form?
Form when smaller glaciers in the tributary valleys are unable to erode as deeply as the larger, main glacier
How does a truncated spur form?
There are ridges which were cut off by the erosive action of the glacier
How does an arete form?
Narrow ridges forming between two adjacent glacial valleys due to erosive actions of glaciers on both sides of the mountain ridge
What is a pyramidal peak?
Pointed, steep-sided mountains with three or more faces forming at the intersection of multiple areas due to glacial erosion on the mountain
What is till?
Mixed or unstratified material deposited by the ice
What is lodgement till?
Occurs beneath the ice mass when friction between the debris and the bed gets stuck and the glacier moves past it
-results in more rounded and smooth till due to abrasion
What is ablation till?
Debris dumped as the glacier melts and thaws
-results in more angular rocks as they do not experience abrasion
What is terminal moraine?
Where the front of the glacier was, shows the furthest the glacier travelled
What is recessional moraine?
The point the glaciers snout reached before the glacier started to retreat
What is an erratic?
Boulders transported and deposited by a glacier
What is a moulin?
A circular, vertical, well-like shaft within a glacier trough which water enters from the surface, it carries meltwater from the surface down to wherever it may go
What makes Antarctica special?
-Remote continent on earth
-Coldest, windiest, least populated
-Smallest continent except from Oceania
-Gigantic ice sheet
-Coldest temperature recorded was -89.2 degrees
What are the economic values of glacial environments?
-Farming = provides high slopes, high precipitation, low temperatures where sheep can be moved in the summer allowing the grass to recover e.g in the UK
-Forestry = involves researching tree types to understand different plant species
-Mining and quarrying = there are oil and gas stores in the rock beneath the ice sheet e.g the Antarctic
-Hydroelectricity = created by increasing the pressure of water flow through a turbine producing electricity e.g Switzerland
-Tourism e.g the Swiss Alps
What is polar tourism?
-Started around 170 years ago
-1991/92 had around 64,000 visitors
-74,000 passengers visited in 2019/20
-There were 8x as many operators before the pandemic than there were in 1991/92
-60 ships and 408 cruises which travel there
How does an avalanche happen?
A grinding motion starts and rapidly accelerates on slopes of more than 30 degrees
What are lahars?
-The most destructive volcanic events
-They are a mixture of water, volcanic ash, tephra, rock fragments and chunks of ice
-1985 eruption in Columbia
What is geomorphology?
The study of the physical features of the surface of the earth and their relation to its geological structures
What is uniformitarianism?
A concept which suggests that catastrophic (biblical) processes were not responsible for the landforms that exist on earth’s surface
-it was developed by James Hutton in 1785
-suggests that supernatural theories were not needed to explain the geological history of the earth
What is a polycyclic landscape?
A concept that most glacial regions are produced by a series of glaciated periods in one area
What is a corrie?
A round hollow in the side of a hill
What is a pingo?
A mound produced as ground is forced upwards through frost heave
What is frost heave?
The freezing and expansion of water beneath the ground resulting in floor uplift
What is a roches moutonnees?
A rock shaped by the glacier flowing over it and eroding it
What is basal sliding?
Glaciers sliding over bedrock due to meltwater between the two surfaces
What is a drumlin?
When a glacier hits an obstacle that cannot be eroded so deposition from underneath the glacier builds up behind the obstacle
