Glaciers - Enquiry Question 1 Flashcards
1
Q
Pleistocene period
A
A geological period from about 2 million years ago to 11,500 years ago, the early part of the quaternary which included the most recent age
2
Q
Greenhouse conditions
A
Much warmer interglacial conditions
3
Q
Interglacials
A
Warmer periods similar to present, i.e. greenhouse periods
4
Q
Glacials
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Cold, ice-house periods within the Pleistocene
5
Q
Ice-house conditions
A
Very cold glacial conditions
6
Q
Types of cold environments
A
- Polar
- Alpine
- Glaciers
- Periglacials
7
Q
Polar environments
A
- Glacial environments are found in the high latitudes of the Antarctic and Arctic
- They are characterised by extremely cold temperatures (average annually of -30 to -40°C and low levels of precipitation)
8
Q
Alpine environments
A
Glacial environments are found at high altitudes in mountain ranges in the mid-low latitudes, e.g. European Alps, the Himalayas and Andes
- They are characterised by high levels of precipitation and a wide temperature range with frequent freeze-thaw cycles
9
Q
Glacier environments
A
These are slow-moving bodies of ice in valleys, which shape the landscape in both polar and alpine environments
10
Q
Periglacial environments
A
- These environments do not feature glaciers, but are usually found next to glacial areas
- They are characterised by permafrost and occur in high latitude areas where seasonal temperatures vary above and below freezing point, e.g. Siberia, Alaska and northern Canada
- Can be 3°C to -50°C
- Low biodiversity
11
Q
What are the longest span of geological time?
A
Eons (typically around 1 billion years old)
12
Q
What are the second longest span of geological time?
A
Eras
13
Q
Ice Age/Pleistocene epoch
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The Pleistocene epoch is often known as the ice age as it contained 50 glacial-interglacial cycles and glacials reached their furthest extent in this time
14
Q
Devensian
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The last glacial maximum is known as the Devensian which was 18,000 years ago
15
Q
What was the last UK glacial advance?
A
- The last UK glacial advance was called the Lock Lomond Stadial which was 12,000 to 10,000 years ago and marked the end of the Pleistocene epoch
16
Q
The UK is now called a relict glacial environment. What is meant by this?
A
It no longer experiences glacial conditions but it does display evidence of the Pleistocene glaciation period
17
Q
How many years ago was the start of the Pleistocene?
A
2.6 million years ago
18
Q
The Devesian glacial ended how many years ago?
A
18,000 years ago
19
Q
The end of the Pleistocene/start of the Holocene was how many years ago?
A
11,500 years ago
20
Q
How long did the Loch Lomond Stadial last?
A
10,000-12,000
21
Q
Long term causes of climate change
A
- Continental drift
- Eccentricity of the orbit (Milankovich cycles)
- Axial tilt
- Wobble
22
Q
Short term causes of climate change
A
- Variations in solar output/sunspots
- Volcanic causes (eruption theory)
23
Q
Continental Drift
A
3 million years ago, the North and South American tectonic plates collided. This re-routed the ocean currents to that warm Caribbean waters were forced northwest, creating the Gulf Stream
24
Q
Eccentricity of the orbit
A
The shape of the Earth’s orbit varies from circular to elliptical over 100,000 year cycles. The Earth receives less solar radiation in the elliptical orbit when the Earth is farthest from the Sun (a position known as the aphelion)
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Axil tilt
The tilt of the Earth's axis varies between 21.5° and 24.5° over 41,000 year cycles. This changes the severity of the seasons
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Wobble
The Earth wobbles as it spins on its axis, which means that the season during which the Earth is nearest to the Sun (a position known as the perihelion) varies. At present, the northern hemisphere winter occurs in perihelion. i.e. milder conditions than previous winters in aphelion. This varies approximately 21,000 year cycles, resulting in changes in the intensity of the seasons
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Variation in solar output
The dark areas of the Sun (sunspots) are cuased by intense magnetic activity in the Sun's interior. An increase in the number of sunspots means that the Sun is more active and giving off more energy. They appear to vary over an 11 year cycle
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Volcanic causes
Large eruptions can eject huge volumes of ash, sulfur dioxide, water vapour and carbon dioxide into the atmosphere (volcanic aerosols) which are globally distributed by winds. This aerosol blocks the Sun's radiation, cooling the Earth. The ash tends to settle back on Earth within a few months, however the sulfur dioxide gas can remain in the atmosphere for up to 3 years, which reflects the radiation back into space
29
Loch Lomond Stadial (the Younger Dryas event)
- Ice sheets began retreating about 18,000 years ago, with rapid deglaciation by 15,000 years ago (late glacial interstadial) with similar temperatures as today leading to widespread distribution of deciduous woodlands across Europe
- However, around 12,500 years ago the temperatures plunged downwards and, by 11,500 years ago, glacial conditions occurred with temperatures 6-7°C lower
- Glaciers re-advanced in many parts of the world including the formation of ice caps in Scottish Highlands, from which cirque and valley glaciers flowed outwards, with smaller areas of cirque glaciers in the Lake District and North Wales
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The Little Ice Age (Holocene)
Between 1350 and 1900, conditions were slightly colder - perhaps on average by between 1.0°C and 2.0°C - than at present over much of the globe
- Between 1550 and 1750 there was a low trough of very cold conditions, known as the Little Ice Age, which occurred globally
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Impacts of the Little Ice Age
- The widespread abandonment of upland farms in Scandinavia and Iceland
- Many glaciers in Europe re-advanced down valleys; the Little Ice Age was a period of predominantly positive net mass balance leaving prominent terminal moraines from which the glaciers subsequently retreated, but often at different dates/ times around the world
- Arctic Sea ice spread further south with polar bears seen frequently in Iceland
- Rivers in the UK and lowland Europe, and New York habour, froze over
- Curling developed as a national sport in Scotland as there were so many frozen lakes and rivers
- In Chamonix Valley, France (near Mont Blanc), farms and villages were lost to the advancing front of a nearby mountain glacier
- Crop failures in N. Europe
- Increased cases of famine, disease and child mortality in Europe (17th-19th century)
- In London, where the Thames had frozen over, winter carnivals/markets were held
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Cryosphere
- The cryosphere consists of ice sheets and glaciers, together with sea ice, lake ice, permafrost and snow cover
- Mass and energy are constantly exchanged between the cryosphere and other major components of Earth systems; the hydrosphere, lithosphere, atmosphere and biosphere
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Glaciers
- Glaciers are large bodies of ice which flow downhill under the influence of gravity
- Some are land based and their base is at or above sea level e.g. Mer de Glace flows from Month Blanc in the Alps, or glaciers flowing from the Rocky Mountains
- Others are marine bases, where the base is below sea level, e.g. the West Antarctica Ice sheet - which is 2000m below sea level, and is actually frozen to the sea bed
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Warm based glacier
Occur in high altitude areas outside the polar regions e.g. the Alps. The temperature of the ice is often close to zero and mild summer temperatures cause melting
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Cold based glaciers
These occur in polar glacial environments such as Greenland and Antarctica. These glaciers are frozen onto the bedrock below and melting only occurs on the surface in the summer months
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Ice sheet
- Complete submergence of regional topography; forms a gently sloping dome of ice several kilometres think in the centre
- 10-100,000 sq km
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Ice cap
- Smaller version of ice sheet occupying upland areas; outlet glaciers and ice sheets drain both ice sheets and ice caps
- 3-10,000 sq km
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Ice caps
- Ice covering an upland area, but not hick enough to bury topography; many do not extend beyond highland source
- 10-10,000 sq km
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Valley glacier
- Glacier confined between valley walls and terminating in a narrow tongue; forms from ice caps/sheet of cirques; may terminate in sea as a tidewater glacier
- 3-1,500 sq km
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Piedmont Glacier
- Valley glacier which extends beyond the end of a mountain valley into a flatter are and spreads out like a fan
- 3-1,000 sq km
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Cirque glacier
- Smaller glacier occupying a hollow on the mountain side carves out a corrie, cwm or cirque; smaller version is known as a niche glacier
- 0.5-8 sq km
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Ice shelf
- Large area of floating ice extending from the coast where several glaciers have reached the sea and merge
- 10-100,000 sq km
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The Glacial System
Glaciers gain mass through the transformation of snow into ice and then flow downhill (in response to gravity) and eventually lose mass due to melting, Hence glaciers can be viewed as systems with inputs, stores, transfers and outputs
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What is an input?
- Something going into the glacial system, e.g. snow builds up overtime, pressure compresses air out of it and it becomes ice
- Can be sediments carried by the snow
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What is an output?
Something that leaves the glacier, main output = meltwater
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Examples of accumulation (inputs)
- Avalanches from slopes above
- Rock debris
- Wind deposition
- Meltwater
- Precipitation (mainly snow)
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Examples of ablation (outputs)
- Evaporation (sublimation)
- Break away of ice blocks and ice bergs (calving)
- Rock debris
- Melting (water) - during the summer months
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Glacial budget
A glacier mass balance/annual budget is calculated using the total accumulation and ablation within a year (at what rate is it increasing or decreasing in size?)
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Sublimation
The process of a substance turning into a solid directly to a gas
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Equilibrium line
When losses from ablation are balanced by gains from the accumulation in a glacier
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Ice cover (general)
- Ice cover at the Pleistocene maximum was more than 3x greater than the present day
- Major ice extensions were over North America and Europe
- Ice extensions were over West and South of S. America
52
Ice cover (specific)
- The Antarctica and Greenland ice sheets only covered a slightly greater area than they do today. With the West Antarctica ice sheet expanding 10km either side of the peninsula
- The Laurentide and Cordilleran ice sheets covered East and West f North America stretching to around 3000km in width
- The Scandinavian Ice Sheet across Europe, in particular covering the area of the UK, widening to 500km
53
At present, ice covers over what percent of the Earth's land area? What percent of freshwater does this account to?
10%, accounting for 75% of the world's freshwater (about 1.8% of all water on Earth)
54
About what percent of all current glacier ice is contained in Antarctica?
85%
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Aspect
This can determine the amount of snow falling and where it settles. In the N. hemisphere, north and east facing slopes are both more sheltered and shadier
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What percent of the Earth experiences periglacial conditions?
20%
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Permafrost
Permanently frozen ground temperature below 0° for at least 2 years
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Factors affecting periglacial distribution
1. Climate
2. Proximity to water bodies
3. Aspect
4. Geology
5. Vegetation cover
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Blockfield
- Accumulation of angled, frost-shattered rocks on the ground
- Created by freeze-thaw weathering - water moves into rocks, freezes and expands by 10%, which causes them to shatter
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Solifluction/gelifluction lobe
- A tongue-shaped feature at the foot of a slop
- Created via solifluction - saturated (melted) active layer moves downwards under the influence of gravity
- Form on 10-20° slopes
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Stone Polygons
- On flat ground, stone polygons formed as the large stones settle around the edges of the domes; on slopes (30° or more), stone stripes formed as the stones move downhill
- Formed via frost heave - soil water freezes in a circular shape and expands by 10%, which pushes large stones to the surface
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Ice-wedge polygons
- Large-scale (5-30m wide) polygonal patterns on the ground surface
- Formed via ground contraction - the ground expands and contracts due to temperature changes, and forms cracks in the ground. These get larger as the cracks fill with water and freeze
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Pingo
- An ice-cored dome of topsoil, up to 70m high and 500m wide
- It melts in the summer, causing it to collapse
- Caused by groundwater freezing - a water lens freezes and expands, which shoves land upwards
- 2 types form - open (forms from groundwater under the surface) and closed (forms under a lake)
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Nivation hollows
- Rounded, formed in upland area
- Formed via nivation processes - a combination of processes weakens and erodes the ground beneath a snow patch
- These processes include freeze-thaw weathering, solifluction and meltwater environment(?)
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Loesse
- Extensive accumulations of wind-blown deposits
- Formed via aeolian action - absence of vegetation allows wind to transport large amounts of small sediments and redeposit it far from its source
- Can be over 300m high (e.g. North-West China)
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Braided stream
- Braided streams with multiple channels separated by islands of deposited material
- Formed via meltwater erosion - during short summers, thawing creates meltwater which erodes stream/river channels. Refreezing at winter causes a reduction in discharge and sediment deposition in the channel
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How has Arctic ice changed?
- Loss of summer sea ice in 2012
- At 3.4 million km², the minimum sea ice extend that year was 18% below previous record minimum in 2007
- 2012 - melting of the Greenland ice sheet
- Black carbon leads to increased surface warming - flaring of gas produced by oil extraction within the Arctic currently accounts for 42% of the region's black carbon emissions
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What are the impacts regarding the changes in Arctic ice?
- Affects marine and land ecosystems
- Ocean acidification - cold water can hold more CO₂ than warm water
- Due to retreating sea ice, increased exploitation of fossil fuels has occurred - e.g. exploiting the Barents sea region North or Norway and Russia
- Threatens biodiversity - walruses, polar bears, seals, etc.
- Consequences for global ocean circulation, weather patterns, visiting migratory species and greenhouse gas from thawing permafrost
- Rise of global sea levels due to thawing permafrost
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What developments have there been regarding the change in Arctic ice?
- 2013 - Arctic states signed a new, legally binding Agreement on Cooperation on Marine Pollution Preparedness and Response in the Arctic
- Commercial fisheries increased
- IMO developing the Polar Code - international code of safety for ships operating in polar waters
- Increased marine shipping - e.g. as of September 2013, the Northern sea route administration has issued 495 permits to navigate and operate along this route - this increased 4 fold compared to 2012
- In Russia, a new national park was opened called Beringia
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Continuous
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Discontinuous
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Sporadic
?
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James Ross Island casestudy
- Found in the NE Antarctic peninsula
- Has a cold, polar-continental climate
- Annual temperatures of -7°C
- Semi-arid climate = 200-500mm of precipitation per annum
- Marine terraces and raised beaches, scree
- Rock glaciers - common feature, located at the end of ice-cored moraines
- Solifluction lobes (medium to low gradient slopes)
- Major sediment sinks - alluvial fans and valley fills
- Freeze-thaw weathering - frost-shattered boulders, snow hollows, sorted stone polygons and stripes, and surface cracks
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Patriot Hills, Ellsworth Mountains casestudy
- 50km inland from the Ronne ice shelf grounding line
- 7 deglaciated valleys, 2 glacierised
- Dry, windy area, strong south katabatic winds
- Annual temperature = -28°
- Rock glacier-like landforms (flat topped , lobe-shaped, extend 400m downslope), debris slopes, rock falls
- Connected with ice-cored moraines
- Colder than James Ross Island
- Less developed periglacial landscapes due to a lack of meltwater
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Vestfold Hills, East Antarctica casestudy
- 200km² oasis
- 3rd largest ice-free area in Antarctica
- It has a cool, periglacial climate
- Annual temperature = -10.2°C
- Semi-arid environment
- Limited surface water available, as snow and ice melts from December to February
- Sink-filled valleys
- Low volumes of debris in glacier ice due to a lack of surficial sediments
- Meltwater rapidly redistributes sediments via mass movements and debris flow
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Terra Nova Bay, North Victoria Land casestudy
- Ice-marginal, high-latitude periglacial environment
- Cold, arid and windy conditions
- Limited freeze-thaw and solifluction due to lack of moisture and the shallow active layer
- Significant wind erosion leads to tafoni and honeycomb weathering
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Corrie/cwm/cirque
Armchair-shaped hollow with a steep backwall, e.g. Cwm Idwal, Snowdonia
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Formation of a corrie/cwm/cirque
1. Hollow forms in the ground (north-facing slope)
2. It fills with snow, which builds up to become ice - more erosion into hollow forms a nivation hollow
3. Freeze-thaw weathering weakens the rocks
4. Plucking - meltwater at the base of the glacier freezes into the rock. As the ice moves downhill, it plucks and removes rock from the bedrock
5. Abrasion - plucked rock fragments scratch and scrape the bedrock, and move the the rock lip (formed where ice thickness and erosion is reduced) via rotational movement (by basal slip)
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Randkluft
A crevasse (crack) between the glacier and the rock face of the cirque back wall, formed by radiation of heat from the rock
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Bergschrund
A crevasse within the cirque glacier formed by rotational ice movement
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Tarn
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Pyramidal peak
- A pointed mountain peak between 3 or more cirques
| - e.g. the Matterhorn, the Alps
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Glacial trough/U-shaped valley
- A steep sided, flat-floored straight valley
| - e.g. Mt Ffrancon Valley, Snowdonia (contains the ribbon lake: Llyn Ogwen)
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Roche Moutonnée
- Bare rock on the valley floor with a smooth stoss (upside valley) and a jagged lee (downside valley)
- e.g. Lembert Dome, Yosemite National Park, California
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Hanging valley
- Formed from small tributary v/u-shaped valleys high above the main glacial floor
- e.g. Pistyll Rhaeadar, Berwyn mountains, Wales
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Hanging valley
- Formed from small tributary v/u-shaped valleys high above the main glacial floor
- e.g. Pistyll Rhaeadar, Berwyn mountains, Wales
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Arête
- Sharp ridge between 2 retreating cirques
| - e.g. Striding Edge, Lake District
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