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Glaciated Landscapes

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Glaciated Landscapes

Glaciated landscapes are formed by a combination of erosional, fluvioglacial, and depositional glacial processes. The resulting feature may be an active glaciated landscape, which means a glacier is currently present. It could also be a relict landscape, and although it no longer contains an active glacier, it still has distinct features left behind by its glacial past.

Glaciated Landscapes Glacier StudySmarterA glacier calving in Alaska, USA, Pixabay

Glacial landscapes contain both large- and small-scale features. These are unique to glaciated landscapes and can help us understand the characteristics, history, and mechanisms of glacial systems.

Active glaciated landscapes

An active glaciated landscape is where the glacier is present.

A glacier is a huge mass of ice (usually found in highlands), and it generally falls into two broad categories: alpine glaciers and ice sheets. Both types of glaciers broadly form in the same way. Over many years, the accumulation of snowfall exceeds the rates of ablation. The long-term net positive accumulation of snow causes it to compact as a result of high pressure on its base layers, which is caused by the weight of the upper layers of snow. Compaction occurs when the pressure on the ice forces air out of the snow layers.

When enough air is pushed out, meaning that air makes up 50% of the volume between the snow crystals, the snow forms into granular ice. The next stages of compaction lead to the formation of firn (approximately 25% air), followed by glacial ice (approximately 20% air). The reduction of air between the snow/ice crystals increases the density of the materials, causing the change from snow to granular ice to firn to glacial ice.

What is the difference between a glacier and an ice sheet?

The difference between alpine glaciers and ice sheets relates to the locations in which they form and their directions of travel.

Alpine glaciers

Alpine glaciers form on mountainsides, usually within a corrie (also known as a cirque). When they escape these hollows, they traverse down valleys. The accumulation of ice follows the same pattern mentioned above.

After a long period of accumulation and compaction, an increase in pressure in the body of ice may cause the development of meltwater in its base. Alongside the shape of the hollow and the weight of the ice mass, the lubrication caused by the meltwater sets off a process called rotational slip. The glacier begins moving in a circular motion. Due to this motion, there is a chance of the glacier escaping the corrie/cirque hollow. It would then start traversing down the valley in which it is located.

This process is discussed in depth in Erosional Landforms.

Ice sheets

Ice sheets are not limited to mountainsides or valleys. Unlike alpine glaciers, they do not necessarily form within hollows but rather anywhere with high accumulation potential. As the accumulation of snow is not bound by any landscape, ice sheets generally begin as broad domes spreading out in all directions. As the sheet begins to move, it will cover the environment in a large blanket of ice. At their largest extent, these sheets are known as continental glaciers.

Examples of continental glaciers include Greenland and the Antarctic Ice Sheet.

What is a glacial system?

A glacial system consists of the inputs, transfers, stores, and outputs that form a glaciated landscape.

By exploring these features and how they relate to one another, we can understand the underlying reasons why glaciated landscapes function the way they do and how their landforms form the landscape as a whole.

Inputs

Inputs are the physical matter that enters the glacial landscape. In glacial systems, these are usually snow, ice, and rain, which enter through precipitation

These inputs may also enter via avalanches or by wind blowing them in from other landscapes.

Transfers

Transfers describe the movement of the components of a glacial system (the largest of which is the ice mass itself).

An example is the movement of the ice mass due to gravity and the landscape’s gradient, which is accelerated by an increase in accumulation at the source of the glacier. This process of transportation is largely behind glacial effects on the landscape.

The glacier's movement erodes the valley in which it resides by a mixture of quarrying, abrasion, and fluvioglacial erosion. These will change V-shaped valleys into U-shaped valleys and form distinct landscapes such as drumlin fields, moraines, etc. This is discussed further in Glacial Landforms.

Stores

The mass of ice within the glacier is the main store of the system.

This store will vary in size according to the number of inputs, also known as accumulation, and the number of outputs, also known as ablation. Meltwater may also be considered as a store when connected to the glacial mass, for example, supraglacial lakes or perhaps subglacial streams.

Outputs

The primary output from a glacial system is the loss of water vapour from the surface, often via sublimation.

A more large-scale output is ice calving. This occurs when the part of a glacier that moves out into a body of water breaks off from its snout. It may also occur when a glacier hangs off a valley’s edge, but this is not as common.

How is a glaciated landscape formed?

Glaciers begin forming in areas where snow can accumulate at a greater rate than it melts. Soon after falling, the snow compresses under pressure and becomes denser and more tightly packed. It changes from light crystals to hard, round ice. This process repeats until the snow is compacted into glacial firn, which is a process known as firnification.

Following a long process of firnification, the ice will thicken and accumulate a large mass. This large mass of ice begins to move under its own weight and exerts a significant amount of pressure, causing the firn to melt despite a lack of increase in temperature. The increased meltwater decreases the friction between the base and the ice mass, allowing the ice to escape the hollow in which it has formed. This accumulated body of ice is known as a glacier.

Gravity pulls the glacier down and allows it to advance. As it does so, the numerous processes that shape a glacial landscape occur and begin shaping the landscape.

Over the course of many years, a distinct glacial landscape will form as a result of these glacial processes. Even if a glacier fully retreats and is no longer present, the landscape is permanently changed.

Some examples of glaciated landscapes

The Mer De Glac glacier, located on the northern slopes of the Mont Blanc Massif in the French Alps, is an example of an active glaciated landscape. The Mer De Glac is continuously retreating as a result of increasing temperatures in Europe, attributed mainly to global warming. Active glacial landscapes are very important because they help us understand the landforms we see in relic glacial landscapes.

An example of a relict glacial landscape is the Lake District, located in Cumbria in northern England. This area is characterised by numerous post-glacial landforms such as drumlins in the Vale of Eden, glacial lakes known locally as tarns, and ribbon lakes such as Lake Windermere.

Glaciated Landscapes Innominate Tarn in Cumbria StudySmarterInnominate Tarn in the Lake District, UK, Pixabay

Many of these post-glacial landscapes, especially ribbon lakes and tarns, serve as tourist attractions. Millions of visitors come to the Lake District each year.

Glaciated Landscapes - Key takeaways

  • Glaciated landscapes have distinct features formed by several erosional, depositional, and fluvioglacial processes.

  • Glaciers are large masses of ice formed by compaction.

  • There are two types of glaciers, namely alpine and ice sheets. The type of glacier depends on the environment in which it was formed.

  • There are two forms of glacial landscapes: active and relic glacial landscapes.

  • Glaciers form as a result of the accumulation of snow leading to firnification.

  • A glacial system consists of inputs, outputs, stores, and transfers.

Frequently Asked Questions about Glaciated Landscapes

Glaciated landscapes are formed by erosional, fluvioglacial, and depositional processes that are caused as a direct result of the presence of the glacier.

Glaciation comes with many processes that directly affect a landscape. Erosional processes wear down the landscape, depositional processes leave behind distinct glacial features, and fluvioglacial processes do both. Once glaciation takes place, the landscape is permanently changed.

These are some effects of landscape changes: Glaciated landscapes are often used by people for economic activities. They provide easy access for quarrying. The landforms also attract tourists, which brings revenue to the local economy. Glaciated landscapes, such as the Lake District in the UK, are also ideal for pastoral farming.

Glaciers are important because glaciers such as the Mer De Glac are indicators of global warming and climate change. They also give rise to significant economic opportunities, for example in the Lake District in the UK.

Final Glaciated Landscapes Quiz

Question

Define Icehouse Earth and Greenhouse Earth.

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Icehouse Earth is when there are large ice masses present. No or minimal ice masses are present in Greenhouse Earth.

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Define stadial and interstadial.


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Stadials are short-term periods of ice advance, whereas interstadials are short-term periods of ice retreat.

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Summarise the difference between ice extent in the Pleistocene Epoch and the current day.


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Ice cover during the Pleistocene Epoch was three times higher than the present day. 

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Name two depositional landforms that are evidence of the Pleistocene Epoch in the UK.


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Drumlins and erratics.

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Name two erosional landforms that are evidence of the Pleistocene Epoch in the UK.


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Roches moutonnées and glacial troughs.

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What is the effect that is increased when there is an increased presence of surface ice?


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The albedo effect.

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Name an example of climate change affecting a glacial period.


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The multiple glacial and interglacial cycles during the Pleistocene Epoch.

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What caused the glacial/interglacial as well as the stadial/interstadial cycles during the Pleistocene Epoch?


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 Combinations of long- and short-term climate change causes.

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Processes that form glaciated landscapes are:

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Erosional, depositional, and fluvioglacial.

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You are in a U-shaped valley in a country without glaciers. What type of glaciated landscape are you looking at?

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Relict landscape.

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What two processes contribute to the formation of a glacier?


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Accumulation and firnification.

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Name three economic uses of a relic glacial landscape?


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Farming, tourism, and quarrying.

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Greenland is mostly covered by a(n) _______ glacier.

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Continental

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An ice sheet forms on the side of a mountain peak.

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False.

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Another term for  'corrie' is _______.

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Cirque

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Name an example of a continental ice sheet?


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The Antarctic ice sheet.

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Mont Blanc is a(n) _______ glaciated landscape whereas the Lake District is a(n) _______ glaciated landscape.

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Active; relict.

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What input processes can cause the accumulation of ice mass?

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Snow, precipitation, and avalanching

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Why do we call the glacial equilibrium dynamic?

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Because the equilibrium line shifts according to the ratio of accumulation and ablation

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What are the states of a glacial system?


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Positive and Negative Mass Balances.

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What happens if accumulation exceeds ablation?


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Glacier advances

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What happens if ablation exceeds accumulation?


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Glacier retreats.

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What is the equilibrium line?

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The point at which the accumulation and ablation is more or less equal

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What is ablation?


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The processes by which mass exits the glacial system.

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What is accumulation?


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The processes by which mass enters the glacial system.

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Name 2 ablation processes?


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Ice calving, Run-off

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Name 2 accumulation processes?


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Precipitation, Wind

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Give an example of significant ice calving

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Greenland where ice calving can be responsible for up to 15,000 glaciers a year

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What is generally the primary input source for glacial mass?


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Precipitation

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What determines the type of glacial terminus?


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Whether the glacier terminates due to a body of water or due to reaching a low enough altitude on dry land.

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What does supraglacial mean?


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On top of a glacier.

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What is the upper bound of sublimation as a percentage of total ablation?


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100%

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Name a glacier where sublimation accounts for most ablation


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The Taylor Glacier

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Name a glacier where sublimation accounts for most ablation

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The Taylor Glacier

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Is avalanching a significant accumulation process?


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In some instances, it is suggested that it may be the dominant process, however, this is not the case in all glaciers and further research is needed to confirm the findings which suggest that avalanching may make up the majority of the accumulative processes on particular glaciers.

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What is finification?


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The process of constant layering of snow that eventually causes the formation of firn.

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What is ice calving?


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When a significant mass of ice is detached from its glacier or ice sheet.

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Is wind considered a significant contributor to glacial accumulation?


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It is not. 

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 What is sublimation in the context of glacial accumulation/ablation? 


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The state change from a solid to a gas, in the context of a glacial system this contributes to ablation.

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Which process/es cause movement in cold-based glaciers?

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Internal Deformation

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How is extensional/compressional flow linked to problems with reconstructing past ice mass extent?

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 It can cause variations in the height of the trimline which reduces the possibility of determining the precise height of the glacier.

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Where do Polythermal glaciers occur?


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Lower-climate zones e.g. Svalbard, Norway.

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What two aspects of lithology affect glacial movement?


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Permeability as well as the hardness

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Which processes cause movement in warm-based / temperate glaciers?


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Basal Slippage: Enhanced basal and regelation creep, Extensional Compressional Flow and Surges; Internal Deformation too.

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What percentage of movement can Basal slippage account for in Warm-based glaciers?


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75%

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What is the approximate general speed of internal deformation?

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1-2cm a day

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What speed increase and total forward motion of a glacier can surge account for?


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Speed increase: 100x, forward motion: 90%

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Name an example glacier where compressional/extensional flow can be observed in the present day


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Mer De Glac

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Name 3 factors that control glacial movement

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3 of (Lithology, Altitude, Gravity, Ice temperatures, Mas Balance, Ice thickness)

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How does the permeability of the subglacial surface affect glacial movement?


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Impermeable surfaces trap meltwater which decreases friction allowing for faster glacial movement, permeable surfaces allow meltwater to escape so there is no lubrication effect and the glacier has no increase in speed or movement.

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