Glaciers Flashcards

Ice age meaning

An ice age is a long period of time when global temperatures fall and ice extends across the planet.

Glacier / interglacial periods

A glacial period is when the Earth is colder and lasts for 100, 000 years.

An interglacial is a warmer period of time that usually lasts for 10, 000 years.

Changes in the Earth’s orbit is the only thing powerful enough to cause this shift.

glacier, alpine glacier and ice sheet meaning, & how they form

A glacier is a mass of snow and ice. Alpine glaciers are those that form in the mountains and ice sheets cover huge areas of land.

They form when snow falls and does not melt. Snow that has not melted for at least a year is called firn. As the snow builds up in layers, the weight compresses it into ice. 

firn meaning

Snow that has not melted for at least a year

Glacial Regions Today

There are a number of glaciated regions left in the UK. Most of them are alpine glaciers but there are a couple of ice sheets.

1. Greenland Ice Sheet

2. Antarctic Ice Sheet

3. Himalayan Glaciers

4. Patagonian Ice Sheet

main features of a glacier

• The Zone of Accumulation

• The Zone of Ablation

• crevasses

• snout

• The Zone of Accumulation

where more snow falls then melts so the snow accumulates and builds up. This is usually higher up in the mountains where it is colder.

The Zone of Ablation

where more snow melts than falls so the glacier begins to retreat. This is usually further down the mountain where it is warmer or during summer months.

crevasses

Large cracks in the glaciers

snout meaning

The end of the glacier

Weathering meaning

the process of breaking down land in place

Freeze thaw weathering

when water seeps into cracks or joints in the rock and freezes. When water freezes, it expands and puts pressure on the rock. Eventually this breaks off and the rocks drop to the floor creating piles of material called scree.

How do Glaciers Erode?

• Plucking is when meltwater beneath the glacier freezes and bonds lose rock (often scree) into the base of the glacier. When the glacier moves, it takes this material with it. This is very effective in rocks that have joints or cracks that the water can seep into before freezing around the rock.

• Abrasion is also known as the ‘sandpaper’ effect. Rocks frozen into the base of the glacier scrape against the valley floor and sides and wear it away. They often leave scratches in the rock called striations.

How do Glaciers Move?

• Basal slip is when the glacier slides down the mountain under its own weight. There is often meltwater at the base of the glacier (due to either melting or compression melting) which helps the glacier to slide. 

• If the movement is more curved over dips and hollows in the mountain, it is called rotational slip

• If the glacier is frozen solid to the ground which is often during winter, gravity pulls the glacier downhill but instead of sliding, it behaves like a plastic. This is called internal deformation.

Glaciers can also retreat or advance depending on whether they are growing in size or melting. This is called mass balance. If accumulation is greater than ablation, the glacier will advance down the mountain. If ablation is greater than accumulation, the glacier will melt and retreat up the mountain

How do Glaciers Transport Material?

As the glacier moves downhill, it pushes loose rock and material in front of it in a process known as bulldozing.

What causes deposition?

Deposition is when material is dropped as the ice melts.

Deposited material is called glacial till. This is often deposited as a glacier retreats. 

Ahead of the glacier, meltwater will carry finer material further from the snout of the glacier creating an outwash plain. This material is sorted; the large material is deposited closer to the glacier and the finer material is transported a further distance

Moraine - landforms formed by the deposition of the glacial till

Corries meaning

Corries are large hollowed out depressions (almost like an armchair) on the upper slopes of a mountain.

They have a steep back and a raised ‘lip’ at the front. A corrie may contain a lake called a tarn.

Formation of corries (Erosional)

1. Snow accumulates in the sheltered hollow on a hillside. It does not melt in the summer as it is high up the mountain and sheltered.

2. Freeze-thaw weathering and slumping enlarges the hollow and forms scree within the hollow

3. The snow turns into ice and a small corrie glacier is formed

4. The glacier moves through rotational slip and abrades the hollow making it deeper.

5. Plucking makes the back wall of the corrie steeper.

6. There is reduced erosion at the front of the corrie due to the ice being thinner and less erosion forming a raised lip.

7. Sometimes moraine can be deposited at the lip

8. A tarn is a corrie lake that may form in the bottom of a corrie

e.g. Red Tarn in the Lake District

Formation of aretes and Pyramidal Peaks (erosional)

If two corries form back to back, it creates a high, narrow ridge called an arete that separates the two corries.

If three or more corries form, there may be a single peak called a pyramidal peak.

What landforms form in glacial valleys?

• Glacial Trough

• Truncated Spurs

• Hanging Valleys

• Ribbon Lakes

Glacial Trough

When a glacier moves through a V-shaped valley, abrasion and plucking deepens and widens it. This creates a wide valley with a flat bottom and steep sides.

• Truncated Spurs

Interlocking spurs are when ridges of hard material jut out into the valley or the path of a river. Glaciers erode through these, cutting them off halfway up the valley sides. This leaves a rounded piece of land at the edge of the valley.

Hanging Valleys

Smaller tributary valleys may have had smaller glaciers forming in them. They were unable to erode down to the same level as the main glacier and are left hanging over the main valley.

Today, these often have waterfalls.

Ribbon lakes

These are long, narrow lakes resulting from glacial erosion of the trough.

Softer rock on the valley floor is deepened further than harder rock.

 Water fills these deeper areas.

moraine meaning (depositional)

Any material transported by a glacier is called moraine.

This can be carried beneath the glacier, within in or on top of it.

When a glacier reduced in size, material it is carrying is deposited.

Terminal moraine

Material deposited at the end (snout) of the glacier

Lateral moraine

Material deposited along the sides of the glacier. This is usually made up of weathered material that has fallen from the sides of the valley

Medial moraine

Material deposited in the middle of a glacier. This is formed from two lateral moraines merging together where two glaciers meet

Ground moraine

This is material that is deposited across the ground as a glacier retreats

Recessional moraine

These run parallel to terminal moraines and they mark the different positions of the glacier as it retreats

glacial till meaning

Once material is deposited, it is called glacial till or boulder clay which is made from a mixture of different sized sediment. 

Drumlins (depositional)

This is an egg shaped hill formed from the deposition of moraine. 

A boulder or rock (obstacle) is in the path of the glacier. Material (that is transported beneath the glacier) known as ground moraine is deposited around this.

As the glacier moves over, the pressure shapes the material into the typical egg shaped hill of a drumlin.

The gentle sloping lee end points to the direction of ice movement.

Erratics meaning (depositional)

These are rocks that have been deposited by a glacier.

They are usually made of a rock type that is not usually found in that area.

They have been transported by the glacier from one area and deposited in another.

Meltwater meaning

As the glacier melts, water carries finer material (glacial till) further away from the glacier where it is deposited creating an outwash plain.

Compared to moraine, this material is sorted according to size with larger material deposited closer to the glacier and finer material carried further.

Central Lake District

The Central Lake District has mountains and ridges cut by wide, steep-sided ‘U' shaped valleys often occupied by ribbon lakes such as Windemere.  

Helvellyn is one of the UK’s tallest mountains standing at 949m above sea level and made from tough igneous rocks. There are many corries and aretes. Striding Edge is a famous arete that forms the back wall of Red Tarn Corrie.

Langdale is a spectacular U shaped valley, with large lateral moraines running up the sides.

The Easedale valley has a number of moraine features including recessional and ground moraines.  Further South East, the area around Kendal has some spectacular drumlins.  Kendal Castle is actually built on top of a drumlin!

There is a hanging valley at Grisedale.

Fields in Borrowdale actually use the terminal moraines as natural boundaries.

Farming in glacial landscapes

Farming crops is difficult due to

• Steep slopes are not accessible to machinery

• Thin, infertile soils

• Heavy relief rainfall leading to soil erosion and flooding

• Cold temperatures results in a short growing season

It is possible for animal grazing in the area. Sheep were introduced to the Scottish Highlands in the 1800 due to demand for wool from the textile industry. More recently there has been deer for venison and cattle for beef. In the summer they are able to graze highland areas and in the winter they are kept in farms on the valley floor. In the Lake District, the Herdwick Sheep are the most common.

The valley floor is sometimes more suitable for farming due to the flatter land, less extreme climate and the large glacial deposits creating more fertile soils. This can be used for growing cereal, grass for hay and potatoes. The only issue is the land here is limited compared to more open farms in other rural areas.

Forestry in glacial landscapes

2 million hectares of forests in the UK are coniferous, many of them in upland areas. They can cope with the acidic soil.

Some of these occur naturally or have otherwise been planted. 

The Forestry Commission was created in 1919 to ensure this was managed properly so there was always a supply of timber. In the 1980s, forest cover increased due to private investors.

Wood is used for timber for furniture and building construction and to make wood chips for gardens and biofuel. It is also perfect for creating paper. 

Grizedale Forest in the Lake District near Windermere has planted a large expanse of Sitka Spruce trees and are used for timber.

Tourism in glacial landscapes

In upland areas, tourism employs more people than any other industry and is one of the most important sources of income.

Glaciated landscapes attract mountain climbers, cyclists and walkers as well as those more interested in pretty scenery and culture.  Not only this, there can often be skiing, wildlife photography and water sports.  

The Lake District is very popular as it has a mild climate and is easily accessible. In 2023, tourism in the Lake District generated £2.3billion, attracted 18 million tourists and created approximately 19, 000 jobs.

Quarrying in glacial landscapes

Geology of upland areas is very unique as they are composed of tough, resistant rocks that are not found in lowland areas. These are suitable for construction materials. The gravel deposited by meltwater in lowland areas is also used for building materials.

It also created employment either directly or indirectly in the area.

A lack of population also means there are fewer objections to quarrying when explosives are used.

Despite this, there are still many concerns over wildlife disruption, landscape scarring, water pollution and traffic congestion.

Honister slate mine in the Lake District not only quarries slate but now offers tourist opportunities into the history and importance of slate quarrying in the area.

Land use meaning

Land use is how the land is used for a specific type of activity.

Conflicts about land use can occur when…

there is a disagreement on how the land should be used. This is often between different stakeholders (people with an opinion or affected by the activity.

There is often conflict between economic activity and conservation (preserving the natural environment).

Farming potential conflicts

Farming can result in the clearing of trees in an area which increases flood risk and soil erosion.

Over grazing of animals can actually result in a loss of vegetation which results in soil erosion which causes water pollution.

conflict with conservationists

There is ongoing conflict in Swindale Valley where the RSPB has imposed a limit on the number of sheep to allow habitats to replenish

Potential solutions:

• Farmers can plan to rotate sheep around different areas on a rota

• Use less pesticides and fertilisers

Forestry potential conflicts