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Shaping of the Earths Surface

All across the world it oblivious that in the past there has been a huge amount of shaping of the earths surface to form the beautiful landscapes and landforms we can witness today. The last Ice Age played an enormous part in the sculpturing and transformation to our planet which was estimated to take place over 20,000 years ago. (url 1). In Britain at the height of the glacial period, ice sheets stretched as far South as Kent and the region of arctic tundra stretched far into Europe. (URL 2) Once the ice sheets covered the UK it was then it put an influential stamp on the landscape with a number of processes occurring to allow the change in the earth's formation to arise.

In many places in Britain and across the world there is a huge amount of landscapes and landforms. The table below identifies the features produced by glacial erosion. It gives an illustrated description of the feature and the formation as well as giving most common examples. (Ref 1)

Erosional feature

Formation & or Description

Example

Pyramidal Peak

Steeped long in profile in a glacial trough (valley). Resistant rock only remains after ice-direction-facing side and plucking on the lee.

Machhappuchare, Nepal. (Ref 2)

Glaciated Valley

Normally U-Shaped valleys, glacial trough - its floor being above sea level.

Great Langdale

valley .(url 3)

Fjord

Same as a Glaciated valley. Many are deep; it is assumed that glaciers that were formed in these valleys were so heavy - eroded the bottoms of the valleys far below sea level. After the glaciers melted, the waters of the sea invaded the valleys.

Hardangerfjord in

Hordaland, Norway.

(url 4)

Hanging Valley

Floor sits above a trunk valley and is form tributary valley.

Sour Milk Gill

Grasmere (url 4)

Striations

Scratches on bedrock.

Central Park,

New York (Ref 2)

Cirque

Pointed peak with Radiating arêtes. Debris either subglacial or englacial dragged over exposed rock.

Central Pyrenees, in the Pyrenees National Park (Ref 2)

Arête

Tributary Glacier left high above the main valley. Formed form extending and compressing flow over deepens parts of valley floor.

Helvellyn (Url 8)

Truncated spur

Circular lake which is small yet deep. Is formed due to two cirques cutting backwards into each other.

Glen Dee, in

Cairngorms (url 5)

Ribbon lake

Steep, cliff-like valley sides

Windermere in the Lake District (url 4)

Cirque Lake

Narrow, Knife-edge ridge, weight of the valley glacier deepens and widens it.

In west Wales (Ref2)

Roche moutonnée

Rocks scarred with thin parallel scratches

Glacier Bay, Alaska. (url 6)

The main processes that are associated with glacial erosion are: frost shattering, rotational movement, abrasion, plucking, and extending and compressing flow. Frost shattering is the process that forms lateral moraine; the process produces a high volume of loose material which fall from the valley sides onto the edges of the glacier. The main attribute to this process is the expansion of freezing water captured in cracks, is generally independent of the water-to-ice expansion. This same phenomenon occurs within pore spaces of rocks. They grow larger as they attract liquid water from the surrounding pores. The ice crystal growth weakens the rocks which, in time, break up. The phenomenon is caused by the almost unique property of water in having its greatest density at 4 C, so ice is of greater volume than water at the temperature below 4 C. When water freezes, then it expands and puts its surroundings under intense stress. Freeze induced weathering action occurs mainly in environments where there is a lot of moisture, and temperatures frequently fluctuate above and below freezing point. A great local example of where frost shattering is Honister Pass in the Lake District National Park where the formation of screes (rock fragments broken off by the process freeze thaw) can be found, often in alpine and periglacial areas which is referenced later. Also freeze-thaw takes an important role in the formation of a Cirque/ Corrie for example north eastern side of Helvellyn in the Lake District. (Url 8)

Abrasion is what is classically known as the sandpapering effect of angular material. Plucked debris in basal ice grinds into the bedrock, just like sandpaper across wood. This grinding leaves long groove in the bedrock called striations (if the sandpaper or ripper is coarse) or smooth polish (if the sandpaper is fine or the bulldozer is pulling a smoothing implement). If the glacier is no longer present, striations can be used to determine the direction of ice flow. Abrasion can also be seen through the presence ofchatter marks, acute pressure fractures. Abrasion,too, requires a "warm" glacier bed. A great example of abrasion where striations can be seen is in Church Back Coppermine's Valley, Coniston, and Central Park in New York. Also the truncated spurs that is present in West Water. (Ref 2)

Plucking (or quarrying) is the process that exploits pre-existing fractures in the bedrock. For example, the glacially plucked granitic bedrock near Mariehamn, Aland Islands. There are two main types of glacial erosion, the first one of which is plucking (analogous to a backhoe). As a glacier flows down hill there may be an obstruction which causes a high-pressure zone to form on the up-ice side and a low-pressure zone to form on the down-ice side. If the glacier is at the pressure melting point, basal ice melts in the high-pressure area and the resulting water infiltrates cracks present in the bedrock. Once this water has seeped through the bedrock and into the low- pressure area the water can refreeze. This frost actionleads to the dislodging of rock fragments from the bed. This loose debris can also refreeze to the basal ice and be transported with glacier flow. Plucking, to be effective, requires a warm-based glacier. (Url 9)

Rotational Movement is the downhill movement of ice which, like a landslide, pivots about the point. The increase in pressure is responsible for the over deepening of a cirque floor. And extending and compression flow, explains where maximum erosion will occur in conditions that fluctuate around 0 degrees and where jointed rocks are this allows free-thaw and frost shattering to occur also where ice increases in height where it be due to the valley narrowing or two tributary glaciers joining. This mainly occurs in conditions of temperate latitudes, which allows velocity of the glacier to increase due to the lubrication of the meltwater.

Features formed by glacial Deposition:

Feature

Description and Formation

Eaxmple

Till

Meltwater along valley sides of, delta at the ice front, deposits mound of sorted material i.e. till. When the ices englacial material is too heavy to be carried with the ice.

Norway (url 4)

Terminal

moraine

Rock thats carried from the source to a different area of rock. It is small, shallow lake containing stratified material.

Waterville Plateau of the Columbia Plateau in Washington. (Ref 2)

Recessional

moraine

It is the gathering of two lateral moraines. It is spread over lowlands and material is sorted often gravel, sand and clay.

Lateral moraine

Where meltwater makes connection with ice of glacier sorted material is there deposited.

Above Lake Louise, Alberta, Canada. (url 4)

Medial moraines

In low-lying area meltwater reduces in velocity and unsorted, angular gravel is deposited, followed by sands and clays.

Gulkana Glacier, Alaska (Ref 2)

Push moraines

Unsorted material across the valley is deposited during a standstill in the ice retreat.

Spitsbergen (Ref 2)

Drumlins

Deposited by subglacial streams unsorted material found alongside glacier/ valley.

Clew Bay, County Mayo (URL 7)

Erratic

Majority of material is unsorted subglacial materials, narrow ridges extending across valleys.

Ingleborough in the Yorkshire Dales. (Ref 2)

Kettles

Material such as boulders found in the centre of glacier, at the advance of the ice.

Isunngua highland, central-western Greenland. (Ref 2)

Esker

Material deposits push upwards from valley floor through temporary ice re-advances. Rocks are not native to area.

Sims Corner National Natural Landmark, Washington, USA. (Ref 2)

Kame

After melting ice sheets, blocks are detached, later surrounded by fluvioglacial material.

Waterville Plateau of the Columbia Plateau in Washington. (Ref 2)

Outwash plain

Unsorted, angular material found alongside valley mainly resulting from frost shattering.

Kankakee (River) (url 4)

The Yorkshire Dales is an excellent example to show so of these features and how they are formed. The area consists of three Jurassic rock layers (lower 200 million years' old, middle and upper 150 years old) the area was bordered to the North, East and West by ice sheets often hundreds of metres thick. The area still bears hallmarks of this time, the most dramatic of these being the great overflow channels where glacial lakes and meltwater broke through low points in the landscape to carve deep and steep sided valleys such as Newton Dale and Forge Valley. In Sutton Bank there is an escarpment that runs all the way from here to the coast at Scarborough. The depression that lay between the upland areas of the North York Moors and the Pennines. As it scraped along the western edge of the moors, the tremendous force of the ice gouged out the soft underlying rocks, causing the hard tops to tumble down. The result was a near-vertical escarpment, of the type usually seen at the coast. As the ice melted it left layers of mud along the bottom edge of the cliff, in what are known as lateral moraines. These mud deposits blocked up normal drainage channels causing small lakes to form Gormire Lake, below Sutton Bank, is the last remaining glacial lake. Broad u-shape valley with gently undulating or flat valley floor and gently terraced valley sides valley overlying sandstones and slates of the ingletonian series, narrowing both at it northern and around Horton in Ribblesdale and to the south of Helwith Bridge.

Elsewhere across the North York Moors and Howardian Hills the features left by glacial meltwater erosion are more imposing and widespread. Most notably, the meltwater cut channels of Newtondale and Kirkham Gorge represent the greatest influences of glacially associated waters. There are few significant meltwater features within the LP area. However, both Newtondale and Kirkham Gorge are associated with proglacial Lake Pickering which does extend into the south east of the area.

Periglacial processes which operate and the landforms in which are developed in periglacial areas.

Feature

Processes

Landforms

Ground Ice

Ice crystals and lenses (frost-heave)

Ground contraction

Freezing of ground water

Sorted stone polygons

Ice wedged, unsorted polygons

Pingos

Frost weathering

Frost shattering

Blockfields, talus, tors

Snow

Nivation

Hallows

Meltwater

Solifluction

Streams

Rock streams

Braiding, dry valleys in chalk

Wind

Windblown

Loess

Periglacial

The Quaternary period brought successions of colder climate resulting in both glacial and periglacial conditions. The Devensian period was the final glaciations of the quaternary beginning some seventy thousand years ago and ending thirteen thousand years ago. During this final glaciations ice encroached from the west, north and east. As the harder rocks deflected the south-moving ice to the north and west the evidence of glaciations is revealed only in the carving of the steep western facing slopes and the deposition of glacial materials.

In the Vale of Pickering an ice-marginal lake was formed from water supplied by the Newton Dale meltwater channel as it drained the north lying upland areas. The lake was responsible for a substantial deposition of lacustrine material which today creates the flat fertile vale landscape. The lake was dammed by North Sea ice to the east and eventually formed an overflow channel to the south-west creating the gorge at Kirkham. Against the escarpment edge are lateral moraines - material derived from frost shattering carried along the edge of glaciers and deposited as banks of material following periods of ice recession.

The effects of glaciation have rendered the LP area a truly distinctive landscape cutting the escarpment edge, producing meltwater channel features and well drained upland plateaus. Glacial processes have also been responsible for drift deposits.

Fluvioglacial Landforms

Fluvioglacial landforms are moulded by glacial meltwater and have, in the past been considered to be mainly depositional. However more recently it has been acknowledged that meltwater has a huge role in particular in temperate glaciers in creating erosion features. Most meltwater is plagiaristic to abrasion. In summer when the ice begins to get warmer the water gets an increase in velocity which makes it much more turbulent allowing it to transport larger amount of materials. These larger materials through abrasion and partly solution can create subglacial valleys and large potholes. When there is a decrease in discharge deposition is most often will occur.

References

Books

Ref 1: Fundamentals of geomorphology: Richard John Huggett page 218-219

Ref 2: Geography 'an integrated approach' David Waugh page 102

Ref 3: Glaciers and landscape: David E. Sugden and Brian S. John page

Ref 4: Global Geomorphology: Summerfield page

Websites

URL 1: http://www.ace.mmu.ac.uk/eae/Climate_Change/Older/Ice_Ages.html

URL 2: http://www.slideshare.net/RCha/glacial-deposition-a2

URL3: http://www.bbc.co.uk/schools/gcsebitesize/audio/geography/pdf/formation_of_a_glacial_trough.pdf

URL 4: http://en.wikipedia.org/wiki/Fjord

URL 5: http://www.fettes.com/Cairngorms/truncated%20spur.htm

URL 6: http://geology.about.com/library/bl/images/blrochemout.htm

URL 7: http://www.geography-site.co.uk/pages/physical/glaciers/drum.html

URL 8: http://www.geography-site.co.uk/pages/physical/glaciers/corrie.html

http://www.bbc.co.uk/schools/gcsebitesize/audio/geography/pdf/formation_of_a_glacial_trough.pdf