How does Glaciers affect the Landscape?

Glacial Processes

After studying What and Where Glaciers are, I am now going to look at how Glaciers shape and affect the landscape around them, this process is know as 'Glaciation'. With the weight of Glaciers and the gradual movement means that Glaciers can drastically change the land and cause new and unique landforms.
The Three processes by which glaciation affects the landscape is erosion, transportation and deposition.

Erosion

WEATHERING:- The most common form of erosion that Glacier's cause on the landscape if Freeze-thaw weathering. This is the action of glacial water getting into cracks,holes and joints within the rock, when it freezes it causes the rock to expand and widen. When the temperature heats up, it causes the water the melt and the rock contracts. Eventually this process cause pieces of rock to break off.

PLUCKING:- Plucking occurs when loosened fragments of stones and rocks, become frozen to the ice. When the Glacier moves, the stones are literally plucked from the ground, it leaves behind a jagged landscape.

ABRASION:- At school I always remembered this as the sand paper effect and in term of Glaciers its no different. Stones and rocks are embedded into the Glacier and as the Glacier moves the rocks rubbed against the bedrock and wears it down. It produces polished bedrock surfaces, that has scratches on.

There is more erosion processes that occur within Glaciation, however I have highlighted the most predominant processes.

On the BBC bitesize revision pages, I found this clip that I thought simply explained what a Glacier is but erosion processes as well. Please click on link below to watch.

http://www.bbc.co.uk/learningzone/clips/3079.bb.wmv.

 



Transportation

Glaciers are capable of moving large quantities of rock fragments and soil debris across huge distances. The distances all depends on material and the speed of movement of the Glacier. It is also important to put out here that Glaciers do not just move deposits from erosion, it may come from external sources such as:-

• Rockfalls from weathering off other slopes
• Avalanches
• Wind-blown materials, such as ash and dust.

Deposition

The intense erosive actions produces large amount of sediment that can be transported by the movement of the Glacier. The deposition of sediment can be laid down miles away from their origins.

The collective name for all the sediments and debris deposited under all glacial conditions is Glacial Drift.

However Geographers have classified glacial sediment according to its mode of deposition:-

Fluvio-glacial - Sediments that were deposited by melting ice or by glacial streams, meltwater is abundant in warm based Glaciers.

Glacier Till - This is when debris is deposited directly by the Glacial, dropped 'in situ' by retreating ice. 

The below diagram shows the classifications of sediments in deposition.



http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchambers/GeoBytes/AS%20A2/A2/Glaciation.Web/glacial_deposition.htm



The When and The Why?

When did the Glaciers Occur?

The WHEN question is one of the 5Wquestions that I have set out for myself to answer. However doing my research. I have realised that this is a toughie, as there is no answer for this.

As previously stated Glaciers currently cover 10% of the world's land surface, however this Glacier Ice has been on the land surface for hundreds of years and it is only being sustained by annual precipitation.
Majority of the Glaciers that is currently around may have originated from the Last Ice Age, when Glaciers covered 32% of the land area. As the world has warmed up, the Ice has been melting. (this issue will be looked at in a later post), this is when Isostatic adjustment occurs. As the pressure is released from the shrinking Ice, the land is rising, as the pressure from the original Ice pushed the land surface down.



Why Do Glaciers Form

I have actually answered this question in my section of  'What is a Glacier', however I am going to go through it again. As repetition can sometimes be a goo thing.

When snow falls over hundred years and the climate of the area allows the snow to settle without melting or evaporating the snow. The pressure of the snow compresses together and forms a large Ice mass.

When Glacier Ice appears blue, it means that the ice is very dense. Years of compression makes the ice denser, as it pushes out any air pockets between the ice crystals. This dense ice does absorb all the colours of the spectrum but it primarily reflects Blue as there are very little air pockets.