• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Distinguish between abrasion and plucking

Extracts from this document...

Introduction

6a) Distinguish between the glacial erosion processes of abrasion and plucking. Plucking occurs high on the glacier, well into the zone of accumulation, because for plucking to occur the temperatures have to have slight fluctuations around the melting point of the ice. Plucking occurs usually at the bottom of the glacier where, because of the pressure pushing down on the ice from above, the ice is at the pressure melting point. When there is a rock with a crack in it, the melted ice fills the crack and then refreezes. The refreezing exerts a pressure on the rock and weakens it but the water also freezes to the bottom of the glacier and is pulled away. When the frozen water in the crack is pulled away so is the rock. Abrasion however can occur anywhere along the profile of the glacier. Abrasion is the sandpapering of material. Debris can be put into the glacier by many methods including plucking and the material is then dragged along the bed of the glacier. ...read more.

Middle

But the amount of debris also varies along the profile of the glacier. As at the top of the glacier in the zone of accumulation there will be alot of debris because of the temperature fluctuations at altitude, though not all of the debris is at the base of the glacier. Further down the the glacier the rocks will have had time to make their way to the base of the glacier by melting down to the base or falling down crevasses. Along the middle and lower part of the profile is where most of the basal erosion will occur. The size of the debris is also a major factor though not as much as the amount because the amount depicts the surface area where as size may affect the surface area of exposed rock but also the volume. Lots of small rocks would mean there is a large surface area and hence a large amount of erosion, but a lot of large rocks means that little of the rock is grinding along the bed and more of the rock is held in the ice. ...read more.

Conclusion

This means the ice moves more and there is more abrasion and a better chance of plucking as well. This happens in the temperate climate, such as the glacier d'Argenti�ne which moves at 250m yr-1 and is 100m thick abraded a marble plate up to 36 mm yr-1. A polar glacier however, Breidamerkurj�kull in Iceland, abraded a marble plate at only 3 mm yr-1 when it was moving at 9.6 m yr-1, however it is only 40m thick. If Breidamerkurj�kull were to accelerate to 15.4 m yr-1 then the rate of erosion increased up to 3.75 mm yr-1. This means that velocity plays a bigger part than the thickness of the ice. In conclusion the all aspects are important to the rates of glacial erosion, but the most important are the velocity of the ice and the hardness of the particles in relation to the bed rock. The amount of the debris is not as important and the size and shape are the least important factors in the rate of erosion. ?? ?? ?? ?? ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Rocks & Weathering section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Rocks & Weathering essays

  1. The aim of this report is to define the geological evolution of the area ...

    There is also a critical change in transport routes along both north and south planes. It is very easy for travel in an East West direction south of the Ochil Hills, something that a few miles north is not possible easily.

  2. Determining the paleoenviroment and tectonic history of a small area (Cocklawburn Beach)

    on a very shallow sea; the roots are from plants that have rooted into the land while it is still underwater. Bed 5: Bed 5 was not thick enough to measure accurately. It is a layer of clay sized grains, and is coal.

  1. 'I think that sedimentary stones will be more affected by weathering than igneous stones.' ...

    quite as successful, because on some stones it is quite hard to see any visual signs of weathering. Generally though, I thought that my methods of grading the rocks went well because if I couldn't grade the rock visually, then I used the thumb method which was very effective in combating this problem.

  2. Find out why there is no Carboniferous Limestone visible around the Somerset area.

    This is to see if the limestone is underneath the Rock that is on top of now possibly. * Check for large scale folding and faulting that is visible. This is to see if the Limestone is below the Rock in a syncline or the faulting may mean that there was Earthquake in the near past.

  1. Construct two Graphic Log Sections, one on the eastern exposure (ST 3375 6645) and ...

    The minerals eg calcite or quartz are derived from fluids and are deposited in faults or fractures. 17 Well-consolidated tuff, dark grey. Calcite veins Well-consolidated tuff means that some pressure has been forced to make it more compact, could be some faulting in earlier beds.

  2. In this Essay I will inform you of the social, economic and environmental advantages/ ...

    so fast to deliver the goods in as little time as possible, and because the quarries don't bother to put covers on the containers of the sandstone(in the shape of large skips,) which are overfilled anyway, hence when the lorries break heavily, the limestone is literally thrown out of the containers and in to the atmosphere.

  1. My aims are to investigate the factors affecting Lava Flows.

    Protractor * Measuring Cylinder Method First I need to collect all the apparatus. I have chosen this list because I think it will give me the most accurate results. Clamp the drainpipe at the end so it is at an angle facing down.

  2. I am trying to find out how footpath erosion on Pen Y Fan which ...

    Backround information on the earths soil erosion problems worldwide. Six to eight inches of topsoil is all that stands between much of the world and starvation. Yet each year a huge amount of agricultural land is lost to erosion, Stalinization (the accumulation of salt in water or soil), and other forms of soil degradation.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work