Patterned ground formation
Explain the formation of patterned ground and stone stripes. (15 marks)
Patterned ground is a very distinct feature in peri-glacial regions, and is found in places such as the Antarctic Peninsula. They generally take the form of a polygons (which may form tessellations), or circles. It is caused by a process called frost heave, and can in some cases be the result of stone stripes.
Frost heave is the initial cause of patterned ground, and this process is a result of the summer months melting the top one metre of ice, called the active layer. This layer contains both water and mud, which both have different viscosities and therefore different specific heat capacities. During the three months of summer, when the active layer is visible, rocks will embed themselves into it. These rocks have a fairly high specific heat capacity in relation to ice, so the ice around it will be melted, and the process of percolation will cause a pool of water will form below the rock. As the temperature drops and the angle of incidence is further from the sun, the water will begin to freeze. Due to the chemistry of the water, it can freeze and expand when it drops below a certain temperature, around 0 degrees Celsius. Frozen water will take up a certain amount of space, and when it melts, 9% of the space it previously occupied will be disused. The melted water beneath the rock will expand when it freezes and fill up the extra 9% of space, however due to the fact there is a rock above it, the ice will force the rock upwards. As the stone ascends it pushes the finer sediment above it upwards too, creating a more compacted dome of finer material at the surface. This process is called frost heave. Consequently, the ground above the rock will be pushed upwards; creating a contour, but the ground around the land will stay the same. Inside the active layer the water is not equally spread throughout. In addition to this, there will be many rocks that are affected by frost heave, and all of
Patterned ground is a very distinct feature in peri-glacial regions, and is found in places such as the Antarctic Peninsula. They generally take the form of a polygons (which may form tessellations), or circles. It is caused by a process called frost heave, and can in some cases be the result of stone stripes.
Frost heave is the initial cause of patterned ground, and this process is a result of the summer months melting the top one metre of ice, called the active layer. This layer contains both water and mud, which both have different viscosities and therefore different specific heat capacities. During the three months of summer, when the active layer is visible, rocks will embed themselves into it. These rocks have a fairly high specific heat capacity in relation to ice, so the ice around it will be melted, and the process of percolation will cause a pool of water will form below the rock. As the temperature drops and the angle of incidence is further from the sun, the water will begin to freeze. Due to the chemistry of the water, it can freeze and expand when it drops below a certain temperature, around 0 degrees Celsius. Frozen water will take up a certain amount of space, and when it melts, 9% of the space it previously occupied will be disused. The melted water beneath the rock will expand when it freezes and fill up the extra 9% of space, however due to the fact there is a rock above it, the ice will force the rock upwards. As the stone ascends it pushes the finer sediment above it upwards too, creating a more compacted dome of finer material at the surface. This process is called frost heave. Consequently, the ground above the rock will be pushed upwards; creating a contour, but the ground around the land will stay the same. Inside the active layer the water is not equally spread throughout. In addition to this, there will be many rocks that are affected by frost heave, and all of