Cold Environments: Processes in Glacial Landscapes

Cold Environments: Processes in Glacial Landscapes

1. Weathering in a Cold Environment

   • Weathering is defined as the breakdown of rock in situ (original position), at or just below the ground surface
   • Frost Shattering/Freeze Thaw: Commonly affects bare rocky outcrops high up on a mountainside. Water finds its way in between cracks in the rock, the temperature drops to 0 or below and the water turns to ice. This then causes, what used to be water but is now ice, to expand and crack the rock. The ice then melt when the temperature raises again.
   • Frost shattered rocks are sharp and angular. As they become trapped under the ice, they prove to be a good abrasive tool.

2. Glacial Processes

   • Abrasion: The sandpapering effect of glacial ice as it moves over the landscape. Striations are carved out because of this. Over time, the big rocks used to abrade the landscape become pulverized by the weight of the glacial ice and become fine rock flour.
   • Plucking: This occurs when the refreezing of meltwater freezes part of the underlying bedrock to the base of the glacier. Loosened rock fragments are 'plucked' away when the glacier moves forward.
   • A roche mountonnee would have acted like an obstacle to a glacier moving down the valley. The process of abrasion eroded the stoss side, and the process of plucking eroded the lee side
   • Carbonation: This is the process of chemical weathering that involves the slow dissolving of calcium carbonate in some rocks-particularly limestone. CO2 dissolved in water forms a weak carbonic acid, which reacts with calcium carbonate in the rocks to form calcium bicarbonate, which then dissolves. The lower the temperature, the more effective carbonation will be.