glaciation

• the last glacial maximum was 22 thousand years ago and the first interglacial period was 120 thousand years ago
• plucking occurs when the water at the bottom of the glacier freezes onto the valley base and as the glacier moves the rock is pulled away from it
• abrasion occurs when the rocks carried by the glacier grind at the base of the valley
• freeze thaw weathering occurs when water gets into cracks in a rock and expands, causing the crack to widen. when the ice melts more water makes its way into the deepened crack and repeats
• a corrie is an arm-shaped valley formed by glaciers
• an arete is a sharp ridge formed between two or more corries back to back
• when three or more corries erode a mountain back to back, the aretes form a pyramidal peak
• avalanches are formed when snow is compressed and becomes unstable
• avalanches can be managed using fences, warning systems and a trained rescue team