physical environment Flashcards
glaciated uplands
what is freeze-thaw weathering?
rainwater enters cracks in rocks and, in winter this water freezes. when it freezes and expands, this forces the crack to widen.the process repeats thousands of times, pieces of rocks break off.
what is plucking?
between the glacier and the rock underneath is a thin film of melt water. this water sometimes freezes so the glacier becomes attached to the rock. then, when the glacier moves forward, it pulls away loose fragments of rock.
what is abrasion?
this is when a rock is frozen into the glaciers ice. the glacier moves and the rocks scrape along the valley floor and therefore erode it.
explain the formations of a corrie?
snow fills a north facing hollow and is compressed and turns into ice. the ice moves downhill due to gravity. abrasion takes place on the corrie floor, plucking at the back wall and freeze-thaw at the back helps steepen the back wall. when the ice melts an arm chair shaped hollow is left called a corrie. a lip, made from moraine, is left at the front as ice loses power. when water remains in the corrie it is called a lochan or tarn.
what is an arete?
where two corries from back to back or side to side, the rock between them was plucked away to from a narrow ridge. this steep and narrow knife-like ridge is an arete.
what is a pyramidal peak?
Where three or more corries are formed back to back, the rock between them was plucked and weathered into a sharp point, usually the highest point in the area.
how is a u-shaped valley made?
Before Glaciation a v-shaped valley exists. During the ice age a glacier moves downhill eroding the sides and bottom of the valley, through plucking and abrasion. Through erosion this makes the valley sides steeper and the valley deeper. After the ice melts a steep, deep, flat floored U-Shaped valley remains. The original stream now seems too small for the valley and is called a misfit stream.
what is a truncated spur?
A spur is the bottom part of a ridge which juts out into the main valley. A river winds around spurs in a v-shaped valley.
how is a truncated spur formed?
During the ice-age a glacier moves down the valley. The sides of the valley are eroded by abrasion and the spurs are worn away. After the ice age the valley is wider and straighter and the spurs have been cut off leaving shortened or truncated spurs.
how is a hanging valley made?
A large glacier occupies a main river valley and a smaller glacier occupies the tributary valley. As the glaciers move they erode the sides and bottom of the valleys, through plucking and abrasion making the valleys wider, deeper and steeper. When the ice melts the tributary valley is left suspended above the main u-shaped valley as it was not eroded as much because the smaller glacier had less power so there was less erosion The tributary river now has a waterfall
explain why there can be a ribbon lake
The material which was pushed in front of the glacier and left as the glacier melted, is called terminal moraine. This material may be large enough to form a dam at the end of the U-shaped valley. The stream cannot proceed further and gradually backs up. The valley was then flooded and the shape of the resulting lake or rock resembled a piece of ribbon stretching back through the length of the valley.
