Glacial Landforms: Rock Steps, Truncated Spurs, Hanging Valleys, and Crag & Tail
Explore the formation of unique glacial landforms such as rock steps, truncated spurs, hanging valleys, and crag & tail. Discover how glaciers sculpt these distinct features through processes like erosion and deposition, leaving behind stunning geological formations exemplified in locations like Blencathra. Each landform tells a story of past glaciation and the dynamic forces of nature that have shaped our landscapes.
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Rock Steps Truncated Spurs Hanging Valleys Crag and Tail By Laura Simon David
Rock Steps Rock steps are formed when there are rocks of varying resistances covered by a glacier. If there are sections of harder and more resistant rock they will be more resistant to erosion, through the processes of abrasion and plucking. This means that they will sit higher; like a step. Sections of lower resistance rocks will be more prone to erosion through abrasion and plucking and there will therefore leave a hollow like the ground below the step. This is shown in the diagram below. More Resistant rock Less Resistant rock Less Resistant rock This is a very square and simplified diagram but it shows the basic idea.
Truncated Spurs For a truncated spur to occur, you must have interlocking spurs, which is where a river has eroded away through a valley, where which has harderrock, only eroding the less resistant rock. This then leaves a valley which interlocks each other. However, this is only the first stage in the formation of a truncated spur. Once an interlocking spur has been formed, a glacier then forces itself down the valley, but the sheer force of the glacier is so powerful it bulldozes straight through the interlocking spurs knocking off the ends, and we are then left behind with truncated spurs. A prime example of this is Blencathra, a mountain in the Lake District where a glacier has ploughed through and knocked off the edges. GLACIER PASSES THROUGH
Definition:A blunt-ended, sloping ridge which descends the flank of a valley. Its abrupt termination is normally due to erosion by a glacier which tends to follow a straighter course than the former river; in simple terms, it is an interlocking spur without the land that interlocks! Truncated Spurs can be found anywhere in the world that has been affected by an Ice Age, because a glacier is needed to erode away a valley. Most truncated spurs are found north of 23.5 degrees in places such as Canada, The United Kingdom and Scandinavia.
Hanging Valleys Hanging valleys are the glacial landforms formed when a glacier passes through a main valley with massive erosional power. This causes the main valley to be carved away to form a deeper U shaped valley. While this happens a smaller glacier will pass through the valley of a tributary. This smaller glacier will have a smaller mass and less erosional power meaning that the trough it leaves will be higher. This leaves a valley higher up the wall of the main valley. This normally leads to a waterfall.
Crag and Tail A Crag and Tail; consists of a large mass of resistant rock and a gently sloping tail of less resistant rock. A Crag and Tail is a geological formation caused by the passage of a glacier over an area of hard rock. A good example of crag and tail is the rock on which Edinburgh Castle is built.
Crag Crags are formed when a glacier or ice sheet passes over an area that contains a resilient rock. The force of the glacier erodes the surrounding softer material, leaving a rocky block protruding. It is a results from the abrasive base of a glacier sliding on the land surface.
Tail A tail is softer rock, Crags serves as a potential shelter from a glacier. However usually the Tail has been removed by glacial erosion. Salisbury Crags to the left and Arthur's Seat to the right, with their tails sloping east to the right.
Crag and Tail Vs Rouches moutonnees Crag and tail tends to be larger than a roche moutonnees. Crag and tail is the opposite to the roche moutonnee and has a downslope in the direction of the ice flow.
Now for a Quiz!!!
Question 1 How many different rock hardness's are involved in the formation of a crag and tail? 2 2 1 1 3 3 4 4 Walk Away Walk Away Walk Away Use a lifeline Use a lifeline
Question 2 Which has more eroding power? River River Glacier Glacier Walk Away Walk Away Walk Away Use a lifeline Use a lifeline
Question 3 Which of these are the softest area of rock? Crag Crag Tail Tail Walk Away Walk Away Walk Away Use a lifeline Use a lifeline
Question 4 What is needed to change an interlocking spur into a truncated spur? Ice age Ice age Bulldozer Bulldozer Dynamite Dynamite River River Walk Away Walk Away Walk Away Use a lifeline Use a lifeline
Question 5 Where, in general, are truncated spurs most likely to be found? North of 10 N North of 10 N North of 12.6 N North of 12.6 N North of 10 N North of 12.6 N North of 21.2 N North of 21.2 N North of 23.5 N North of 23.5 N North of 21.2 N North of 23.5 N Walk Away Walk Away Walk Away Use a lifeline
Question 6 Which of these rocks is the most resistant to erosion? Limestone Limestone Slate Slate Granite Granite Chalk Chalk Walk Away Walk Away Walk Away Use a lifeline
Question 7 Crag and Tail has a down slope in the direction of the ice flow. False False True True Walk Away Walk Away Walk Away Use a lifeline
Question 8 Which feature is often found at the end of a hanging valley? Meander Meander Waterfall Waterfall Rock lip Rock lip Dam Dam Walk Away Walk Away Walk Away Use a lifeline
Question 9 Which of these castle are built on an example of Crag and Tail? Alnwick Alnwick Sterling Sterling Dunstanburgh Dunstanburgh Edinburgh Edinburgh Walk Away Walk Away Use a lifeline
Question 10 Which is generally the largest? Roche Moutonnee Roche Moutonnee Crag and Tail Crag and Tail Roche Moutonnee Crag and Tail Walk Away Walk Away Use a lifeline
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