Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly. As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity. This causes the waterfall to carve deeper into the bed and to recede upstream.
Often, the rock just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a cave-like formation behind the waterfall. Eventually, the more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These rocks are then broken down into smaller boulders as they collide with each other, and will erode the base of the waterfall, creating a plunge pool or gorge. A fine example of a plunge pool is clearly visible at the EC coordinates.
A river sometimes flows over a large step in the rocks that may have been formed by a fault line. Waterfalls can occur along the edge of a glacial trough, where a stream or river flowing into a glacier continues to flow into a valley after the glacier has receded or melted.
Waterfalls are categorised as follows:
Ledge: Water descends vertically over a vertical cliff, maintaining partial contact with the bedrock.
Block/Sheet: Water descends from a relatively wide stream or river.
Classical: Ledge waterfalls where fall height is nearly equal to stream width, forming a vertical square shape.
Curtain: Ledge waterfalls which descend over a height larger than the width of falling water stream.
Plunge: Fast moving water descends vertically, losing complete contact with the bedrock surface.
Punchbowl: Water descends in a constricted form and then spreads out in a wider pool.
Horsetail: Descending water maintains good contact with bedrock most of the time.
Slide: Water glides down maintaining continuous contact.
Ribbon: Water descends over a long narrow strip.
Chute: A large quantity of water forced through a narrow, vertical passage.
Fan: Water spreads horizontally as it descends while remaining in contact with bedrock.
Cascade: Water descends a series of rock steps.
Tiered/Multi-step/Staircase: A series of waterfalls one after another of roughly the same size each with its own sunken plunge pool.
Cataract: A large, powerful waterfall.
Segmented: Distinctly separate flows of water form as it descends.
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1. Look to the bottom right of the falls, describe what you see here including an estimate of the size, shape, height from bottom of falls, colour of rock etc.
2. What factors do you think have caused this? (looking for more than a one word answer)
3. What is your estimate of the height of the waterfall?
4. Which of the categories above do you think best describes these falls (can be more than one)?
5. Please attach a photo to your log of you, your dog, gps, thumb or something personal to prove you were here. Please do not show any spoilers in your photo.
June 2019 the logging tasks for EC were updated. COs can now insist on a photo as proof of visit.
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