Mohammed Haye's & Arun Sharma's Page.
Features of Upper course
Waterfalls
How Does A Waterfall Form?
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The soft rock erodes more quickly, undercutting the hard rock.
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The hard rock is left overhanging and because it isn’t supported, it eventually collapse
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The fallen rocks crash into the plunge pool. They swirl around, causing more erosion.
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Over time, this process is repeated and the waterfall moves upstream.
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A steep-sided gorge is formed as the waterfall retreats.
Angel Falls in Venezuela is the world’s tallest waterfall at 979m. A waterfall is a place where water flows over an almost vertical drop in the course of a river or stream. Over time these waterfalls move upriver by a process called waterfall retreat. The waterfall has hard rock which the river flows over and soft rock underneath it. The soft rock will be worn away quicker by the water so the soft rock is undercutting the hard rock and the overhanging hard rock will collapse into the plunge pool. The waterfall then retreats upstream this process can occur aas quickly as 1.5 meters recession per year. When the waterfall retreats a valley with steep sides and a river/stream running across the bottom is formed, this is called a gorge.
Gorges
A gorge is a deep channel formed by a river that has eroded the earth's crust over millions of years. Some gorges are so large they are visible from space. One of the most famous is the Grand Canyon. Gorges are steep sided valleys that have a stream/river running across the bottom. Gorges are left behind when a waterfal retreats.
V-Shaped Valley
In The upper course of a river vertical erosion is more important since the source is almost always above sea level, so the river needs to move downawards to join the ocean. There is a steep decent/gradient in the upper course. V-shaped valleys are formed where the river channel is narrow and fast flowing. Erosional processes such as abrasion and hydraulic action are part of a cause shape of the V-shaped valley causing downward erosion and weakening the sides of rock. However the sides rock are mainly weakened by weathering physical, biological and chemical. Over time it will collapse into the river channel, due to mass movement, then the rocks are carried downstream and broken into sediment and smaller rocks. Vertical erosion is very important in the upper course of a river.
Interlocking Spurs
As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock since it is finding the easiest and fastest way to the ocean, therefore it erodes the soft rock instead.Therefore these spurs are made up of hardrock. When the river is forced to flow around the hard rock multiple times in a row interlocking spurs are created.