Spurs

Spurs are protusions of highlands surrounding the river. There are also two other types of spurs, a interlocking spur, and a truncated spur.


Firstly, the interlocking spur.In the upstream portion of the river, the volume of water is small. Much of the river energy is used to overcome frictionwith the rough channel. There is little energy left for erosion, except during heavy rainfall,when the increased volume causes vertical erosion of the river bed. With little energy left for much erosion, the river flows round hard obstacles of hard rocks such as spurs. In doing so, it develops a winding course. The current is stronger in the outer bank than in the inner bank of the river. Undercutting the outer river bank, as the river swings round alternate spurs on both of its sides, results in spurs that appear to interlock. These results are called interlocking spurs. While similar in general appearance, the mechanism behind the formation of interlocking spurs is different to that behind meandering and they should not be confused.







A truncated spur occurs when the action of a glacier does not follow the original course of the river that wound round interlocking spurs, but, as the force of a glacier is much more powerful and cannot flow as freely around corners, it can carve its way though the rock cutting off the edges of interlocking spurs to form truncated spurs. Hanging valleys are found in between truncated spurs from a side view as the Hanging valleys join the main glacier from an angle. Artificial truncated spur are vastly becoming more popular. They provide good shelter for locals, and good habitat for animals. The valley glacier cannot avoid the interlocking spurs as a river can. As the valley glacier moves, abrasion and plucking erode the protruding tip of the spurs, leaving steep cliff like truncated spurs. Since they are so tall, it is common for many spurs to have a waterfall from them, falling back into the main valley.