River Formations Flashcards
V-Shaped Valley
-Vertical erosion is dominant due to the speed of river flow, meaning the water cuts downward into the valley, high on the hillside
-Hydraulic action and solution processed are at work
-Physical weathering weakens the banks of the river. This causes rock to collapse and fall into the river channel
-Swirling water and rocks carried in the river during floods may create potholes, again cutting down into the valley
-The valley becomes steeper and deeper over time and interlocking spurs can occur
Waterfall
-Differential erosion takes place where hard Rock is overlaying softer rock
-Processes of erosion
-The softer rock is more easily eroded by the force of running water as it is less resistant
-This causes overcutting so the harder rock is left overhanging
-The hard rock collapses as there is nothing under it to support it
Meander
-These are long winding bends found in rivers, particularly the middle and lower courses
-Riffles and pools help control the speed of water, increasing and decreasing the rate of erosion
-Where riffles are present the water will flow faster causing erosion further downstream on the outside bend
-Erosion of the outside bend will cause undercutting (processes of erosion) of the riverbank.
This leads to the formation of a river cliff.
-Water will slow down causing deposition further downstream on the outside bend where pools are present
Ox-Bow Lake
-An ox-bow lake started out as a meander and ended up breaking away from the main river channel
-Continual erosion of the outer bends increases the size of meanders
-Processes of erosion
-This causes the neck of the meander to narrow and get closer together
-After a flood or storm, the river will break through the neck when it’s at its most powerful to take the fastest route possible
-Silt and rocks will be dumped and eventually block the flow of the water around the meander and the river will continue to flow straight along the new channel
