Landforms Flashcards
what river landforms are caused by erosion?
-waterfalls and gorges
-interlocking spurs
where are waterfalls and gorges found?
in the upper course
how are waterfalls and gorges formed?
•softer rock is eroded by hydraulic action and abrasion more than the layer of harder rock over it
•the water erodes the softer rock further undercutting the hard rock and creating a waterfall
•over time the hard rock becomes unsupported and collapses due to erosion. The collapsed rock swirls around the foot of the water fall eroding softer rock by abrasion creating a plunge pool
•Overtime, the waterfall retreats leaving behind a gorge
What are interlocking spurs?
A series of ridges projecting out on alternate sides of a valley and around which a river winds its course.
how are interlocking spurs formed?
•vertical erosion occurs in the upper course creating a v shaped valley
•the river isn’t powerful enough to erode laterally so it winds around hills made of resistant rock
•this creates an interlocking spur
where are interlocking spurs found?
in the upper course of a river where rocks are hard
what are rapids?
fast flowing sections of river where the gradient is quite steep and water is turbulent
how are rapids formed?
they are formed from ridges of harder rock amongst soft rock
where are rapids found?
the upper course
What river landforms are caused by deposition and erosion?
meanders and oxbow lakes
where are meanders and oxbow lakes found?
the middle course
how are meanders formed?
•fast flowing water in the outside bends wear the river away and overtime undercuts the bank
•the river deposits its load of mud and shingle on the inside bend where the river flows slowly
•the outside bend continues to cut into the bank resulting in the river bending more
What does the cross section of a meander look like?
how are oxbow lakes formed?
•the fast flow of water on the outside bend results in erosion
•the outside bends move closer together and the meander neck becomes more narrow
•when there is a high discharge the river cuts across the neck and takes a straight course leaving an oxbow lake
What landforms are caused by deposition?
-floodplains
-levees
-estuaries