The upper course
\nDifferent river processes lead to different landforms.
\nIn areas where vertical erosion is dominant \u2013 waterfalls and gorges are commonly found
\nIn areas where lateral erosion and deposition become more important – meanders and oxbow lakes develop
\nIn areas where deposition is the most significant process \u2013 floodplains and levees become a key aspect of the landscape.<\/p>\n
Waterfalls
\nPicture
\nFormation of a waterfall:
\n1.Waterfalls are found in the upper course of a river. They usually occur where
\na band of hard rock lies next to soft rock. They may often start as
\nrapids.
\n2. As the river passes over the hard rock, the soft rock below is
\neroded (worn away) more quickly than the hard rock leaving the hard rock
\nelevated above the stream bed below.
\n3. The ‘step’ in the river bed continues to develop as the river flows over the hard rock step (Cap Rock) as a vertical drop.
\n4. The drop gets steeper as the river erodes the soft rock beneath by
\nprocesses such as abrasion and hydraulic action. A plunge pool forms at the base
\nof the waterfall.
\n5. This erosion gradually undercuts the hard rock and the
\nplunge pool gets bigger due to further hydraulic action and abrasion. Eventually
\nthe hard cap rock is unsupported and collapses. The rocks that fall into the
\nplunge pool will continue to enlarge it by abrasion as they are swirled around.
\nA steep sided valley known as a gorge is left behind and as the process
\ncontinues the waterfall gradually retreats upstream.
\nLots of useful weblinks
\nVideo on how waterfalls are formed –
\nhttp:\/\/www.bbc.co.uk\/learningzone\/clips\/waterfalls-geology-and-formation\/4314.html
\nVideo on waterfalls, plunge pool and potholes –
\nhttp:\/\/www.bbc.co.uk\/learningzone\/clips\/waterfalls-plunge-pools-and-potholes\/404.html<\/p>\n
How are gorges formed?<\/p>\n
A gorge is a steep-sided valley in the upper course of the river. It is usually v-shaped.
\nhttp:\/\/www.cleo.net.uk\/resources\/displayframe.php?src=307\/consultants_resources%2F_files%2Fgorge.swf
\nVideo on the formation of gorges –
\nhttp:\/\/www.bbc.co.uk\/learningzone\/clips\/waterfalls-and-gorges-erosion-and-deposition\/3239.html<\/p>\n","protected":false},"excerpt":{"rendered":"