River Processes and Pressures Flashcards
what is hydraulic action?
the force of the water on the bed and banks of the river removes material
what is attrition?
the load that is carried by the river bumps together and wears down into smaller smoother pieces
what is abrasion?
material carried by the river rubs against the bed and banks and wears them away
what is corrosion/solution?
some rock minerals dissolve in the river water
what are the four main types of transportation?
traction
saltation
suspension
solution
what is traction?
large boulders roll along the river bed
what is saltation?
smaller pebbles are bounced along the river bed, picked up and then dropped as the flow of the river changes
what is suspension?
finer sand particles are carried along the river giving a brown appearance
what is solution?
minerals from rocks such as limestone and chalk are dissolved in water and carried along the river
what is transportation?
the way in which the river carries eroded materials
what is deposition?
the river slowing down and dropping some of its load
what is a waterfall?
a steep drop ion a river’s course
how are waterfalls formed?
- a band of resistant rock lays over less resistant rock
- less resistant rock underneath erodes forming an undercut and an overhang
- the overhang can no longer be supported so rocks fall
- the powerful fall of water erodes a plunge pool
what are interlocking spurs?
water flows naturally from side to side of a valley around ridges called spurs which interlock at the other side of the valley
what are meanders?
bends in the river course
how are meanders formed?
the river swings one way and the other causing erosion on the outside bends
how are floodplains formed?
the river deposits sediment on the outside bends after flooding as heavier particles cannot be carried back into river by water
how is an oxbow lake formed?
the neck of a meander narrows cutting it off from the rest of the lake
what are levees?
the build up of floodplains
what are deltas?
a flat area of land created by a build up of sediment
how are deltas formed?
the speed of a river decreases as it approaches the sea so it deposits some of the material it is carrying
how does climate impact transportation rate?
rivers in wet climates transport more material than those in dry climates
how does climate impact weathering processes?
freeze thaw weathering more likely to occur in cold climates
how does climate impact average amount of discharge?
wetter climates mean more discharge than hotter climates where discharge evaporates