rivers Flashcards
what is the definition of erosion and deposition
the wearing away of the land by material carried by rivers, glaciers, waves, and the wind
the laying down of material carried by rivers, seas, ice and wind
what are the three main roles of a river ?
upper middle and lower stage
what is the river basin system ?
- river has a scorce
- flow in channels
- collect water from tributaries
- rivers have a mouth in either a lake or sea
5 river basin bordered by a watership can collect water from a wide area
what are the characeristics of the upper, middle, and lower stage
1.vally shape and gradient
2. channel depth
3. main process
4. load size and type
5. characteristics landforms and features
upper
1. narrow V shaped valley with a steep gradient.
2. channel is shallow and the water is fast flowing
3. vertical erosion, weathering on the slopes and trasportation.
4. load size is large and angular
middle
1. valley is still V shaped but less steep
2. channel is deeper and wider
3. vertical erosion, decreasing in importance. More lateral (sideways) erosion and deposition
4. load becomes smaller and less angular
5. floodplane is begining to form and meanders are clear. ox-bow lakes
lower
1. the river flows over the land with a very gentle gradient (quite flat)
2. channel is at its widest and deepest, and may be tidal.
3. deposition more important than erosion
4. large amount of load but size is very small and rounded
5. levees, floodplains, terrances, deltas and etaries
how do rivers shape the land ?
when the channel is unstable erossion can happen on the sides causing the river to meander from side to side
what are the four main process of erosion
attrition) material is moved along the bed of the rivers , collides with other
material, and break up into smaller pieces.
abrasion) fine material rubs against the river banks. the bank is worn away, by sand papering action and collapses
corrosion) some rocks forming the banks and bed of a river are dissolved by acids in the water.
hydraluric action) the sheer force of water hitting the banks of the river.
what four main processes of transportation
traction) larger rocks and boulders are rolled along the bed of the river
saltation) smaller stones are bounced along the bed of a river in a leap frogging motion.
suspension) fine material, light enough in weight to be carried by the river. it is this material that discolours the water.
solution) dissolved material is transported by the river.
landforms in the upper stage of the river what are potholes
are smooth rounderd holes formed in a bedrock of a river by vertical erosion. stoned trapped in hollow in bedrock are swirled around by currents in the water.
these stones “drill” drown into the rock and create potholes
what are rapids ?
rapids form in places where the water is shallow and the river bed is rocky and irregular- making the water rough. along the river’s corse. They can be cause by bands, or band of rock in the river bed.
what are the stages of waterfalls ?
1) waterfalls from where a horizontal layer of hard rocks lies on top or a layer of soft rock in a river
2) the soft rock starts to wear away creating a plunge pool to develop.
3) the splashing waters and edgy current in the plunge pool undercut the hard rock layer above. The hard rock eventually creates an unsupported overhang collapses.
4) if the process of undercutting and collapsing is repeated over a long period of time, the waterfall will retreat upstream forming a deep steep-sided valley called a gorge
what is a flood plain
the flat area of land over which a river meanders is called a flood plain. during times of the flood, a river will overflow its banks and cover any surrounding flat land
