Rivers Flashcards
What features do you find in the upper course? (4)
Waterfalls, gorges, V-shaped valleys, interlocking spurs
What features do you find in the middle course? (3)
meanders, floodplains, oxbow lakes
What features do you find in the lower course? (4)
floodplains, mud flats, deltas, estuaries.
Where do you find a waterfall?
upper course
Where do you find interlocking spurs?
upper course
Where do you find a gorge?
upper course
Where do you find a v-shaped valley?
upper course
Where do you find an oxbow lake?
middle course
Where do you find a meander?
middle course
Where do you find floodplains?
middle course or lower course
Where do you find mud flats?
lower course
Where do you find a delta?
In the lower course, where a river empties into another body of water
Where do you find an estuary?
lower course
How is a waterfall formed?
when a river starts flowing over harder rock. The water vertically erodes the softer rock, and eventually starts undercutting the hard rock. Over time, the overhang of harder will be less and less supported, and eventually fall into a plunge pool. It will eventually retreat up[ the river.
What type of erosion happens when a waterfall retreating backwards?
Headward erosion
What is headward erosion?
When a waterfall retreats backwards up a river
What is a plunge pool?
The deep pool found at the bottom of a waterfall.
What types of erosion create a plunge pool?
Hydraulic action and abrasion
What is undercutting?
When the soft rock under the hard rock in a waterfall is eroded faster than the harder rock.
When the hard rock falls into the river what is it called?
Load
How is a gorge formed?
When a waterfall retreats backwards and leave a steep sided valley
How are interlocking spurs formed?
Since a river is “Lazy”, it will take the shortest route- around the bases of hills. It will flow around them instead of “bothering” to cut a path through harder rock.
How are v-shaped valleys formed?
V-shaped valleys are formed when a small stream naturally follows small depressions in the landscape, and over time weathering and gravity will wear away the steep valley sides. This forces material into the streams, which cuts the valley deeper. The bedload will helps the vertical erosion, making the sides steeper and more exposed.
What is bedload?
What is carried along the floor of a river
What is load?
Everything the river carries
What is discharge?
the volume of water carried by a river
What is braiding?
A network of rivers seperated by small often temporary islands.
What are braid bars?
The small islands in a braided river
What is abrasion?
When pebbles grind along the river bank and bed in a sand-papering effect.
What is attrition?
When stones in the river knock against each other, gradually making them smaller and rounder
What is hydraulic action?
This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks of the river bank and bed, and causes the rock to break apart.
What is solution? (erosion)
When water dissolves soluble materials from the bank or bed, which breaks them up.
What is vertical erosion?
When gravity pulls the water down to erode the bed.
What is lateral erosion?
Erosion of the banks, rather than the bed
what is suspension? (load)
Fine, light materials carried by a river
What is traction?
large boulders and rocks carried along the river bed
What is solution (load)?
materials dissolved in the river
what is a confluence?
When two rivers meet
How is an oxbow lake formed?
when the neck of a meander gets thinner and thinner, and eventually forms two paths in the river that eventually meet up: one that goes round the original meander and one that goes the quicker, straighter route. The route to the original path eventually gets blocked off, and then the oxbow lake is left. It will eventually get filled in.
What is the difference between a delta and an estuary?
an estuary is where freshwater meets saltwater, and it only happens in seas. A delta can happen in the lakes as well and it
What is the key process in forming estuaries?
deposition
What word can be used to describe a river at an estuary?
Tidal
How does depostion occur in a delta?
When the river slows down, the load carried by the delta will be dropped off. Sometimes there is so much of it the river can’t carry it away.
What are the causes of flooding?
Built-up areas, deforestation, downhill slopes, lots of precipitation, snow melting, impermeable rock, settlements built on floodplains, already wet ground, dry ground.
What does impermeable mean?
fluids can’t pass through it
What does saturated mean? (In terms of flooding)
When the ground holds too much water and can’t take any more
What is transportation?
When a river carries its load from one place to another
What counts as load?
pebbles, sand,mud,rocks
What is the difference between saltation and suspension and solution? (3 points)
Suspension is when load is dissolved (suspended) in the water , saltation is where pebbles are bounced along the riverbed , mostly near the source , solution is dissolved chemicals
What is traction?
large heavy pebbles rolled along riverbed
where is load largest?
near source
What does watershed mean?
The circumference of the drainage basin; inside it any water will go into the river
Why might a river deposit its load?
River slowing down, getting shallower, less volume
