+++++Rivers Flashcards
What is a river
A river is fresh water flowing across the surface of the Land usually to the sea
List the stages of a river
Youth maturity and old age
Erosion definition
The River wears away the landscape
Transportation definition
The river carries the eroded material away
Deposition definition
The river drops the material it is carrying
Processes of river erosion
hydraulic action abrasion attrition solution
What is hydraulic action
The power of the water that helps to erode away rock over time
What is abrasion
The eroding away of the river bed and river bank by the load carried by the water
What is attrition
The hitting of pebbles of each other causing them to become round and smooth
What is solution
The water can dissolve some of the minerals example: limestone on the river bed and Banks
Processes of river Transportation
Rolling (traction),bouncing (saltation), suspension and solution
What is rolling or traction
Large Stones rolled at high flow
What is bouncing or saltation
The Hopping motion of pebbles
What is suspension
Small particles held up with in the water
What is Solution
Rocks that have been dissolved into the water by weak acids
What is river deposition
Rivers deposit or drop the load when they begin to slow down and lose energy
Examples of rivers losing energy
When a river reaches flat ground or enters a lake or sea
Or at the inside bend of a meander
A detailed description of a meander
It is deposition and erosion together
It is found in an old stage and mature river
Example: mature stage of the river shannon
Water flows quickly on the outside of the River Bend.
The river erodes the bend by a combination of hydraulic action and abrasion.
Water flows more slowly on the inside bend of the river.
Material is deposited on the inside bend as the river loses energy here.
This causes the river the curve
Example of river deposition
A meander
A detailed description of an oxbow lake
They are horse-shoe shaped lakes found on the flood plain of old rivers. They are formed by river erosion and deposition. An example can be seen in the river Moy.
- Erosion by hydraulic action and abrasion takes place on the outside bank of the meander. The neck of land between the meander begins to narrow.
- During times of flood, the water has increased energy. It takes the shortest course by breaking through the neck and begins to flow in a new, more direct course.
- Deposits of alluvium (fertile soil) now build up and seal off both ends of the meander. The old section of the meander is now cut off from the main river and becomes known as an ox-bow lake. Over time, the lake may dry up.
