Rivers - created from Mind Map

Página 1

Youthful stage

A waterfall is a key example of river erosion

A waterfall is found in the youthful stage of the river cycle

An Irish example of a waterfall is Powerscourt waterfall in the Dublin/Wicklow mountains

An international example is Niagra Falls in Canada

The main erosion technique used in waterfalls is hydraulic action

Hydraulic action occurs when water flows from hard rock to soft rock

An example of Hard rock would be quartzite and an example of soft rock would be limestone.

The soft rock in the river bed is eroded more quickly than that of the hard rock

As the soft rock is eroded away a steep gradient becomes more promenent giving us the starting shape of what we know as a waterfall.

The base of the waterfall becomes even more pronounced with excess pressure from the water creating a plunge pool

The next feature of the waterfall is an overhang

An overhang is formed from the water undercutting the edge of the waterfall

From excess erosion and the weight of the overhang it collapses restarting the process returning to its previous state

This process repeats itself over and over again and the waterfall begins to retreat upstream

Mature Stage:

A meander is an example of river erosion, transportation and deposition

A meander is found in the mature stage of the River Cycle

An irish example is the River Shannon and an international example is the River Mississippi in America

The main erosion technique that occurs is hydraulic action

Hydraulic action is the power of water to erode the river side and bed

As the river erodes its sides and bed the rocks, soils and silts are transported quickly downstream

As the river slows down going around the bends of the meander the transported soils and silts are deposited on the opposite side of the river bend

The erosion of one side of the river sides and the build up of these sands and silts is what creates the twisting and meandering shape of a meander

Through excess erosion an ox bow lake is formed

A river will always try to find the weakest point in the river banks aiming to cut through sharp river bends

Through excess hydraulic action the water will break through at a weak point in the river bark

Deposition at the opening of this weak point closes off the horse shoe shape of the bend leaving a "U" shape feature removed from the flowing water

This u shape feature found internationally is known as an ox bow lake

Old Stage:

A delta is an example of river transportation and deposition

a Delta is found in the old stage of a river cycle

An Irish example of a Delta is dublin bay in dublin city and an international example is the Nile Delta in Egypt

A Delta is the last formation found along the river course

Eroded silts and sands are transported downstream from the mature section of the river course leading to the formation of delta

The main erosion technique that creates these silts is Hydraulic Action

Hydraulic action is the power of water used to erode away a river bed and sides

As the river couse becomes wider it loses power and slows down

Coming into the latter stages of the river cycle these sands ans islts are deposited at the mouth of the river

The mouth of the river is locatde where fresh wate ( River ) meets salt water (sea).

A delta prevents salt water from following upstream and destroying freshwater eco-systems

An arrow shape formation fo alluvial silts is deposited leaving us with the formation we see today

The alluvial silts deposited are hard sought after with the use of silts used in farming leaving extremely fertile soils

Rivers