Youthful Stage
What shaped valley is commonly found in the youthful stage?
V-Shaped.
Where can meanders be found in Ireland?
River Shannon
What is a delta and how does it form?
Deltas are a triangular, or fan shaped area of land at the end of a river. They form when a river reaches the end of its course and becomes much slower, loses much of its energy and deposits its load. Deltas form in sheltered seas and where river mouths become choked with sediment. This sediment blocks the main channel and causes smaller channels, called distributaries to form.
Describe hydraulic action.
Hydraulic action is when the riverbed and bank are eroded by the force of the moving water, which wears away sand, pebbles, rocks etc.
How do people pollute rivers?
Factories and industries dump waste products into the rivers which can kill plants and animals, destroying the rivers ecosystems.
Farmers spread slurry on the land which can run into rivers killing plants and animals.
List 3 landforms + definitions
V-Shaped valleys, Interlocking spurs, Waterfalls
list three landforms + defs
meanders, oxbow lakes, flood plains
List 3 landforms of the old age stage + definition
Levees, Deltas, Flood Plains.
Difference between attrition and abrasion?
Attrition: Small rocks on the riverbed bash into each other, breaking up into even smaller pebbles.
Abrasion: Stones and rocks rub away at the banks and riverbanks.State the pros and cons of humans building dams:
Bonus (for extra 100 points): What stage of the river is a dam built in?
Pros: Used to supply clean energy (hydroelectricity), can be used to stop flooding (e.g. Aswan, Egypt).
Cons: People may lose their homes to the building of dams, changes the river course forever.
The youthful stage.
How do interlocking spurs form?
Interlocking spurs are fingers of high ground that jut out either side of a V-Shaped valley. The water erodes quickly in the youthful stage, but when it reaches hard rock it cannot erode, it erodes around it instead. The youthful river erodes vertically as it goes. This creates fingers (spurs) of high ground which fit into each other like knuckles.
Formation of a meander?
The river in the mature stage has less speed, more energy, and more water. Lateral erosion takes place as the river erodes the riverbanks. The river moves faster on the outside, and because of hydraulic action the outside curve is eroded quicker. The river moves slower on the inside curve and some of the eroded material is deposited there, sometimes creating a point bar. Over time this is repeated, created a very pronounced S-shaped bend.
Explain how flood plains form.
Flood plains are wide flat areas of land on either side of the river in its old age stage. They are formed when the river is carrying a massive load e.g. alluvium (very fertile soil particles, crucial to farming), but after times of heavy rainfall, the river may burst its banks and flood the surrounding area. The river will deposit the heaviest material first, e.g. rocks, and deposit the lighter stuff further away (alluvium). Over time, a thick layer of fertile soil with build up on the flat ground next to the river (great for farmers).
What is deposition?
Deposition is when the river slows down, or the river's load becomes too much to carry, so it deposits some of its load.
List all methods of river transportation.
Saltation (Bouncing), Traction (Rolling), Floatation, Solution, Suspension
How is a waterfall formed? Explain in detail.
When a river flows over a section of hard rock (e.g. granite), with soft rock (e.g. limestone) underneath, the soft rock is vertically eroded (by hydraulic action + attrition etc), creating a vertical drop in the riverbed. This is a waterfall. As the drop gets larger, the water hits the riverbed harder, eroding more, creating a plunge pool (abrasion). The splashing water hits the back wall of the waterfall, which is made of soft rock, and undercuts it through solution, creating an overhang. This process repeats itself, causing the waterfall to retreat back upstream, creating a gorge.
River Liffey and River Moy
What are levees, and how do they form?
A raised riverbank created by repeated flooding and deposition of alluvium. At times of low flood, material is deposited on the riverbed but in times of flood, when the river bursts its banks it deposits large and heavy material e.g. large rocks right next to the river. Over time this builds up and creates a barrier next to the river, which helps prevent future flooding.
What processes occur in the mature stage?
Deposition and Erosion
Name five Irish rivers.
Answers include: Liffey, Shannon, Garavogue, Lee, Barrow, Suir, Blackwater, Nore.