Junior Cert Geography slides on rivers - formation, processes at work, features and how humans use rivers

1. The Work ofThe Work of RiversRivers

2. The 3 Stages ofThe 3 Stages of RiversRivers

3. River StagesRiver Stages
 Youthful or Upper Stage – small fast flowing rivers high upYouthful or Upper Stage – small fast flowing rivers high up
in the mountains.in the mountains. ErosionErosion takes place here.takes place here.
 Mature or Middle Stage – wider but slower rivers flowingMature or Middle Stage – wider but slower rivers flowing
down gentler slopes.down gentler slopes. ErosionErosion andand DepositionDeposition take placetake place
herehere
 Old Age or Lower Stage – Very wide rivers flowing over aOld Age or Lower Stage – Very wide rivers flowing over a
plain as they near the sea.plain as they near the sea. DepositionDeposition takes place here.takes place here.

4. YouthfulYouthful Upper StageUpper Stage
 In this stage the river is flowing down steepIn this stage the river is flowing down steep
slopes and is eroding verticallyslopes and is eroding vertically
EROSION

5. V Shaped ValleyV Shaped Valley

6. How rivers erode (wear awayHow rivers erode (wear away
rocks)rocks)
 Hydraulic Action – the force of moving waterHydraulic Action – the force of moving water
 Abrasion – material carried by the riverAbrasion – material carried by the river
(load) hits against the bed and walls and(load) hits against the bed and walls and
wears them awaywears them away
 Attrition – the load carried by the river areAttrition – the load carried by the river are
worn away themselvesworn away themselves
 Solution – Chemicals in the water breakSolution – Chemicals in the water break
down some rocksdown some rocks

7. Example of V shaped valley = Youthful stage of River
Liffey.

8. Waterfall – Erosion – Youthful Stage.Waterfall – Erosion – Youthful Stage.
 Water from the river flows over the hardWater from the river flows over the hard
rock. Where the water flows over soft rock, itrock. Where the water flows over soft rock, it
can erode or wear this softer rock away.can erode or wear this softer rock away.
 Over time this soft rock is eroded more andOver time this soft rock is eroded more and
more by the water flowing over it. Thismore by the water flowing over it. This
makes a cliff which the water topples overmakes a cliff which the water topples over

9.  At the bottom of the cliff some of the waterAt the bottom of the cliff some of the water
splashes onto the cliff and makes a plungesplashes onto the cliff and makes a plunge
pool by a process known as undercutting. Apool by a process known as undercutting. A
gorge which is a steep sided river valley isgorge which is a steep sided river valley is
often formed by a waterfall .often formed by a waterfall .
 Example -Powerscourt Waterfall.Example -Powerscourt Waterfall.

11. Interlocking SpursInterlocking Spurs
 Bands of harder rock which the riverBands of harder rock which the river
cannot erode straight through and iscannot erode straight through and is
forced to flow aroundforced to flow around
 As the river is forced to “swerve”As the river is forced to “swerve”
around the spurs, lateral (horizontal)around the spurs, lateral (horizontal)
erosion increases due to centrifugalerosion increases due to centrifugal
force – making the curves moreforce – making the curves more
developeddeveloped

12. Interlocking SpursInterlocking Spurs

13. Mature Stage – p32Mature Stage – p32
 This is the next stage of the river as it flows down fromThis is the next stage of the river as it flows down from
mountains – Mature Stage rivers havemountains – Mature Stage rivers have Wide FlooredWide Floored
ValleysValleys withwith Gently Sloping SidesGently Sloping Sides
 Mature stage rivers erode horizontally and there is also
some deposition of material eroded in the upper stage
 Mature stage features - Valley Troughs, Meanders

15. MeandersMeanders

16. AA MeanderMeander

17. 2009 Junior Cert2009 Junior Cert

18. 2011 Junior Cert2011 Junior Cert

19. The Old Age StageThe Old Age Stage
 In the old age stage the river flows over flatIn the old age stage the river flows over flat
plains as it nears the seaplains as it nears the sea
 No EROSION takes place here, onlyNo EROSION takes place here, only
DEPOSITIONDEPOSITION
 Features include Flood Plains, Levees,Features include Flood Plains, Levees,
Oxbow Lakes and DeltasOxbow Lakes and Deltas

20. The Old Age StageThe Old Age Stage

21. A Flood PlainA Flood Plain

22. Ox Bow LakesOx Bow Lakes

23. An Ox Bow LakeAn Ox Bow Lake

24. DeltasDeltas

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27. New Orleans – Hurricane KatrinaNew Orleans – Hurricane Katrina

28. Ardnacrusha DamArdnacrusha Dam

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30. 2007 Junior Cert Exam Question2007 Junior Cert Exam Question