Revision ~ River Environments

1. Revision ~ River Environments Work covered here links with your revision guides and you will need them for revision lessons. River Environment

2. Mechanical Weathering • Rock crystals expand and contract • Water expands 9% when it freezes to form ice • As crystals grow they exert pressure • Weight is taken off the rock • Surface layer flakes off • Expands when wet and contracts when dry • Jointed rock • Freeze thaw • Salt Crystal growth • Exfoliation • Wet/dry • Granular disintegration • Block disintegration • Pressure release Match the starter with the correct ending

3. Which mechanical processes are shown in the photographs?

4. Chemical weathering • This affects rocks which contain calcium carbonate such as limestone and chalk • When minerals absorb water, expand and change • Oxygen reacts with minerals like iron (rusts) • This affects rocks with feldspar minerals leaving behind clay • Oxidation • Carbonation • Hydrolysis • Hydration Can you top and tail again?

5. Which chemical processes are shown in the photographs?

6. Biological weathering Chemical weathering – Lichens, bacteria ~ organic acids dissolve Plants~ mechanical weathering ~roots exert pressure

7. Climate is a vital factor what influences weathering processes. What trends does Peltier’s model reveal? Can you name another factor which influences weathering processes? GEOLOGY

8. Mass Movement Remember….. The processes that shape a river environment are also affected by slope processes as well as weathering processes. Mass movement is…. The movement of material under the force of gravity. It tends to reduce the slope angle, It is classified on speed and water content Slow ~ soil creep and rain splash Fast ~ flows like sheetwash (wet), slides and slumps (dry) Very fast~ falls, avalanches

9. Can you identify the different slope processes?

10. Factors which control type and rate of movement~ • Climate • Rock type • Rock structure • Relief • Vegetation • Drainage • Aspect • Rate of erosion • Human activity

11. Precipitation Evapotranspiration Transpiration Vegetation (interception) Surface runoff Evaporation Surface Storage Channel flow infiltration Throughflow Soil Storage percolation Groundwater flow Groundwater Storage River Drainage Basin System

12. Factors responsible for fluvial processes and landforms~ Types of flow~ Laminar and turbulent Channel shape~ look at wetted perimeter and hydraulic radius ~ Channel size~larger channels are more efficient Channel roughness~ mannings “n” Gradient~ steeper gradient faster the flow? Load~ greatest at time of flood, smaller and smoother at mouth Base level~ change in sea level How do these change from source to mouth? Should be able to list physical and human factors

13. Basin factors~ Size of basin, shape of basin, river network(pattern), river density These can and will affect a hydrograph

14. Processes of Erosion~ Abrasion~load wearing away banks Hydraulic action~ force and weight of water Attrition~ load collides and grinds away Solution~ removal of chemical ions www.gatm.org.uk

15. V shaped valleys (Erosion) V Shaped Valley Video

16. Waterfalls & gorges (Erosion) Waterfall Video

17. Transportation processes~ Traction~ rolled along the bed Saltation~ bouncing along the bed Solution~ dissolved in the water Suspension~ held in the water Hjulstrom Curve

18. Deposition processes~ • Deposition takes place when~ • There is a shallowing of the gradient which decreases velocity and energy • A decrease in the volume of water in the river • An increase in the friction between water and the channel • Human obstructions such as dams

19. Meanders (Erosion & Deposition) Meanders Video

21. Ox bow lakes (Erosion & Deposition) Describe the processes

22. Braided Channels (Deposition) Braided Channels

23. Floodplain (Deposition)

24. Delta (Deposition) Deltas Video