SAJC Prelim_H2_GEO_P1_Mark Scheme

SAJC 2018 Prelims H2 Geography Mark Scheme © SAJC 2018 9751/01/18 Prelims_Page 1 Section A – Tropical Environments Answer one question from this section 1 (a) Explain the variations in rainfall patterns within the tropics. [12] Better responses will be able to integrate the use of variations in annual total rainfall, seasonality in rainfall patterns, sketches of climograph or the use of world map may also be used to support and illustrate the variations in rainfall patterns in the tropics. The predominant mechanism influencing rainfall—seasonal migration of the ITCZ and the resulting movement of the Hadley cell must be explained in detail. The effect of latitude on uneven heating can also be used to explain the presence of convectional rainfall. Other more localised factors like topographical barriers, continentality, ocean currents can also be used to explain variations. Indicative content: (i) Migration of the Hadley Cell a. Influence of the Inter tropical convergence zone b. Influence of Subtropical High (ii) Topographical Barriers (iii) Effect of Continentality (b) Evaluate the extent to which erosion by water is responsible for the formation of landscapes in the arid tropics. [20] Fluvial erosion is not entirely responsible for the formation of arid landscapes, instead the role of Aeolian processes, and specifically erosion and deposition are not to be neglected. The two mechanism tend to work symbiotically, although most landforms are indeed dominantly a result of either fluvial or Aeolian processes. Rills, Gullies & wadis are dominantly the result of fluvial erosion (rill and gully erosion), while yardangs, dunes and deflation hollows are the dominantly the result of Aeolian processes. Better responses will be able to identify how both sets of processes are interlinked in which, one might aid the other e.g. How gully erosion accelerates the initial stages of corridor formation in yardangs. Weakest response would go with simplistic and unbalanced argument on the importance of either water or wind.

SAJC 2018 Prelims H2 Geography Mark Scheme © SAJC 2018 9751/01/18 Prelims_Page 2 2 (a) Using one or more diagrams, explain the relationship between velocity, sediment size and fluvial processes. [12] The Hjulstrom curve ought to be used to illustrate the relationship between velocity, sediment size and fluvial processes. Answers could be organised according to sediment size or fluvial processes. Better responses will also be able to draw upon specific fluvial erosion, transportation and depositional process to support responses. (b) To what extent is climate the most important factor in the formation of different channel patterns in the humid tropics? [20] Responses ought to recognise that beyond the influence of climate, there are also contributing factors leading to the formation of different channel patterns, specifically sediment load and velocity