Paper 1 · slope morphology data analysis
A field survey compared slope profiles in two valleys: a limestone valley where maximum slope angles ranged from 17 to 32 degrees with no concave sections recorded, and a clay valley where maximum slope angles ranged from only 2 to 9 degrees with 68% to 80% of each profile concave. What best explains why the limestone slopes are so much steeper than the clay slopes?
ALimestone is a resistant, well-jointed rock that can maintain steep gradients, while clay is weak and easily eroded, producing gentle, concave profiles.
BThe limestone valley receives far more rainfall than the clay valley every year, and this extra rainfall is what causes the sharper erosion seen near the top of each slope profile.
CThe clay valley lies at a much higher altitude, where colder temperatures reduce the maximum angle a slope can sustain.
DThe limestone slopes have not yet been exposed to any weathering processes, unlike the older clay slopes.
Explanation: Limestone is a resistant, well-jointed rock capable of sustaining steep gradients maintained largely by surface wash and creep, whereas clay is a weak material that slumps and is redistributed downslope, producing the gentle, concave profiles recorded in the clay valley. Rainfall amount, altitude and relative age are not given as differences between the two valleys in the survey.
Derived from ZIMSEC Geography Paper 1, November 2003, Q2
