WJEC – Geology of the Human Environment (GL3) – May 2005
1.Figure 1a shows the location of the Vaiont dam and reservoir, Italy, which
suffered major landslides in the 1960s. Figure 1b is a geological cross section across the Vaiont valley. Figure 1c shows the relationship between landslide movement and reservoir levels.
Figure 1a
Figure 1b
Figure 1c
(a)Refer to Figures 1a and 1b.
(i) Suggest one possible geological reason for the location of the dam. [1]
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(ii)Explain how the following geological factors made the
VaiontValley suitable as a reservoir site.[4)]
1. The shape of the valley…………………………………………………
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2. The broad geological structure (indicated by dip arrows). …………….
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(b) Refer to the data in Figures 1b and 1c as appropriate.
(i)Draw in a line on Figure 1b to show the maximum height of
the reservoir in 1963.[1]
(ii)Describe the relationship between slope movement (Slide A) and reservoir levels during 1960-61 in Figure 1c. [2]
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(iii) Explain how geological structure, rock type and reservoir levels contributed to the major 1963 slide (B). [4]
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Total 12 marks
Notes for answers
These represent suggested answers and do not necessarily represent all the possible acceptable alternatives of a mark scheme.
Question 1
(a)(i) valley narrowest here
rock strength
impermeable rock
other sensible
(max 1 mark)[1]
(ii)1. Long and narrow/deep
Less water surface area exposed to evaporation
(max 2 marks)
2. syncline-keep water in
(max 2 marks)[4]
(b)(i)Height drawn a approx. 710m[1]
(ii)Higher level - greater movement
Some quantification - 650m = over 3cm/day[2]
(iii)Structure - Dipping beds, critical stable angles
Rock Type - Permeable limestone over impermeable clay
Reservoir levels - High levels - high pore pressure in saturated rock
Other - e.g Accept
high rainfall caused higher water table
rapid reduction in res. level prior to slide caused explosive effect of pore water with high water table.
(1 mark for EACH plus 1 other)
Holistic - credit for argument and additional knowledge.[4]
Total 12 marks
ESTA would like to thank the WJEC for allowing this question to be published on GEOTREX. Any comments should be directed to the Subject Officer for Geology at the WJEC. 15/04/2007