WJEC – Geology of the Human Environment (GL3) – May 2002
2.
Figure 2a is a simplified potential radon hazard map for south-west England.
Figure 2b is a simplified geological map of the same area.
Figure 2a
Figure 2b
Source :
Geology Today Vol. 12 No. 2
(Blackwell Science Ltd)
(a)
Refer to Figures 2a and 2b.
(i)
Describe and explain the distribution of high radon
concentrations in south-west England.
[3]
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
…………………………………………………………………………………………
(ii)
Give a reason why radon is hazardous in high concentrations.
[1]
…………………………………………………………………………………………..
(b)
Figure 2c shows variations in radon concentrations related to
subsurface geology.
Figure 2c
(i)
Account for the high concentration of radon gas in the
limestone cavern at location A.
You may annotate Figure 2c in your answer.
[3]
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
(ii)
Explain the effect of one of the following drift deposits on
surface radon concentrations;
EITHER
OR
1. Clay
2. Sand and Gravel.
[3]
State chosen drift deposit ……………………………………….
Explanation…………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
…………………………………………………………………………………………
(c)
Explain how radon gas emissions can be used to predict earthquakes.
[3]
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
………………………………………………………………………………………….
…………………………………………………………………………………………
Total 13 marks
Notes for answers
These represent suggested answers and do not necessarily represent all the possible
acceptable alternatives of a mark scheme.
Question 2
(a)
(i)
(ii)
(b)
(i)
Description - e.g.
3 main area etc.
Area in North
Associated with granite
Explain
Granite Uranium rich
Radioactive breakdown byproduct
Radioactive
Health risk
(max 1)
[1]
One reserved from:
Gas in solution in groundwater
Lower pressure in cave - comes out of solution
Additional answers:
Groundwater flows down fault/fracture zone
Joints/bedding in Lmst. and granite provide pathway
Credit annotation on diagram
(3 max)
(ii)
[3]
1. Clay -
Impermeable
Clay particles/pores small
Pores not connected/sealed
2. S & G -
Permeable
High porosity/large pores
Pores connected
[3]
OR
(c)
Prior to earthquake cracks open/stress increases
Radon gas escapes
Detected radon gas levels rise
Dissolved gas levels in groundwater (wells) increases
Radon levels level off until earthquake
(3 max)
[3]
[3]
Total 13 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