Mark Brodie (
Geoscientist August 2013) is a good example of why an individual mapping project should be an essential part of an undergraduate course in earth science. Mark did not see the point of it. But it is the first, and for some geologists perhaps the only occasion on which he/she has to gather data in the field and make a three-dimensional interpretation of it. Many geologists to-day may never see an outcrop in the course of their work, unless perhaps on a field trip for professionals. Or, indeed, actually handle a piece of the rock which they are drilling through.
I do agree with Mark that the interpretation of geophysical borehole logs should also be taught – having had occasion to use borehole logs and having had to teach myself. The basic principles are not difficult to understand and it wouldn’t take very long. And how about seismic interpretation, now much more sophisticated than in my early days.
Coming back to mapping, the chief fount of expertise in the art has always been the British Geological Survey. Their geologists have mapped all of England and Wales and much of Scotland on a scale of 1:10 000, new recruits being trained by their experienced colleagues. Over much of lowland Britain, where you hardly ever see a natural rock exposure, this is a skill not to be sneezed at, and far superior to what can be acquired during a student project. But do we need it any more? The last BGS printed catalogue, 2010, shows coverage of England and Wales complete at the 1:50 000 scale, except for 21 sheets (out of 356) only available at 1 inch to a mile, and nine which are presumably unavailable colour printed (‘contact the sales desk ..’).
Six-inch, later 1:10 000 revision of the earlier maps was begun more than a century ago and is, I believe, virtually complete. Quality of work no doubt varies but information on local geology based on large scale mapping is generally available. The six-inch originals can be examined at BGS offices. So do we still need to know how to do it?
It can be argued that revision of the national mapping can never be finished. A recent example is the Chalk. For most of the 20th Century three divisions were mapped: Lower, Middle and Upper Chalk, and these were used, for example, in a partial six-inch revision of the Shaftesbury (313) One-Inch sheet in 1923. Towards the end of the century the area was again revised, and ‘it was found that the Chalk could be divided into nine mappable units … in the Shaftesbury and adjacent districts.’ (Bristow et al. 1995, 111) and these were shown in the 1993 map. Similar refinements may be found in other rock groups. And what about the vast areas of Triassic mudstones, showing no faults because they could not be mapped, or faults shown on the Dorset coast which are not continued inland? In any case some of the earlier six-inch revisions are certainly capable of improvement.
I doubt this is the present philosophy of BGS. Mapping gets more and more time-consuming and more and more expensive, though air photography and satellite imagery can help, as in the Shaftesbury case. A new revision is surely something that any public servant would view with horror !
Reference
Bristow, C R, & 7 others, 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey.