230 BOOK REVIEWS

desirability of putting together on an engineering geo­morphological/engineering geological map all relevanttopographic, morphological, geological, hydrogeologicaland human-made features, derived from air photos, archivalsearches, field checks, etc. Trial pits are mentioned, butcould well have been given greater prominence: the needfor the utmost care with regard to the safety of these shouldalso have been emphasized. There is no mention of the needto be aware of the possible presence of slip surfaces pro­duced by processes other than landsliding, for exampleby tectonically generated flexural slip.

The strength of rocks and soils is not dealt with well.There is no mention, for instance, of drained and undrainedshear strength, of laboratory or in situ methods of measur­ing these, or of stress paths. A section is devoted to RockMass Strength, but soil mass strength and sample sizeeffects in soils, neglect of which continues to give rise toexpensive failures, are not mentioned.

Subsidence, as befits a book coming out of Nottingham,is handled better, with sections on Subsidence, Subsidenceon Clays (it would be clearer if this were to be termedconsolidation), Subsidence on Limestone, Subsidence overOld Mines, and Mining Subsidence (referring to totalextraction by longwall mining).

Slope instability is treated in sections on Slope Failureand Landslides, Water in Landslides, Soil Failures andFlowslides, Landslide Hazards, and Slope Stabilisation. Theslide c1assfication system used omits the important group oftranslational slides (although the Gros Ventre slide is illus­trated) and confuses mudslides and mudflows (the latter arenow generally termed debris flows). Although c and c' and1'1 and 1'1' are defined in the Appendix, they are used ratherindiscriminately in the text. On p. 68, it is stated that'London Clay has 1'1£ = 20°; slopes are stable at < 10°, anddo not exist at > 12°.' In fact, 20° is the peak effectivefriction angle for the London Clay, natural slopes in thismaterial are stable at 8° and less and do exist at inclinationsin excess of 12°, though they are then always unstable. TheVaiont landslide (p. 67) was a reactivation of a Post-glacial(nor pre-glacial) landslide. Failure surfaces having a mini­mum factor of safety are frequently non-circular, rather thancircular (p. 68). The term flow slide is used far too widely(p. 68) to cover not only liquefaction slides but also rockavalanches or sturzstroms. Fluidization is confused withmomentum transfer. In the earthquake-induced landslide atTurnagain Heights, Alaska (p. 69), movements are believedto have been initiated by the liquefaction of lenses of sand.In the discussion of the tip failure at Aberfan, South Wales(p. 69), the importance of the looseness of the end-tippedmine waste is not mentioned and undue weight is givento the presence of tailings within the tip. The role of thesuccessive extensions of the west arm of FolkestoneHarbour in bringing about several of the largest renewals ofmovement in the coastal landslides at Folkestone Warren(p. 72) is made clear, but the relevant dates of extension are1863, 1883 and 1905. The stabilization of landslides bydrainage could have been given more prominence, togetherwith some mention of the associated danger of the clogging

of drains.To some degree, this book is good value for its price of

£9.50, although its price per page is roughly twice that ofsome other student editions of technical texts, and its priceof nearly 60p per reference may be a world record!If accompanied by extensive field excursions, exercises ingeological and geomorphological mapping in conjunctionwith courses in air photo interpretation and wide readingleading to class presentations and intense discussion ofcrucial case records, the present volume might form auseful aide memoire. None of these supporting activities ismentioned, however, and one trembles to think of studentsbeing raised on such sparse fare. The author presents thebreakdown into 'bite-sized sections' as one of the mainstrengths of the book. Your reviewer sees it as a damagingdevelopment, tending to make our undergraduate coursesmore superficial and to encourage those who seek to reducefurther the engineering geological content of civil andmining engineering degrees.

J. N. HUTCHINSONDepartment of Civil Engineering

Imperial College, London

Quaternary of the Thames (Geological ConservationReview Series), edited by D. R. Bridgland, 1994, Chapman& Hall, London, 440 pp. ISBN 0-412-48830-2 (HB),£79.00.

The purpose of the Geological Conservation Review(GCR), the arrangement of GCR volumes, and their price,have already been discussed in the Proceedings (Gray,1990; Powell, 1993) and are not re-examined here. Thisreview concentrates on the scope of this volume and itssignificance for a subject that has always been close to theheart of the GA. Well over a hundred of the 850 referencescome from the pages of the Proceedings. But this is morethan a valuable reference source for important Quaternarysites in the Thames valley. It brings to the subject a newunderstanding, based on recent studies of sedimentologyand geomorphological process, and on a stratigraphy withglobal rather than regional authority. Because the textis largely written by one person, David Bridgland, theimplications of this refreshing approach pervade the wholework.

In global terms, even in European terms, the Thames is acomparatively small river. There must be valleys elsewherein which a more complete record of Quaternary environ­mental change is preserved, but such a record has yet tobe described in the detail that already exists for the Thames.Quaternary studies of the Thames have a scientific import­ance out of all proportion to the size of the river. This ispartly because many stages of development can be recog­nized, from the earliest Quaternary to the present day, butchiefly because the subject has been a lively source of

BOOK REVIEWS 231

debate for over 150 years. The literature on the subject islarge, containing many descriptive and speculative accountsrelating to several different disciplines. The evaluation ofthis material is a particularly challenging task.

There have been many previous attempts to understandthe Quatemary history of the Thames (e.g. Whitaker, 1889;King & Oakley, 1936; Wooldridge, 1938; Wymer, 1968;Gibbard, 1985, 1994) but there are solid reasons whythe present volume should take its place alongside thesedistinguished and influential works of scholarship. Thefoundation of Bridgland's achievement is broad and wellconceived. He places the explanation of valley developmentand terrace formation in a modem geomorphological andsedimentological context. his four-stage model of terracedevelopment is no doubt an oversimplification but much ofthe evidence can be accommodated in it without too muchspecial pleading. His use of the oxygen isotope stratigraphyis a step forward which is long overdue. Within this broadframework of understanding, Bridgland brings together thenumerous strands of evidence. This task is made more thanusually difficult by the long history of investigation, whichextends the scope for ambiguities in the record, for conflictamong the findings of different methodologies, oftenexacerbated by their fiercely partisan adherents, and fordiffering interpretations of weakly founded regional strati­graphies. Some of these problems have been resolvedby new field investigations undertaken by Bridgland andothers as part of the Geological Conservation Review.

Thirty-nine sites are described. Their distribution reflects,in part, broad patterns of erosion and deposition withinthe Thames basin during the Quaternary. There are, forexample, no pre-Anglian sites from the Lower Thames,because the river lay much further north at that time. On theother hand, in the same region, on either side of the estuarywithin a few kilometres of the Dartford Tunnel there areseven post-Anglian GCR sites, reflecting the wealth oforganic and archaeological material preserved in the fine­grained sediments of the lower reach of the river.

The choice of sites also reflects the history of research.The account of Swanscombe, with its complex stratigraphyand its tantalizing human interest, extends to 25 pages,easily the longest account of a single site. Similarly, Clactonwith a history of investigation extending back to 1838 has17 pages devoted to it. There is also an editorial presence inthe choice of sites. There are no pre-Cromerian sites eitherupstream from the Goring Gap, where at least one site in theNorthern Drift of Oxfordshire might have been included, ordownstream from the Hertfordshire border, in Essex, wherethe Sudbury Formation is extensively preserved. Cromerianand post-Cromerian sites, on the other hand, are well repre­sented in Essex, with twelve sites described in the east ofthe county, where Bridgland is on his home ground. Thereis an understandable editorial dilemma in dealing with thewanderings of the ancestral Thames northward through EastAnglia. That these are not explored here no doubt reflectsthe intended scope of future GCR volumes. The pre­Cromerian Thames will undoubtedly have a place in theQuaternary of East Anglia.

The stratigraphical range of the sites reveals the strengthsand weaknesses of this volume. There are no Holocene sitesincluded and only three sites representing the last majorglobal climatic cycle, from the Ipswichian, through theDevensian to the present day. In a volume where interpret­ation depends to a large extent on a climatically-drivenmodel of terrace formation, this apparent neglect of recentenvironmental change seems rather perverse. On the otherhand, 26 of the 39 sites are of Middle Pleistocene age. Theproblem most effectively dealt with is the relationship ofMiddle Pleistocene terrestrial events to the oxygen isotoperecord - the problem of placing biological evidence andarchaeological materials in their proper stratigraphicsequence and making a re-assessment of Quaternaryecology and implement typology an exciting and worth­while prospect. Bridgland's keen awareness of theseproblems, his understanding of their significance and hismasterly handling of the evidence are everywhere apparent.This a very persuasive account both in the evaluation ofthe individual sites and in the overview that it providesfor the wider region.

REFERENCES

GIBBARD, P. L. 1985. The Pleistocene history of the MiddleThames valley. Cambridge University Press, Cambridge.

-- 1994. The Pleistocene history of the Lower Thames valley.Cambridge University Press, Cambridge.

GRAY,J. M. 1990. Review of: Campbell, S. & D. Q. Bowen. 1989.Quaternary of Wales (Geological Conservation Review), NatureConservancy Council, Peterborough. Proceedings of theGeologists' Association, 101, 355-356.

KING, W. B. R. & OAKLEY, K. P. 1936. The Pleistocene succes­sion in the lower part of the Thames valley. Proceedings of thePrehistoric Society, 2, 52-76.

POWELL, D. 1993. Review of: Treagus, J. E. (ed.). 1992.Caledonian structures in Britain: South of the Midland Valley(Geological Conservation Review 3), Chapman & Hall, London.Proceedings ofthe Geologists' Association, 104,75.

WHITAKER, W. 1889. The geology of London and ofpart of theThames valley. Memoir of the Geological Survey of the UnitedKingdom.

WOOLDRIDGE, S. W. 1938. The glaciation of the London Basinand the evolution of the Lower Thames drainage system.Quarterly Journal of the Geological Society, 94, 627-667.

WYMER, J. J. 1968. Lower Palaeolithic archaeology in Britain:as represented by the Thames valley. John Baker, London.

CHRISTOPHER GREENDepartment of Geography

Royal Holloway College, London

Pleistocene History of the Lower Thames Valley, Philip L.Gibbard, 1994, Cambridge University Press, 229 pp. ISBN0-521-40209-3 (HB), £60.00.

This is a monograph resulting from Philip Gibbard'scontinued research on the Quaternary sequence of the