Exploration of the Canal of Xerxes,Northern Greece: the Role ofGeophysical and other Techniques{

R. E. JONES1,* B. S. J. ISSERLIN 2, V. KARASTATHIS 3,S. P. PARAMARINOPOULOS 4, G. E. SYRIDES5, J. UREN6,I. BALATSAS 7, CH. KAPOPOULOS 7, Y. MANIATIS8 AND G. FACORELLIS 8

1Department of Archaeology, University of Glasgow, UK2University of Leeds, UK3National Observatory of Athens, Institute of Geodynamics, Athens, Greece4Department of Geology, Laboratory of Geophysics, University of Patras, Greece5Department of Geology and Physical Geography, Aristotle University of Thessaloniki,Greece6School of Civil Engineering, University of Leeds, UK7Geohme, Patras, Greece8Archaeometry Laboratory, NCSR ‘Demokritos’, Greece

ABSTRACT The Canal reputedly built on the orders of the Persian King Xerxes across a narrow isthmus innorthern Greece to allow his fleet access into the Aegean in advance of the Persian invasion ofGreece in the early fifth century BC must have been a remarkable engineering operation for itstime. Yet apart from a depression in the central sector of the isthmus, almost nothing of thiscanal is visible today, nor are there visible remains of building structures and harbour instal-lations; what information there is about it comes from accounts by ancient writers, notablyHerodotus, and nineteenth century travellers. This paper describes the results of a largeprogramme of survey aimed at detecting this putative, now buried structure and ascertainingwhether or not it was a canal across the full width (2 km) of the isthmus. Following a detailedtopographic survey, resistivity soundings and ground-penetrating radar were carried outprincipally in the central sector of the canal; the latter detected successive infillings of thecanal but neither its original sides nor its bottom. Seismic refraction and reflection measure-ments, on the other hand, provided decisive evidence for the canal’s existence in the centralsector, with strong support coming from the analysis of sediment cores: its depth there is14–15 m below the present ground surface, with top and bottom widths of 25–35 and at most20 m respectively. The canal’s northerly course has been defined but less confidently, whereasto the south the picture still appears incomplete. The canal may indeed have been built acrossthe full 2 km, but the alternative hypothesis that it connected with the sea at only one end andthat there was a (short) slipway at the other end cannot be dismissed. Whichever model iscorrect, a crucial finding from the sediment analysis is that the lifetime of the canal was short.Copyright *c 2000 John Wiley & Sons, Ltd.

Key words: geophysical survey; Xerxes; canal; Greece; ground-penetrating radar; seismics;coring; sediment analysis; radiocarbon dating

Received 13 August 1999Copyright # 2000 John Wiley & Sons, Ltd. Accepted 20 September 1999

Archaeological ProspectionArchaeol. Prospect. 7, 147±170 (2000)

*Correspondence to: Dr R. Jones, Department of Archaeology Gregory Building, University of Glasgow, Lilybank Gardens,Glasgow G12 8QQ. Email: r.jones@archaeology.gla.ac.uk

{The first six named authors of this paper are the main authors and are placed alphabetically with the exception of the co-ordinator, R. E. Jones

Introduction

In advance of the Persian invasion of Greece in480 BC King Xerxes led his forces from westernAnatolia over bridges he had ordered to beconstructed across the Hellespont and into theAegean. His fleet then reputedly passed througha canal constructed across the narrowest point ofthe Mount Athos peninsula in northern Greece(Figure 1) in order to avoid the treacherousconditions around the head of this peninsula thathad earlier (in 492 BC) destroyed the Persian fleet.

From the account of the ancient historian,Herodotus (Histories, Vol. VII, pp. 22±24, 37, 122),the canal's main features may be identified: itapparently had a length of ca. 2.2±2.3 km (twelvestadia), a width of not less than 30 m, sufficient toallow two triremes to pass side by side, and somesections of it, built by Phoenicians, would have

had sloping sides giving a depth of perhaps ca. 4m. Another Greek writer, Philostratos, the Athe-nian of the third to second century BC, wrote ofXerxes' `cut section' across Athos (Berwick, 1809;The Life of Apollonius of Tyana, Vol. XXV). There isnot unanimity, however, that it was a canal in itsentire length; according to Herodotus (Vol. VII,p. 24) the ships could have been dragged acrossthe isthmus ( just as the Romans constructed aslipway (diolkos) across the isthmus at Corinth),and another classical writer, Demetrius Skepsius,claimed that `as far as ten stadia the ground isdeep-soiled and can be dug, and in fact a canalone plethrum in width has been dug, yet afterthat it is a flat rock, almost a stadium in length,which is too high and broad to admit of beingquarried out through the whole of the distance asfar as the sea; at one end the canal did not meetthe sea' (Strabo's Geography, Vol. VII, fr 35). From

Figure 1. Map of the Aegean Sea showing the location of the Canal of Xerxes in northern Greece.

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Figure 2. Estimated course of the canal of Xerxes (in heavy dashed line).

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the early eleventh century AD the area was knownas Prevalakas or Provolakas, meaning diolkos(Lemerle et al, 1970). Further information hasbeen provided by travellers, such as Col. W. M.Leake, (1835), Lieutenant T. Spratt (1847),M.G.A.P. de Choiseul-Gouffier and others, whovisited the canal during the last two centuriesand recorded what they saw; de Choiseul-Gouffier (1809, p. 150) also estimated the volumeof earth required in the canal's construction(ca. 250,000 m3).

Today, beginning at its northern end by thevillage of Nea Roda, the presumed course of thecanal (Figure 2) passes from the sea across an areaof open flat land, that had in Leake and Spratt'stime been a lagoon, to the central sector, which inparts resembles a large natural depression but isnot entirely straight (Isserlin, 1991) (Figure 3). Atthe southern end towards Tripiti, some 250 mfrom the sea, a torrent bed appears to dissect thecanal transversally, and this stream passes be-tween two hills by the present-day seashore,draining into a pool separated from the sea by agravel barrier.

One striking feature of the canal is the apparentabsence of visible remains of features that wouldsurely have accompanied the building and

operating of what arguably must have been oneof the most remarkable civil engineering feats ofthe ancient world. Surface indications of spoilheaps, harbour installations, breakwaters, build-ings associated with the running of the canal,workers' dwellings and so on are not evidenteither on the present ground surface (Isserlin,1991) or on an (Greek Air Force) air photographof October 1989 (but see later section). In sum,then, we can suppose the canal was buried inantiquity under sediment, the canal's only vest-iges today being a broad depression along thecentral sector. The general vicinity of the canal isof considerable current archaeological interest:ancient Acanthus lies to the north, close topresent-day Ierissos, ancient Sani probably liesto the south, the fortification walls of ancientOuranoupolis, founded in the late fourth centuryBC, encompassed the canal (Papangelos, 1993),there is an Archaic sanctuary a few kilometres tothe northwest (Blackman, 1997, pp. 69±70; Tsi-garida, 1990±95), Roman finds occur close tothe southern end of the canal (observed in 1991 inthe section of boreholes 1 m below the groundsurface), and Byzantine structures are to be foundon the prominent hillock at Tripiti southern hill.

Figure 3. The central sector of the Canal appearing as a depression (in which the trees are growing) aligned parallel withthe modern road.

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Responding to the many issues arising fromprevious work at this enigmatic structure, one ofus, BSJI, initiated and has directed a new pro-gramme of exploration at the canal, consisting todate of a number of brief seasons between 1991and 1996 of geophysical and topographic surveysand borehole drilling. An account of the state ofknowledge about the canal prior to the presentproject is given by Isserlin (1991), and Isserlinet al. (1994, 1996) present the results, for anarchaeological readership, of the topographic andgeophysical surveys up to and including 1994;finally, the findings from the seismic surveyalong one profile in the central sector have beenpublished by Karastathis and Papamarinopoulos(1997). Another of us, JU, prepared a preliminaryreport on the second series of VK's seismicmeasurements, the results of which are reportedfully here.

The canal presents a most unusual challenge toarchaeological geophysics, and as such theresults of geophysical survey deserve to bepresented more fully. The purpose of this paperis to treat the multifaceted survey as a geoarch-aeological case study, considering firstly howdifferent geophysical techniques have respondedto the target and secondly what interpretationhas emerged from integrating the geophysicalsurvey data and analysis of sediments from bore-hole cores. We note that this integrated approachis finding increasing application in archaeologicalexploration in Greece and nearby (e.g. Avdera:Syrides, 1996; Psilovikos & Syrides, 1997; Eretria:Kambouroglou, 1989; Troy: Rapp and Gifford,1982; Kayan, 1991); furthermore, it is relevant tonote the use of seismic refraction survey andelectric resistivity profiling combined with litho-logical data collection in the Nile Delta, whichsuccessfully located channels in the eastern partof the delta that are described by Herodotus andother ancient writers and have silted up sinceantiquity (el-Gamili and Shaaban, 1988).

Topographic and geologicalconsiderations

The topographic survey, undertaken by J. Urenand his team in 1991, formed an essential basis ofthe present study of the canal, firstly identifying

its most likely course on the basis of the line oflowest ground level and secondly drawing atten-tion to the distinction between on the one handthe central sector of the canal in which thedepression is clearly visible and, on the other,its two ends, as explained below. From about6000 three-dimensional readings, which weretaken with a Sokkia Set 4c total station instru-ment, a 1:2000 map was generated; Figure 2indicates its most likely course, and Figure 4shows its elevation above sea level. The maxi-mum elevation is 15.7 m roughly half way alongthe canal, the estimated slopes to the Nea Rodaand Tripiti ends being ca. 1.35 and 1.50% respect-ively. The importance of mapping the elevationsof the gently undulating terrain on either side,but especially on the eastern side, of the centralpart of the canal became apparent in interpretingthe core data.

Sands, silts and alluvium are the principalsurface geological features at the canal; limestoneand granite outcrop to the northwest and gneissto the southeast (Figure 5a). The stratigraphicsequence for the wider area of Nea Roda, shownas a synthetic lithostratigraphic column obtainedby Syrides (1990) from surface prospection andborehole data, consists of layers of frequent sandaccounting for the top 15 m, followed by a 30 mlayer of quartz sands with some admixture ofquartz, granite and gneiss pebbles and cobblesca. 40±50 m thick (Roda Formation), and finallygranite bedrock (Figure 5b). In the area of thecanal, red beds predominate. The canal lies in anactive tectonic area; Ierissos, which was the sceneof the M 7.0 earthquake in 1932, is only 5 kmaway (Maravelakis, 1933; Pavlides and Kilias,1987; Pavlides and Tranos, 1991). The building ofthe road alongside the canal (in 1967), farmingactivity on both sides of the canal, as well as thenatural processes of infilling from primarily rain-washed and secondarily wind-blown sedimentmay all, in different ways, be complicatingfactors. The southern stretch of the canal, fromwhere the modern road crosses the canal toTripiti, is, for certain, complicated by a combina-tion of natural factors Ð a former torrent bedthat joins the course of the canal from thenorth Ð and anthropogenic factors Ð minorRoman finds and the recent building of theLobby music hall. I. Papangelos has suggested

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that this valley is a dissected secondary depositwhich had accumulated since cutting of the canalproper (Isserlin et al, 1994, p. 284), but it seemsthat a stream in the southern stretch has had a

long history: from the late tenth century AD thecanal here was known as `Davripos' stream', thisname perhaps originating from the term evriposmeaning canal (Lefort et al, 1985, pp. 4, 49).

Figure 4. Longitudinal section along possible centreline of the Canal of Xerxes showing elevation above sea-level. Theelevations of profiles A, B, C and D are indicated.

Figure 5. (a) Geological map of the area from Ierissos in the west to the canal in the east, running from Nea Roda to Tripiti(adapted from Syrides, 1990).

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Examination of wells dug along the course of thecanal by local farmers for irrigation revealed awater table (during September 1991) of not lessthan 8 m below ground surface. In recentmemory, that is before the construction of thepresent road in 1967, water is reported to havedrained in the direction of Tripiti along thecentral sector of the canal, where the naturaldepression is today most apparent, perhaps froma spring at roughly the canal's midpoint. Thequestion of sea-level change, which is of directrelevance to the present study, recently has beenaddressed independently by Papangelos andKambouroglou (1993), but as yet only

preliminarily results have been published (seeDiscussion). Before the present project began, oneof us, GES, had observed the existence ofsubmerged beachrocks along the seashore atNea Roda, as well as between Tripiti andDeveliki. This finding should be a clear indicatorof sea-level rise, but such a view should betempered by the area's known tectonic activity.

Geophysical survey

The unusual nature of the archaeological targetwas such that the geophysical survey (Table 1)could not follow an easily prescribed route; anelement of experimentation and a sense of flexi-bility were required at all times, and above allthere was recognition that a combination of com-plementary techniques would be more successfulthan the adoption of a single approach. Thesurvey's strategy evolved in the following way.

(i) Reconnaissance survey to be carried outrelatively quickly and at a coarse resolution.With the knowledge that if a canal had beenbuilt it was cut through sediments and notthrough rock, electrical soundings wereconsidered to be an appropriate startingpoint to assess whether the point of contactbetween the canal's sides and the materialthat had later infilled it could be detected,and also as a reference point for futureanalysis of cores from boreholes. Thus thesoundings formed the basis of the firstseason's work taken along profiles of 60±100 m length placed at right angles to thelikely course of the canal (shown in Figure 6),together with the horizontal mapping usinga gradiometer magnetometer at the northernend of the canal. The main criterion inselecting the profiles for electrical soundings(A±D set out in 1991) was that they shouldform an adequate sampling of the canal'scentral sector. Practical considerationsdictated that they be straight and capableof being cleared of vegetation. Prospection atthe northern end of the canal presented noproblem other than from occasional surface(modern) metal, whereas at the southernend it was constrained by the often thick

Figure 5. (b) Lithostratigraphic sequence recorded in theIerissos–Nea Roda area (adapted from Syrides, 1990).

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vegetation and the nature of the terrain.Ground-penetrating radar (GPR) was usedexperimentally in 1991, and, in the light ofthe results of the electric survey, moresubstantially in 1992.

(ii) The results from (i) encouraged a moredirected survey, deploying seismic tech-niques from 1993 onwards and coring (andassociated radiocarbon dating) in 1993 and1994. The importance of combining thesetwo techniques, in particular calibrating theresults of the latter against the former's moreindicative results, is emphasized.

Reconnaissance survey

ElectricElectrical soundings measurements were taken at5-m intervals using the Schlumberger array alongfour 60-m profiles, marked A, B, C and D inFigure 6. Their locations were selected, in the caseof B, C and D, to give reasonable coverage withinthe central sector of the canal and, in the case ofA, as the most suitable point at which to

investigate the southern end of the canal.Preliminary treatment of the data in the form ofthe apparent resistivity values plotted againstAB/2 indicated, according to the location of fourto six layers, a thin high resistivity top layer,beneath which were two low resistivity layers,followed by a more resistive layer below 10 m.The results were then transformed into geo-electric vertical pseudosections reaching a depthin excess of 30 m, and typically showed a top,well-defined layer about 1±2 m deep of highresistivity (4200 ohm-m) colluvium material,giving way to progressively lower values (20ohm-m) in the thick sand±silt layer. The decreaseis partly associated with the increasing moisturecontent with depth (Plate 1; note the logarithmicvertical scale). Interpretation of the pseudo-sections is not straightforward, partly because itis not possible to correct them for the variabletopography of each profile, and in any caseresemblance between them appears superficial.That there is no clear demarcation of the canal'ssides must be attributed, in the light of lateranalysis of borehole cores at profiles C and D, toan overall similarity in texture and compositionbetween material through which the canal may

Table 1. Details for the reconnaissance survey and the phase B survey

Survey Technique Instrument Details Location inFigure6 Publication

Reconnaissance Resistivity soundings(1991)

AbemTerrameter

Schlumberger 5 minterval; 60 m profiles

A–D Isserlin et al. (1994)

Electrical imaging(1996)

Abem Offset Wenner; 3 mand 5 m spacing

B–D Previouslyunpublished

Magnetometry:total intensity (1996)

Elsec 820 2 m bottle height Grid (80� 40 m)and profiles96/1–96/17

Previouslyunpublished

Magnetometry:fluxgate gradiometer

GeoscanFM36

0.5 and 1 m intervals Areas 1–4 Qualitatively inIsserlin et al. (1994)

GPR (1991 and 1992) GSSI SIR 10 80 and 120 MHzantennae; profiles50–120 m length;Hilbert filter

A–D; 92/1–92/6 Isserlin et al. (1994)

Phase B Seismic reflection andrefraction (1993 and1996)

See text D, 96/1– 96/17 Partly published inKarastathis andPamarinopoulos(1997)

Analysis of cores(1993, 1994)

See text See Table 3 C, D Syrides in Isserlinet al. (1996)

Radiocarbon dating(1994)

See text Sediment samples C, D Maniatis andFacorellis in Isserlinet al. (1996)

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Plate 3. High-resolution seismic re¯ection pro®les at D in wiggle trace presentation (a) (top left), and C in colour plot (c) (top right).High-resolution seismic refraction pro®les at D following velocity analysis (b) (bottom left) and at C (96/12) (d) (bottom right). Notethe similarity between the pro®les obtained by the two methods at C and D respectively.

Copyright # 2000 John Wiley & Sons, Ltd. Archaeol. Prospect., 7, (2000)

Figure 6. Locations of the geophysical surveys. The GT 96 sequence refers to the seismic measurements. Boreholes weresunk at profiles C and D.

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have been cut and its infill, as well as therelatively large sampling interval in the measure-ments. Instead, the distribution of resistivitywould seem to point firstly to subtle featuresrelating to the natural infilling of the canal andsecondly perhaps to more abrupt features associ-ated with relict narrow stream beds. The resis-tivity data lack any further resolving power, andregrettably correlation with the stratigraphicsequence shown later in Figure 11 has thus farproved fruitless.

Experiments were made with electrical imagingin 1996 at profiles B, C and D, with 3 m and 5 melectrode spacings. Generation of the modelresistivity sections from the calculated apparentresistivity pseudosections consistently showed, inagreement with the results above, a shallow lightresistance surface layer, together with a well-defined low resistivity area at a depth of 4±9 mapproximately, situated roughly midway alongthe traverse.

MagnetometryIn 1991 the Geoscan FM36 fluxgate gradiometerwas used to explore four areas. In the two areason the eastern side of the flat land close to NeaRoda that were selected in order to detect thepresence of any building structures away fromthe likely course of the canal, only two magneticanomalies were detected, one probably associ-ated with modern soil dumping, the other withpositive intensity values, of irregular directionand uncertain identity. Modern disturbance ofthe topsoil from whatever agency at location91/3, which was aligned with the probablecourse of the canal, was strongly indicated bythe wide, apparently random values obtained. Bycontrast, location 91/4, where a building struc-ture was suspected from the aerial photograph,was magnetically quiet; this surprising, negativeresult has not yet been checked with the land-owner to ascertain what if anything hadhappened in that field since the aerial photo-graph was taken.

At the northern end of the central sector of thecanal (Figure 6), total intensity measurements(bottle 2 m high) indicated an overall increase inintensity moving from northwest to southeast thecanal's infill thus seems to be associated with lowintensity, a result that accords well with the

observation of a high-resistance top layer beingpresent elsewhere along the central sector.

Ground-penetrating radarScans were taken using a GSSI SIR-10 instrumentwith 80 and 120 MHz monostatic (or bistatic)antennae along all the profiles shown in Figure 6.Their lengths varied from 50 to 120 m accordingto location and ground conditions. It was pre-dicted that the relative dielectric permittivity(RDP) contrast at the interface should provideconditions favouring the use of the method,the infill probably having a higher (RDP) thanthe material into which the canal was cut (RDP inthe range 15±25 units).

Despite the relatively high water table causingattenuation of the radar signal, which proved tobe more problematic than was thought originally,useful results were obtained in the central sector.At C (Plate 2) two main features stand out: (i) amarked discontinuity at 4 m where perhaps the`colluvium' gives way to the main sand/claylayer, and (ii) a slope beginning on the east side ata depth of ca. 2.5 m depth (descending at anangle of ca. 408 to the horizontal) to a final depthof around 9 m. A corresponding slope on thewest side is evident, albeit less clearly. Enhance-ment of the data using the Hilbert transform(Plate 2, top) hints at an intriguing further struc-ture, namely two, possibly three, more slopingfeatures observable on the east side. When thevertical and horizontal dimensions are correctedto a common scale (Figure 7) the relative shallow-ness of these features becomes very apparent. Themost reasonable interpretation of them is thatthey represent successive infillings of a buriedcanal-like structure; these infillings appearnatural although some of them could conceivablyrepresent heaps relating to the time of construc-tion. Whatever their origin, the presence of theseinfillings offers indirect evidence for the existenceof the canal bed.

Elsewhere the picture was less clear because ofthe water table problem; at 92/1 along the trackto the Lobby music hall it was encouraging todiscern a trench-like feature ca. 20 m wide with adepth of 9±10 m, but its position lies off the likelycourse of the canal, by not less than 5 m to thesoutheast and its steep sides hint at something of

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more recent date. Location 92/6 close to the shoreat Nea Roda was not informative.

Phase B survey

Seismic techniquesIn principle, the canal seemed to represent anexcellent target for seismic survey. Overall, fourseismic reflection and eight seismic refractionprofiles were acquired, the positions of which areshown in Figure 6 (GT 96). In the initial invest-igation in the summer of 1993 the purpose of thesurvey, limited to one location (profile D inFigure 6), was to look for any structure that couldindicate the possible existence of the canal. Thesurvey continued in the summer of 1996 on alarger scale to follow this structure over much ofits course, thereby avoiding the possibility oferroneously interpreting a local depressionanomaly as a channel. At the same time, twocross-cutting profiles at the same point over thecanal were made in order to determine its exactcross-section, and an investigation of the Tripitiend of the canal was also made by mapping thebedrock in that area.

The equipment used in the seismic invest-igations was based on an EG&G Geometrics 2401seismograph. The receivers were single MarkProducts geophones of 100 Hz resonantfrequency. The seismic sources used were the

`hammer and plate' in the first survey and the`buffalo gun' in the second. It may be noted thatreflection surveys with an investigation depth ofless than 15 m are very scarce (Birkelo et al, 1987;Miller et al, 1989, 1994), the main reasons beingthe difficulties in acquiring adequate resolutionand separating the signal from the coherentnoise (refractions, ground-roll and air-wave).The ground-roll in the data of such shallowdepths takes up a large part in the seismic recordand interferes with the signal in both time andfrequency domains. In addition, the airwave inthese investigations has large amplitudes and itsvelocity is comparable to that of the first layerwhen that is not saturated. The processing of theseismic reflection data with Seistrix II (InterpexLimited, 1991) and Seismic Unix v.30 (Cohen andStockwell, 1995) succeeded in removing noiseand gave four seismic reflection profiles that canadequately describe the canal (DREFL in the firstperiod, AREFL , BREFL and CREF in the secondperiod). Plate 3 shows two of the four profiles, awiggle trace presentation of DREFL (Plate 3a) anda colour plot of CREFL (Plate 3c).

Seismic refraction lines, which were carried outat the same positions as the seismic reflectionlines, gave very similar results to those obtainedfrom the interpretation of the correspondingreflection profiles (Plate 3b and d). Refractionlines were also carried out at places where the

Figure 7. Several phases of shallow infilling of the canal that are evident in the Hilbert transformed data are indicated in aschematised manner in which the vertical and horizontal scales are uniform.

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canal was expected at depths less than 6 m,which were too shallow for the reflection method.All the refraction profiles were processed by thegeneralized reciprocal method (GRM) (Palmer,1981) except the first one, which was processedby the SIPT algorithm (Haeni et al, 1987). Theresults of the individual profiles are summarizedin Table 2.

In order to check the direction of the canal atprofile C, the refraction profiles 96/11 and 96/12crossed each other at a 308 angle. The equal-depth lines at sea-level (lines 1 and 3 in Figure 8),together with the line connecting the deepestpoints (line 2 in Figure 8) were taken as indicatorsof the canal's direction. Figure 8 resulted from theprocessing of these lines. In some places where

Table 2. Results of seismic survey

Location(Figure 6)

Survey type Length ofprofile (m)

Results

96/2 Refraction 50 Loose, surface layer ca. 3 m above bedrock. Velocity analysis suggestssubsurface interface can be attributed to two materials, possibly bedrock andits erosion product, which appears as a well saturated sediment. Figure 9

96/4(�A)

Refraction 57.6 Very shallow features (Figure 10). The lowest point of the subsurface interfaceoccurs just below present-day sea level and, significantly, seems not tocoincide with the lowest point of the topography, lying some 32.5 m to the east(Figure 10). This latter finding, which is taken up in the Discussion section, isimportant because it may suggest that the route of the canal lay furthereastward than previously thought (Figure 13)

96/8(�B)

Refraction andreflection

46 The depression is incompletely revealed, but its top width may be ca. 20 mand depth 5 m. Maximum depth is 13.5 m and the level of the canal bed withrespect to present day sea-level is ca. ÿ4 m

96/11(�C)

Refraction 73 See text, Figure 8 and Plate 3

96/12(�C)

Refraction andreflection

64 See text, Figure 8 and Plate 3

D Refraction andreflection

See text See text and Plate 3

96/16 Refraction 142 Profile is difficult to interpret: shallow depressions are observed at 130–156 mand 76–110 m (Figure 9).

96/17 Refraction 60 A small depression at 40–60 m, possibly a modern stream

Figure 8. The refraction profiles at C. The direction of the canal can be determined by the equal-depth lines at sea level(0 m, indicators 1 and 3), as well as the line connecting the deeper points of the canal (ÿ4 m, indicator 2).

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the surface was inclined over the canal area, thelower point of the surface did not match with thelower point of the canal.

Combining the results of the seismic profilesalong the central sector of the canal, the followingconclusions can be put forward:

(i) the width of the canal at its top is about26±30 m;

(ii) the perpendicular distance between thetop and the bottom of the canal is about5.5±7.5 m;

(iii) the sides of the canal slope at anglesbetween 208 and 308, the shallower slopebeing on the west side;

(iv) the bottom of the canal is estimated to havean absolute elevation of ÿ4 m, but in someplaces it is shallower;

(v) the width of the bottom side was less thanhalf of the top side.

The appearance of the canal section in theseismograms differs with respect to the relativeheights of the east and west sides of the canal. Forinstance, at B and C (Plate 3c) the west side risesand then appears to level off horizontally, incontrast to the east side which rises continuously.This phenomenon, which also is observed in thecorresponding GPR data (Figure 7), is probablythe result of different geomorphological pro-cesses operating on either side of the canal sinceits construction, i.e. greater sedimentation hasoccurred on the east than on the west side.

The results are less clear-cut at the two ends ofthe canal (Figure 9). At Tripiti, on the one hand,there is nothing to indicate a deep canal, but onthe other hand the results are not incompatiblewith the building of a canal-like structure withsides that have since collapsed and which hassilted up (Figure 9: 96/2); a little further inland,at 96/4, there is a somewhat clearer depression

appearing at ca. 30±40 m across the traverse(Figure 10). In the marshy area at the Nea Rodaend, of the two depressions observed in the data,the westerly one looks the more likely to be thecourse of the canal (Figure 9: 96/16).

Analysis of cores at C and DTwo boreholes, G1 and G2, were drilled on theaxis of D and C traverses respectively (by Mr N.Nezis of Technodrill) (Table 3). Several metres ofcore were recovered from both boreholes, andstored in boxes in the mayor's office in Nea Roda.For sampling purposes the core cylinders weresplit down their central axis. Owing to their highwater content, the cores required slow dryingover a period of almost 10 weeks in order toavoid shrinkage, cracking as well as structuraland textural distortion. After drying, the halvesof the cores were transported for further analysisto the Laboratory of Geology and Palaeontology,Thessaloniki University. The remainder of thecores are retained at Nea Roda.

Detailed macroscopic observation in conjunc-tion with the field description of the cores enabledconstruction of lithological columns for the bore-holes (Table 4). Texture and structure of thesediments were also described. Representativesamples of the cores were analysed using sedi-mentological and palaeontological techniques.Two techniques were used to determine particle-size distribution.

(i) Sieving in a 16-sieve nest (with aperturesizes ranging from 5.0 to 0.032 mm) for thesandy samples.

(ii) Pipette method, using sedimentation glasscylinders, for the muddy samples.

A combination of both techniques was followedfor samples consisting of both muddy and sandyfractions. Plotting the results of each sampleon probability paper, cumulative curves were

Table 3. Details of the coring at C and D

Core Corer Elevation (m) Depth (m) 14C samples

C (G2 in Isserlin et al, 1996) 10 cm diameter for top 8.40 m,otherwise 8 cm diameter

ca. 10.70 20.50 13.15 and 13.55 m

D (G1 in Isserlin et al, 1996) 10 cm diameter for top 15 m,otherwise 8 cm diameter

ca. 13.30 24.30 14.10 and 14.20–14.35 m

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formed from which the sedimentological para-meters of mean size (M), sorting (s), skewness(Sk) and kurtosis (Ku) were calculated. Theprevailing sand fraction of each sample wasexamined under a binocular stereomicroscope,and the morphology (sphericity, roundness) ofthe quartz grains (10 grains) was estimatedaccording to the Krumbein and Sloss (hereafter

KS) optical scale. Using a microscope the miner-alogical composition was also determined foreach sample giving the prevailing sand fraction aswell as the coarser and finer fractions.

Four bulk sediment samples were taken forradiocarbon dating by Y. Maniatis andG. Facorellis at the Laboratory of Archaeometryat the National Centre for Scientific Research

Figure 9. Seismic refraction profiles at 96-2 and 96-16. The upper lines mark the ground surface together with thegeophone positions. The dark and grey circles indicate the west and east ends of the traverses respectively.

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`Demokritos' in Athens, as indicated in Table 5.They were taken from levels at a height just abovethe bottom of the canal, as indicated by theresults presented below.

Two groups, A and B, can be distinguished inboth cores on the basis of predominating colour,texture and composition of the sediments(Figure 11 and Table 4). In both cores the contactbetween the sediments of groups A and B occur atca. 14.70 m depth, but it has to be rememberedthat the ground level in core C is lower than incore D and thus group A sediments reach deeperin core C than in core D. The 14.7 m interfacecorresponds to a depth below present groundlevel of 10.5 m and 12.5 m at C and D respectively.The group B sediments, which are more compactthan those of group A, can be described as redbeds, and represent older sediments.

Palaeontological analysis of macrofossils(molluscs and bones) and microfossils (Forami-nifera and ostracods) was carried out on the sandfractions (2.00±0.064 mm) of sediments mainlyfrom the lower part of group A, with the purposeof locating marine indicators. In the event, nonewere found. Instead, in core D, there were twofragments of small bones, one of them possiblyfrom a frog, at 14.65 m, three small carbonisedplant remains (carbonised leaves that resembleolive tree leaves) at 14.60 m, and several smallcarbonised plant fragments and very poorlypreserved insect remains between 14.00 and14.60 m. A small pottery sherd was encounteredat 8.40±8.60 m in core C.

Turning to a comparison between the cores,their content is broadly similar, as is the differ-entiation of the sediments into two groups, A andB, but, as is discussed below, the sediments incore C are more sandy than those in core D. Inboth cores the sediments of group B represent the`natural' sediment into which a depression, prob-ably the canal, was created.

The sedimentological analysis of the sedimentsof group B in both cores reveals silty clayeycoarse sands with subangular pebbles. The sedi-mentological parameters reveal immature sedi-ments (poor sorting, platykurtic) and very lowroundness (0.1±0.3 on the KS scale) of quartzgrains. These sediments, which have a red-browncolour, can be described by the geological term`red beds', surface exposures of which occur inthe wider area around the canal (Syrides, 1990).

The sediments of group A in both coresrepresent the infilling of the depression. Thisfilled up gradually, with loose clastic sedimentsoutcropping in the vicinity of the depression, thatis, from the immediate slopes or surroundingland. In view of the similarity in sedimentologicalparameters (sphericity, roundness and mineralcomposition) of the sediments in the two groups,it seems likely that group A sediments derivedfrom the red beds. Slope collapse and the effectsof rain water must be the main factors that led tothe gradual infilling of the depression.

Turning to the contrast in core compositions,the majority of group A sediments in core D arecomposed of dark brown-blackish fine-grained

Figure 10. Cross-section of the canal at 96/4.

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sediments, whereas in core C coarse sandspredominate. In core D thin lamination is veryclear and well developed, but massive beddingpredominates in core C. These differences,significant though they are, are not fundamental.The deposition of group A sediments in core Dseem to have taken place in a stillwater environ-ment with organic matter present, suggestingperhaps a marsh. Its rate of deposition was low,but there were probably periods of more rapiddeposition giving rise to the coarser material. Thereverse may be the case at core C, where thesediments indicate rapid deposition of coarsematerial but with some intervals when fine-grained material was deposited. These differ-ences in the group A sediments should beexpected in an extensive depression such as a

canal: natural processes, such as side collapseand torrential discharge cause non-uniformblocking and the creation along the canal ofsuccessive small ponds and sediment `fans'.Where such ponds are situated (e.g. at core D),deposition of mainly fine-grained sediments in astillwater environment occurs, but in the `fans'(e.g. at core C) the material is coarse, representinghigh-energy depositional processes. Looking atthe topography of the eastern side of the canal,the location of core C will have received sedimentdirectly from the small depression lying betweentwo prominent hillocks, a situation that wouldhave been much less marked around core D.

Regarding the radiocarbon dates, the firstpoint to note is the large difference betweenthose obtained from the two cores. It must be

Table 4. Characteristics of cores C and D

Characteristics Core C Core D

Mean mineralogical composition of the sanda:quartz 60–70% 60–70%feldspar 25–35% 30%femic minerals 2–5% 1–5%

Surface morphology ofquartz grains

Very angular(0.1–0.3 on the KS scale)

Very angular

Characteristics of group A Grey-brown to dark brown-blackish massive siltycoarse sands with scattered small pebbles. Atsome horizons (1.20–6.40–6.60, 13.00–13.50) thepresence of organic matter gives a blackish colourto the sediments, indicating deposition in a non-oxidizing, aquatic environment, but the bulk ofmaterial in these sediments is composed ofmassive coarse sands with varying proportions ofsilt and clay

Dark grey, grey-brown, silty-clayeysands alternating with silty clays.Fine laminations in the lowermostpart. Deposition in non-oxidising,stillwater, marshy(?) environment

Characteristics of group B Brown-reddish coarse silty sands with varyingproportions of clay and scattered small pebbles.More compact sediments than in A

Red-brown coarse silty sands withvarying proportions of clay andscattered small pebbles

aIn both cores mica minerals increase up to 30% in the fine-grained sediments, as well as in the finer grain fractions ofcoarse sediments.

Table 5. Carbon 14 dates of sedimentsa

Laboratorycode number

Sample Type Percentagemodern

Age BP Calibratedage (1 SD)

DEM-427 D1 (14.10–14.20 m) Sediment 55.83 4682+49 3509–3370 BC

DEM-426 D2 (14.20–14.35 m) Sediment 54.91 4815+46 3653–3528 BC

DEM-436 C1 (13.15–13.35 m) Sediment 29.9 9698+185 9057–8526 BC

DEM-425 C2 (13.15–13.35 m) Sediment (differentchemical treatment)

30.00 9670+90 9019–8639 BC

aThe d13C values were not measured but the standard value of ÿ25% for plant material was used in the calculationsthroughout. References for datasets used: M. Stuiver and G. W. Pearson, Radiocarbon 35 (1993): 1±23, and B. Kromer andB. Becker, Radiocarbon 35 (1993): 125±135. The program used for calibration was: Radiocarbon Calibration Program Rev 3.0,Quarternary Isotope Laboratory, University of Washington (M. Stuiver and P. J. Reimer, Radiocarbon 35 (1993): 215±230).

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Figure 11. The lithological reconstructions of the boreholes from C (right) and D (left).

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noted that dates of sediments are always olderthan the true ages of sedimentation because thesediments contain organic components fromolder carbon present in the soil before sedimen-tation starts. It has been estimated that this effectis dominant when the carbon content of asediment is less than 3% (Mook and Waterbolk1985: 27±31), as is the case of the samples fromboth boreholes examined (C: 0.2±0.3% and D:0.4±0.6%). Why is there a big difference? Theolder date for core C must indicate either muchinfilling of `older' sediment from the slopes ormuch mixing of Group B redbed with the firstinfill of Group A. The latter seems less likelybecause of the well-defined layers at the interfaceof Groups A and B. It has already been notedthat core C lies between two hillocks on thesouth side, and therefore is receiving sedimentfrom both hillocks, whereas at core D thesituation is more conducive to slow rates of infill(coarser sediments in core C represent rapiddeposition of sediments whereas fine sedimentsin core D represent a deposition in a still waterslow environment).

In short, the C14 dates are telling us the relativedifferences in the rate and nature of sedimentinfill, and little more. For archaeologically usefuldates to be forthcoming would require a verylarge programme of C14 dating which cannot atpresent be anticipated (cf. the work at ancientHelike by Maniatis et al, 1995). On the basis of thedates of D1 and D2 one can tentatively calculatethe sedimentation rate at this position to be 12.5cm in 151 years or 0.083 cm/yr. This is a veryslow rate, indicating perhaps a lagoon site whichhas levelled off. Given that the shift to older agesof sediments that contain small amounts ofcarbon may be as large as 3000 years (Maniatiset al, 1995), the true age of the samples from coreD could range from around 6000 BC, representingthe old Holocene undisturbed sediments of thearea, to around 500 BC which is much closer tothe supposed date of construction of the Canaland implies a disturbed situation together withhuman intervention.

Two further boreholes were drilled in 1998, oneca. 162 m southwest of C, the other ca. 450northeast of D, both of them along the apparentcourse of the canal, the former taking account ofthe geophysical data.

Discussion

Exploration of the Canal of Xerxes has been amore complex exercise than was suspected origin-ally. The construction of the canal itself was theoutcome of a remarkable feat of engineering, but itwas, and was surely planned to be, essentially arather simple feature structurally. That relativesimplicity has been confused by subsequentcombination of individual factors, both naturaland anthropogenic, which have exerted theireffects on the canal in diverse ways since it wentout of use. The history of the land on which thecanal was built has been anything but straightfor-ward since the fifth century BC.

At the outset of the discussion of the geoarch-aeological data, which is divided into three sec-tions, it is necessary to recognize that there is aclear ranking in the level to which the differenttechniques have contributed to the central ques-tions posed by this study. The seismic survey andanalysis of cores from boreholes have been themost productive, whereas GPR, magnetics andelectrical soundings have been relatively lessinformative. Despite the apparent primacy ofthe seismic technique two limitations should beidentified. One is the nature of the terrain, whichdictated the direction in which the profiles werelaid out. Although the intention was that theseprofiles would be estimated to run at right anglesto the projected course of the canal, this was notalways achieved, with the result that the appear-ance of the `depression' corresponding to thecanal in some of the seismograms (e.g. 96/2,96/11 and 96/12) may be distorted, if notseriously. The other limitation is the level ofresolution that can be expected. Although theperformance of the technique and the associatedtreatment of the data are classed as high resolu-tion, the depth estimate is no better than 1 m, andas such the interpretation of the seismograms atan archaeological level needs to be kept inperspective. Inspection of the seismograms atthe two ends of the canal (see later) bears out thatpoint: here the depressions are so slight that theirassociation with the canal is potentially ambig-uous. No more than the general features of thecanal are discernible and even these involvesubjective estimations of the top and bottomwidths (and thus the depth of water in the canal)

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and the depth of the canal below present-dayground level. Nevertheless, we remain confidentof the validity of the interpretations presentedbelow.

Central sector

The most readily interpretable geophysicalresults have come, perhaps not surprisingly,from the central sector of the canal, from seismicand to a lesser extent GPR survey. Here, at C andD, a buried feature is found that may be either anatural depression or a canal infilled by sedi-ments; the feature seems to be buried belowpresent ground level to a depth of 6±8 maccording to the seismic data at D, but estimatedby GPR to be ca. 4 m at C. This discrepancy in thedepth measurement is unlikely to be real, prob-ably being attributable to the limits of resolutionof the two techniques, as well as the differentattributes of the sediments they are measuring.As explained in a previous section, GPR seems tobe detecting some of the successive phases ofinfilling, in a manner that apparently is totallyabsent in the corresponding seismic data. At Dthe maximum depth is 14±15 m from the groundsurface and the feature's top and bottom widthsare 25±35 m and at most 20 m respectively. Amost significant result emerging from the seismo-grams at B, C and to a lesser extent at D, is thatthe centre point of the canal seems to divergefrom that estimated originally in Figure 2, lying afew metres eastward (Figure 10). This point istaken up in the next section.

The main features of the central sector of thecanal were identified from interpretation of theseismic data in an earlier section. Although theindications are that these characteristics need nothave been entirely uniform along the course ofthe canal (see below), it is at least helpful to showwhat a typical section might have looked like;Figure 12a shows a proposed reconstruction at D,which compares well with that put forward by deChoiseul-Gouffier (1809) (Figure 12b).

There is good correlation between the seismicand sedimentological data. Boreholes at C and Dpenetrate two groups of sediments, A (0±14.70 mat D and 0±14.60 m at C) representing infill of adepression, and B (14.70±24.30 at D and 14.80±

20.50 m at C) being the `natural' sediments inwhich the depression was created. It seems veryreasonable to equate this depression with thecanal. The level of correlation between the twodata sets extends to the estimation of the level ofthe base of the canal with respect to existingsea-level: at C it is ca. ÿ4 m, whereas it is muchless, ca. ÿ1±2 m, at D. This discrepancy isdiscussed below.

The northern and southern ends

The divergence from the originally estimatedcourse of the canal, noted above, becomes morepronounced at profile A (96/4). The depression ispoorly characterized, but it is the case that thelowest point of the subsurface interface occurswell to the east (ca. 32.5 m east) of the lowestpoint of the topography (Figure 10). The situationis less clear at the shore at Tripiti (96/2), wherethere is a hint only of a broad depression at theeastern end of the profile, with that at the westernend (i.e. A) being associated with the present-daypool. Superficially, the position of the formeraccords well with the result at 96/4.

At the other end of the canal, of the threeweakly defined depressions observed in 96/16the easterly one matches with the present-daystream bed, leaving the westerly one as a candi-date for the canal itself; encouragingly, that at ca.80±100 m lies close to the estimated line of thecanal (Figure 2). Little can be said of the resultfrom 96/17 close to the coastline, where thetechnique was operating at its limit in respect ofthe shallow depth of the target.

Summary

There are two alternative models. Model 1 isbased on the coring evidence showing an absenceof marine indicators in the sediments.

(i) The canal traversed the complete isthmusand was dug below the prevailing sea-level,but it remained open for such a limited timethat no marine organisms developed tosubsequently leave shells detectable in sizeand number with ordinary palaeontologicaltechniques. There was a rapid blocking ofthe canal as a result of the sides collapsing

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and the formation of marshes. Its deteriora-tion would have been particularly rapid atthe Tripiti end, where the small valley exitsto the sea between two prominent hillocks.

(ii) The issue of the relative levels of land andsea during the first millennium BC, whichhas already been mentioned, is a complexone. Papageorgiou et al. (1996) havetabulated information from archaeologicalaccounts relevant to the sixth and latercenturies BC of coastal sites in Macedoniaand Thrace; estimates of submergence rangefrom at least 2 m at sixth to fourth centuryBC Limenas on Thasos to possibly 1 m at aClassical `molos' at Ierissos. Based onobservations of the ancient shorelines andpositions of beachrock at 61 coastal sitesthroughout the Chalkidiki (including NeaRoda, Tripiti and Ierissos), Papangelos andKambouroglou (1999) report a greaterchange in relative sea-level: ca. 2.5 m sincethe fifth century BC (see also Kambouroglou,1991). In the beachrock at Nea Roda,

submerged to a depth of ca. 2.3 m belowsea-level, they found some pottery which,they argued, dated the ancient coastline tobefore the fourth century BC. Elsewhere inthe Chalkidiki, a figure of ca. 1.75 m hasbeen estimated recently at Torone on theadjacent peninsula of the Chalkidiki, thisrise being attributable probably to tectonic/seismic action as much as to eustatic sea-level rise (Blackman, 1998, p. 80). Turning tothe Mediterranean, Blackman's account(1973) of the evidence of sea-level changein ancient harbours and coastal installationsaround the Mediterranean serves to empha-size the point that generalizations aredifficult to make, each site needing to beconsidered on its own merits. We note thatthe entrance channel to the sixth to fifthcentury BC Punic harbour (or `cothon') atMotya in Sicily has been subject to a relativerise of probably 1 m (Blackman, 1973, p. 132;contra Macnamara, 1974), the quaysideabove sea-level and the depth of water in

Figure 12. Representations of the canal section at D (a) based on the seismic data and (b) according de Choiseul-Gouffier(Isserlin et al, 1996, figure 1c).

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the channel both being ca. 1 m. In thecomparable harbour at Carthage, the depthof water may have been 1.5±1.8 m, therelative rise in sea-level being estimated at0.70±1.0 m (Hurst and Stager, 1978).

(iii) Working with a figure of 2 m rise since thecanal's construction does have seriousimplications for the working model of thecanal because it would mean that at D thecanal was not deep enough for the sea toenter, and at B and C it was (dangerously)shallow (ca. 1 m). There are, however, somemitigating circumstances and factors that canbe brought to bear: (1) the rise in sea level hasin fact been less than predicted, (2) its effectshave to some extent been counteracted bytectonic changes that have, for example,caused relative uplift of the central sector,and by implication consequent depression atone or both ends, (3) the distinction betweenthe A and B sediments in the cores is indeedreal but does not for some reason representfaithfully the canal bottom, and (4) the coringat C may not have penetrated the maximumdepth to the canal bed but instead is situatedslightly to one side.

(iv) The geophysical data accommodate thismodel for the length of the canal with theexception of the southern section fromprofile A (96/4) to Tripiti (96/2), where theevidence is equivocal. The data, however,do hint that the southern sector of the canalwas not straight, instead curving eastward(Figure 13; see also Figure 10) and perhapsfollowing the lower slopes of the present-dayhill to Tripiti rather than the lowest line ofthe topography taken today by the streamleading to the pool by the shore. As a con-sequence of hurried construction and accept-ing the argument that the canal was not builtas a lasting monument, the canal may nothave had a uniform appearance; there couldhave been unevenness in its depth and sides,as well as other imperfections of which weare unaware.

Model 2 relies on the geophysical, especially theseismic, data.

(i) Notwithstanding the difficulties just pre-sented regarding the sea level at the time

of construction, the canal ran from the shore-line at Nea Roda at least as far as 96/8. Thedimensions of this canal were fairly constantand moreover were suited to its purpose andfunction: 30 m top width, 20 m bottomwidth, depth of water 3m.

(ii) The topography of the stretch from around96/4 to the sea at Tripiti, however, did notcomfortably allow a continuation of thecanal of those same dimensions: this stretchwas too narrow to accommodate such acanal. Instead there was a short stretch ofslipway (diolkos) along which the ships weredragged to where the canal proper began. Thecanal had thus only one direct connectionwith the sea. The diolkos was probablynarrower than the canal itself, and wouldhave been simple in construction: a shallow,unpaved depression. In this model, detec-tion of the diolkos by geophysical meanswould be very difficult because of lack ofcontrast between its interface and its sur-rounds: this is indeed an impression gainedfrom interpretation of the seismic data from96/2 and 96/4.

(iii) This model is in harmony with DemetriosSkepsius' view (see Introduction) that acanal could not be dug into a section of`flat rock' almost one stade in length.Although this `flat rock' cannot be relatedto today's local topography (Isserlin, 1991,p. 87), it is tempting to equate this sectionwith the Tripiti end of the isthmus, despitethe fact that at the time Demetrios Skepsiusgained this information about the canal therewould surely have been some form ofdepression occurring between the tworocky hills observed today at Tripiti; whetherthis section was canal or diolkos, it wouldhave long since been covered with slope-wash.

(iv) Casson (1926, p. 29, note 2) records that inthe early nineteenth century during the Warof Independence the depression formed bythe original canal lent itself, no doubtconveniently, to the task of dragging shipsacross the isthmus.

(v) Model 2, which would help explain theabsence of Foraminifera in core C, does notrun counter to the hypothesis that the

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canal's useful lifetime was short. The canalwas not maintained and its sides soon begancollapsing.

Which of the two models is correct cannot yet beelucidated, nor can the possibility be excludedthat neither is fully correct. Finally, almost noth-ing of substance has emerged from the survey,selectively intensive though it has been, to indi-cate the presence of a building or other remainsthat might be associated with the functioning ofthe canal. Whatever might have been at thenorthern end, it has quite possibly long sincedisappeared, any stone buildings having beendismantled and the stone reused elsewhere.Alternatively, as befitted an operation of limitedduration, the buildings reflected their temporarynature, being constructed of materials, such aswood, that may not have left traces.

The remaining work of the present projectcomprises the analysis of two cores drilled at theend of 1998 (see Results section) and, in the field,

a programme of augering at Tripiti (to shed lightspecifically on the validity of Model 2) and atNea Roda (carried out at the end of 1999). It ishoped that the Greek Archaeological Service'sMarine Archaeology ephoreia will explore in 2001the coast line at Nea Roda to investigate system-atically the presence of any harbour installationsand breakwaters. The potential of aerial pho-tography can surely be exploited further than hasbeen the case thus far, for instance exploring theuse of IR false colour images. Beyond that, thehope must be, at some point soon, to excavate asmall section of the central sector of the canal.This will be a challenging exercise in itself, but itsresults will surely be rewarding.

Acknowledgements

We thank the Greek Ministry of Culture forpermission to carry out the work reported here;

Figure 13. The southern course of the canal in model 1, showing the original estimated centre line (- - - - - -) and thealternative possible centre line (- . - . -) suggested from the seismic data (see Figure 10).

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the ephoreia at Thessaloniki, in particular Dr B.Tsigarida, gave considerable practical assistance.We acknowledge the help and support of Ch.Iosifides, Mayor of Nea Roda. We are indebted tothe British School at Athens, the British Acad-emy, The Seven Pillars of Wisdom Trust and theRussell Trust for financial support. The BritishSchool at Athens and its present Director, D. J.Blackman, are thanked for general support andthe latter for discussion as well. We are particu-larly grateful to I. A. Papangelos and Dr E.Kambouroglou for allowing us to refer inadvance of publication to their recent report oftheir own historical and archaeogeomorphologi-cal research into Xerxes Canal. The support of DrC. De Wispelaere, Director of NATO's Science forStability program is acknowledged. Finally, wethank Dr G. Cross for discussion of some of thegeophysical results and Zoe Riba for assistancewith the resistivity soundings survey.

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