HISTORICAL DATA USED AS AN INDICATION OF OCEAN LEVELS

Excluding hypothetical tectonic changes as an explanation, particularly where no indication of tilting can be found, the following is an attempt to survey indications of coastal movements consistent with known data since 6000 B.P. For this, the rebound of the Scandinavian landmass after the last glaciation, is taken as real and worldwide eustatic changes of the ocean level are traced.

The present level of the sea designated as O. (Ordnance Data), N.N. (Normal Niveau), N.P. (Normal Pegel) is a normalized height on the surface of the earth, generally the mean height of the sea between high and low water. For surveyors’ purposes, the sea level is defined and marked according to a set of actual measurements. During the last 100 years the sea level rose by some 15 cm; this fact was especially well established from Dutch pegels.

As we are not in a position to estimate the sea level at any time before 1850 exactly, a difference of 30 cm cannot be considered as significant. The more general term “present sea level” will therefore be used here; to this we will relate all indications of “sea level changes” compiled from data relating to historic or pre-historic timesThe “present sea level” seems to have been reached in the 16th century; since that date there have been no indications of any permanent change of an order greater than 30 cm. However, there are definite signs that between 700 A.D. and 1600 A.D. one or more distinct sea level minima occurred (Fig. 4B).

During the 15th and 16th century A.D. (Fig.4A) a general rise in the price of salt all over Europe was the reason for serious political and social unrest (K(LNER, 1920). This links up with the fact that the salt producing broads, meres, clair’s and kogs (KOSTER, 1960), in East Anglia, (CLARKE, 1960, pp. 22,24; KESTNER, 1962, p.469) in Holland, France and Friesland (BANTELMANN, 1960, p.52; BUSCH, 1960, p.128) respectively, were flooded, and peat salt production had to cease.

In Holland , this producti was prohibited by law , because of weakening of the sea defences (DENDERMONDE and DIBBITS, 1956, p.48). Prussia and Livonia became susceptible to salt famine in the late 14th century (TANNER, 1932).

The peat broads and meres are still flooded today, and the extent of these areas indicates that millions of tons of peat were produced when the sea level was at a low. Also the Chersonesus settlements seemed to decay at this time (MONGAIT, 1961, p.189), probably due to the same cause.

Between 700 a 800 A.D. (Fig. 4B) people had moved to the Broadlands area in East Anglia (CLARKE, 1960, p.147) and peat cutting and salt making started.

The Domesday Book records at least 1,200 salt making area (Salinae) (BRIDBURY, 1955, p.19); another indication that the level of the sea must have been lower than today (Fig. 4B).

In the 11th century (Fig. 4B), the isla of Walcheren (BRONSTED, 1960, p.37) boasted a flourishing community; the fact that it was unprotected by dykes during this period (BRIDBURY, 1955, p.4) is indicative that the sea was considerably lower than the present level, even when we take in account that it was probably somewhat protected by natural sandbars.

The area of Haithabu (near Schleswig) flourished during the period of 900 A.D. (Fig. 4B); as the land was 1 m higher above the level of the sea than today, it follows that the sea must have been at a low (K(STER, 1960). Until the 13th century Yarmouth was at least 10 ft. higher above the sea than now (CLARKE, 1960, p.22).

IVES (1803) says that about the time Edward the Confessor (1042-1066) (Fig. 4B) the sea “retreated from the sand of the estuary on which Great Yarmouth now stands. A similar pattern of emergence at that time occurred in L(beck (K(STER, 1960).

The Viking occupied the low lying island on Noirmoutier, on the Atlantic coast of France, an area where at that time the salt pans of Bourgneuf developed (AGATE, 1904, p.5) . At about the same period (860 A.D. Fig.4B) they occupied a similar low island on the mouth of the Rh(ne “Camargue” , an area of salt- making until today. Simultaneously the salterns of the Crimea in the Black Sea were emerging and were likewise occupied by a Viking taskforce, taking the landway (BRONSTED, 1960, pp.55-56).

Ravenna, like Aquileia, became land-locked then (Fig.4B) due to the receding sea, and consequently lost all her salt, fish-salting industries, trade and power to the lower lying Venice. “Fishing and the refining of sea salt were at first the principal resources of the inhabitants of Venice” (PIRENNE, 1958, p. 185).

The salt makers in Friesla began to work in the emerging peat area of the Wadden (tidal flats) and traded intensively with all of northern Europe (Fig.4B) (PIRENNE, 1957, pp. 236-239; HALLAM, 1959-1960; NENQUIN, 1961, p.110).

The salterns of the Pyrenean coast are mentioned in 929 and 978 A.D. under the name of Lima, do Cavado, do Ave, do Rio Leca, do Douro, do Vouga, do Mondego (ELLIS, 1955, p.36) and it is probable that they were flooded for several hundred years before this period (Fig.4B).

The Popes had solar salt pans in the Ostia salt flats, where such activity had ceased after Trajan because of flooding (FEA, 1831).

The fortunes of the salt makers suffered disastrously from the effect of floods which occurred in 1362, A.D. and 1634 A.D. in all Lowlands (BANTELMANN, 1960, p.52). The destructive power of these floods, which invaded the coasts of Europe, seems to have been enhanced by a general rise in the sea level again; this rise can be deduced from the dyke-building activity designed to counteract it in the last 600 years all along the threatened coasts of northern Europe (Fig.4A) (DENDERMONDE and DIBBITS, 1956, p.47; CLARKE, 1960, p.22; KESTNER, 1962, p. 469). The minimum of the sea level of the 11th century (Fig.4B) was preceded by a maximum in the first millennium A.D. (Fig.4C).

It is known that on the East Anglian coa (NENQUIN, 1961, p.136), practically no salt was produced after 425 A.D. (Fig.4C). and hardly any was consumed. The area was almost uninhabited until ca. 700 A.D. (Fig.4B) (CLARKE, 1960, p. 147). Duurstede in Holland had a small population, which lived basically from the fishing and saltfish trade. Only the upper peat bogs in Ireland, the salty sands of the Isle of Man and the oil shales in Dorset made a comparatively high standard of civilization possible.

However, the sea must have already been high at about 100 A.D. (Fig.4D) because of the evidence that in the first half of the 2nd century A.D. (Fig.4C) a port was utilized by Roman merchants in the vicinity of the Norfolk broads now inland (CLARKE, 1960, p. 119). The port of Classis near Ravenna was capable of harbouring 100 ships during the period of the Roman Emperors (Fig.4C), starting shortly after the time of Augustus and it was still busy during the reign of the Gothic kings (GOETZ, 1913, pp.13, 136). BURY (1958, pp.161, 213) quotes in his History of the later Roman Empire that during that period a visitor from Gaul described the Ravenna- Classis area as if it were Venice itself, with its lagoons and canals; in 800 A.D. (Fig.4B) it must have been already several kilometres inland, because the island of Venice was now inhabited (Saint Mark’s relics transferred to the town in 826 A.D.). The port at the mouth of the Tiber were built on progressively higher ground by Claudius and Trajan (Fig.4C).

The Augustan Port near Ostia suffered the loss of 200 ships when Rome was flooded in 62 A.D. (TACITUS, 1829); a catastrophe which led to the construction of Trajan’s port (Fig.4D).

In his article “Observations on the Temple of Serapis Pozzuoli in Naples” BABBAGE (1847) writes of the discovery in the year 1749 of three marble columns, which formed part of a large temple supposedly dedicated to the God Serapis (before 100 B.C.). According to his description these columns were still in an upright position, and throughout part of their height, were perforated in all directions by a species of boring marine animal, Lithophaga (YONGE, 1963). Today the highest of these perforations are 1.80 m above the present sea level. If these columns have really remained vertical all this time, then it is proof that they are “non-tilting”; consequently local earthquakes are not sufficient reason to explain the up and down movements of several metres amplitude.

In the ancient port Caesarea, south of Haifa, stands a wall which must have been built between the time of Herod and the 2nd century. (A. Negev , personal communication , 1962). The tope of this wall, now 1.50 m above the present sea level, is perforated with the typical holes made by the Lithophaga. The wall stands vertical and shows no sign of tilting. Near this wall are the remains of two aqueducts which once supplied Caesarea with water. Of the two, the older one was built near the present shore line; the parallel and newer aquaduct, situated further inland, must have been constructed when the sea was threatening and ultimately destroying the first one (REIFENBERG, 1951, pp. 27-28). It is most probable that the original aqueduct was constructed during Herod’s reign or shortly after, and that it was situated at that time quite far inland. It is estimated that it was destroyed towards the middle of the first millennium A.D. and the sea, therefore, must have been temporarily 1-2 m higher than it is now ((Fig.4C).

Not only are the aquaducts of Caesaria (REIFENBERG, 1951) and the columns at Puteoli still in the original positions of construction (two things which would be almost impossible if there had been a tectonic movements of 3 m vertical amplitude since their erection) but many other old buildings in the reputedly unstable Mediterranean area are still vertical, a sign that the instability in many places was not great enough to cause a tilt. At the old shore the Etang of Vendres, near the mouth of the Aude, are the ruins of a Roman Therme of the 1st or 2nd century A.D. (locally called the temple of Venus). There the walls have been washed out by waves so that they now have a deep double notch about 1.80 m above present sea level (Fig. 4C). The remaining walls of the “temple” are not tilted at all.

Salamis on Cyprus was flooded in 345 A.D. (NEWMAN, 1953, p.65) Tyre was separated from the mainland 380 A.D. (ST. JEROME, 1933). The population of maritime Greece had dwindled in the 2nd century A.D.; trade by-passed it (NILSSON, 1962) (Fig. 4C).

Radiocarbon and pollen analys data have been used for studying sea level changes after the last glaciation, and extensively compared by JELGERSMA (1961).

Unfortunately these methods can only give estimates of within time intervals of several hundred years and differences of heights of half metres at best. Still, it is clear that the sea level at the Frisian coast according to 14C peat determination was higher ((Fig. 4C) in the middle of the first millennium A.D. than it is today and much higher than it was in the first millennium B.C. (Fig. 4F). The maximum in the middle of the first millennium A.D. is also supported by 14C data in the stable Recife area of Brazil (VAN ANDEL and LABOREL, 1964) (Fig. 4D).

Similarly the studies of GODWIN (1943), (archaeological , palynological and ecological) show for the middle of the first millennium A.D. (Fig. 4C) a definite rise of 1 m in the Fenlands of East Anglia over the present day sea level there, and a subsequent fall of several metres below today’s level in the 11th century A.D. (Fig. 4B).

Trajan succeeded in renewing a “Suez Canal” built originally by Ramses II (1230 B.C.) (MUIR, 1924) (Fig. 4D).

In the first half the first millennium A.D. all the areas which were connected with salt trade from inland sources had a peak in their development: the Judean hill towns, Tripolitania (GOODCHILD, 1950) and Asia Minor (NICEPHOR, 1562) (Fig. 4C) a strong indication that the salt pans at the ocean coasts were flooded and unseless-so that the inland salt sources had to be used in spite of more expensive and difficult over land transport.

If one accepts a connection between the melting of the Antarctic ice cap and the small eustatic oscillations of the oceans during the Holocene, then the ice core of “Little America” (Ross ice shelf) deep sounding is significant (BLOCH and HESTER, 1962). It shows an ash layer circa 100 A.D. (Fig. 4D) which indicates a considerable volcanic outbreak at that time (CRARY et al., 1962, p.2806) and a strong albedo change over a wide area of the Antarctic ice mass with consequent increased absorption of solar radiation. This outbreak must have been especially albedo changing , as the methods used up to now for the detection of solids in the ice core have not shown any subsequent ash falls (although it is, e.g., known that the Krakatoa outbreak which occurred in 1883 must have distributed world wide albedo changing ash).

The ocean was several metres below present day level during most of the first millennium B.C. (Fig. 4F). This is indicated by the local results of GODWIN (1943) in the Fenlands of East Anglia as well as by 14C data relating to the Dutch coast where no warping is supposed to have taken place (JELGERSMA, 1961). It would seem that all Greek and Phoenician ports between 700 B.C. and 50 A.D. (Fig. 4F) were built in the sea, or more probably, at a sea level several metres below the present. However, this has to be verified, because no erratic changes of sea level at such ports have ever been taken into consideration, even as a remote possibility (LEHMANN-HARTLEBEN, 1923).

The fact that several fastening devices for ships found in ports of the 1st millennium B.C. (Fig. 4F) were metres below present sea level, has been explained as a tectonic emergence; this applies to those in Petuoli, the Adriatic coast near Triese, Sicily and in Asia Minor. The same explanation is given for the Roman salt pans which were found 3 m below present sea level (Fig. 4F) in excavation at Venice (DE BIZZARO, 1901). All facts are better explained with eustatic sea level oscillations.

About the middle of the first century B.C. (Fig. 4F) the island of Iktin (which was the chief source of supply of tin from the British island to the East) was described by Diodorus Siculus as an island connected by ridge with the mainland, passable at low tide. If DE BEER’S (1960, pp. 161-162) identification of this island is correct, then it follows that the sea was somewhat lower in Diodorus’ time than today.

In the Crimean area, ports and towns which were founded and inhabited from about 500 B.C. to 300 B.C. are now partly under water (Fig. 4F) , and even their defensive walls are inundated (MONGAIT, 1961, p. 199). Thus the Black Sea- like the North Sea, the Atlantic and the Mediterranean- was considerably lower in the middle of the first millennium B.C. (Fig. 4F) than at present.

A short rise of the ocean levels might be indicated for about 400 B.C. (THUKYDIDES) by high salt prices reported for Athens (EHRENBERG, 1951, p. 223), and by the fact that at about that time new positions were selected for salt pans in the Ostia area (MEIGGS, 1960, p. 269).

During 600 B.C. (Fi 4E), however , there is evidence that the Mediterranean in Marseilles was almost at the same level as it is now (DIOL(, 1954, p. 285). At this time intensive colonization of the Mediterranean coasts by maritime people (Phoenicians, Helenes, Etruscans) started. The Judean hill towns, on the other hand, underwent and extremely difficult period.

Between 1200 and 7 B.C. (Fig. 4C) we have evidence of an high sea level: Ramses II succeeded in connecting the Niles to the Red Sea by a canal (1200 B.C.) (Fig. 4G) (MUIR, 1924) which re-used later by Trajan and still later by the Arabs, as mentioned before (650 A.D.) (Fig. 4C).

In Schleswig (Haitabu area) a cutba river is indicative of a sudden rise of the sea level (1000 B.C.) (Fig. 4G) (K(STER, 1960).

At the Brazilian coast, a maximum was found for 900 B.C. 14C dating (Fig. 4G) (VAN ANDEL, 1964).

Two ash layers, corresponding to period between 1700 and 600 B.C. (Fig. 4G) were found in the “Little America” core (CRARY et al., 1962, p. 2806). They should have caused a considerable rise of the ocean level.

That the sea level was high in 1200-700 B.C. (Fig. 4G) can be deduced from the sudden decline of the Mycenaean civilization, the emergence of the sea-faring people in the Syrian and Egyptian areas, and the growing importance of the towns of the Judean hills, especially those on the watershed between the Dead Sea and the Mediterranean, as they were the main centres for feeding , sheltering, taxing and probably controlling the salt caravans. These salt caravans had a growing importance when less and less salt could be obtained from the flooded ocean coast salterns.

An error of ca. 250 years is to be reckoned wi concerning the two ash layers in the Antarctic ice core of these times (Fig. 4G) , as an exact dating of their occurrence is impossible at present. Historical data, therefore , might legitimately be preferred for the estimation of sea levels.

The maritime Mycenaean civilization flourished between 1400 and 1200 B.C. This would correspond to a lower sea level (Fig. 4H) than the present one. At the same time the civilization in Jericho declined to an extreme low in 1300 B.C. (ALBRIGHT, 1960, p.99). Salt-making between 1400 and 1200 B.C. was easily possible along the Mediterranean coast if the ocean was low at that time; consequently the salt sources of Jericho were unimportant and neglected then and its civilization declined.

During 170 1550 B.C. (Fig. 4I) the Jordan valley civilization flourished (ALBRIGHT, 1960, p.86-87) whereas the Agean Minoan culture was low; at that time salt had to be brought from Jericho (Dead Sea area) to the coastal plains.

In England the submergence of the 14C dated forest connected with the tin island Iktin (Fig. 4I), indicated a sudden rise of sea level for 1700 B.C. In Brazil (VAN ANDEL, 1964) a maximum is indicated by 14C dating (1700 B.C.) (Fig. 4I) (DE BEER, 1960, pp. 163-164). Before 1700 B.C. (Fig. 4I) the sea, at this same spot, was clearly below present level. In accordance with this, a period of desolation in the Jordan valley ended about this time; this state of affairs had lasted from 2200 to 1800 B.C. Vice versa, the Agean-Minoan coast prospered during this period (Fig. 4K.).

Previous to this, dating becomes even more difficult. We can only guess that early Bronze and Chalcolithic culture oscillated between the sea coast and the desert salt lakes according to the changed of the sea level. However, it is clear that the steep post-glacial overall rise of the ocean (from 30 m below present sea level), which ended about 5000 B.C., must have had a profound influence on the location of emerging agriculture civilizations.