THE ORIGIN OF MARINE GEOLOGY A. A. MANTEN Utrecht ( The Netherlands) x (Received April ,51 )4691 INTRODUCTION In our time, there is a growing interest in the history of science. This may be an indica- tion that science is reaching adulthood. It has taken an established and recognized position. Although still strongly striving towards further advances in a near future, science has now learned that only when seen against the background of its history its present position can be understood and its future prospects be assessed. What is true for science in general also holds for the marine geo-sciences. The following pages show a few major lines along which oceanography and, more partic- ularly, the marine geo-sciences have developed. In the selection of subjects and examples, a review of this length necessarily has to be somewhat arbitrary. Moreover, it ends at a stage where the full scope of the marine geo-sciences actually just began. However, if a discussion of developments during the last three-quarters of a century would have also been included, at least an equal amount of pages extra would have been required and the selection would have been even more arbitrary. Nevertheless, it is hoped that this paper will help a little in the understanding of how the scientific disciplines to which this journal is devoted were born. PRE-CLASSICAL TIMES Hebrews The Hebrews were never a maritime nation. This is reflected in the Bible, which contains no very definite notions about the sea. The waters of the sea represented for them a dangerous and ominous power; in the Creation, these were separated from the dry land, it is true, but they still continuously threatened that dry land (cf. Job 38 : 5; Psalms 46 : 3, 93 : 3, 104 : 6). There are indications that the ancient Jews had similar general ideas about the distribution of land and water as the Greeks at the x Postal address: Cortezlaan ,9 Utrecht (The Netherlands). Marine GeoL, 2 )4691( 1-28 2 A.A. MANTEN time of Homer (cf. Job 26 : 10; Psalms 139 : 9; Proverbs 8 : 27). From the expression in Genesis 1 : 9 "Let the waters under the heaven be gathered together into one place" and the passage in the apocryphal book IV Esdras 6 : 42 "Upon the third day thou didst command that the waters should be gathered in the seventh part of the earth, six parts hast thou dried up and kept them", it has been interpreted that the ancient Jews believed that only one-seventh of the earth's surface was covered by the oceans. This was done, e.g., by Columbus, when he tried to prove that the Atlantic was not of any great extent. Egyptians The Egyptians, like the Hebrews, appear to have been antipathetic to everything connevted with the sea. Maritime commerce was almost unknown to them, and their history contains no indications that they made any important discoveries related to the oceans. The ships they employed, for example in the famous southward voyage ordered by Pharaoh Necho II which resulted in the first circumnavigation of Africa, appear to have been manned by Phoenician sailors. snaicineohP In contrast to the Hebrews and Egyptians, the old Phoenicians, Carthaginians and Greeks had many explorers and navigators among them, who generally sailed the seas for commercial purposes. Although they developed their activities mainly in the Meditenanean area, some of their Voyages reached much farther, to the western parts of the Indian Ocean and the eastern parts of the Atlantic Ocean. The Phoenicians sailed the seas long before the Greeks had emerged from a state of barbarism. They a~e supposed to have come from the coasts of the Erythraean Sea (Indian Ocean), but had already settled all over the Mediterranean area before the oldest Greek and Hebrew scriptures were written. In the Atlantic Ocean, outside the Pillars of Heracles, they recognized an ocean with high tides similar to the Ery- thraean Sea. They sailed the Atlantic along the west coasts of Africa and Europe, to and from Gades and other settlements outside the Pillars of Heracles. They discov- ered the Canary Islands and were acquainted with floating gulfweed. It is not certain whether they reached the Sargasso Sea proper, as the gulf weed is frequently driven to east of the westernmost Azores; it is possible that the Phoenicians met the gulf weed somewhere in the Atlantia. Northward from the Pillars of Heracles, the Phoenicians discovered the Cassiterides, which may have been either the Scilly Isles or the islands in Vigo Bay, on the northwest coast of Spain. They went there in search of tin, of which they kept a monopoly by concealing its source from rival nations. Going still further northward, the Phoenicians reached Britain. East of the classical world, they sailed around the southern part of Arabia into the Persian Gulf and along the east coast of Africa. Commerce in pearls was undoubtedly a major stimulus for ravel in that part of the world. Marine Geol., 2 (1964) 1 28 EHT NIGIRO FO ENIRAM YGOLOEG 3 LACISSALC SEMIT Carthaginians The Carthaginians followed in the tracks of their Phoenician ancestors, the Tyrians, as commercial sailors. Unfortunately, as with the Phoenicians, all their historical monuments have been destroyed. It is likely that the Carthaginians really discovered the Sargasso Sea offthe African west coast. From the Greek translation of the Periplus of Hanno, we know that this Carthaginian admiral sailed as far south as the mouth of the Gambia in about 500 B.C. Another Carthaginian sailor, Himilco, undertook a voyage of discovery in the Atlantic Ocean northwest of Europe at about the same time. Greeks In Greek mythology, Oceanus is the son of Uranus (sky) and Ge (earth), the husband of Tethys, and the father of the Oceanids and River gods. In the writings of Homer, we find a reasonable idea of the conception held by the Greeks of his time concerning land and sea. In his works, the earth is represented as a large disk with slightly elevated lo~ppiH g i / ¢ ~r~X ~-~ciA ) ¢~.~ ~ ~. \ ~-~-~ ~r tr s F L rY ~ Fig.l. The world, according to Homer (about 1000 B.C.). (All illustrations in this paper are after J. Murray, ,5981 Rept. Sci. Results Voyage H.M.S. "Challenger", ).05 edges; in the centre of the disk are the Aegean Sea and its archipelagoes. Oceanus is the river which encircles the whole world, beginning at the Pillars of Heracles, bordering the Elysian fields and Hades, and having its sources in the west where the sun sets. The oldest story about Greek navigation is the legendary voyage of the Argo- Marine GeoL, 2 )4691( 1-28 4 A.A. NETNAM nauts; however, this was probably a Phoenician rather than a Greek undertaking, in search of gold. Towards the end of the eighth century B.C., the Greeks began to build larger ships, which enabled them to undertake more distant voyages with less danger. According to Thucydides, the Corinthians were the first to build triremes, and the Samians learned the use of them from the Corinthians as early as 700 B.C. Early in the sixth century B.C., the Greeks developed newer, less mythological views about the ocean. A century later, Herodotus (484-408 B.C.) abandoned specu- lative theories and gave further attention to the obselvation of facts. Although the Greeks should be considered the founders of scientific oceanography, they likely did not undertake oceanic voyages of discovery before the fourth century B.C., and in a way, these voyages were the prelude of oceanographic researches. In this connec- tion, the naval enterprices of the Phocaeans need to be mentioned in particular. Phocaea, the most northerly of the Ionian cities in Asia Minor pioneered the explo- ration and colonization of the western Mediterranean. From their settlement of Massilia (Marseilles), the Phocaeans undertook such expeditions as that to the North Sea, under Pytheas, and that to the African west coast, under Euthymenes. In the fourth century B.C., Aristotle also made important contributions to the knowledge of the sea, both as a naturalist and as a thinker. In his work Meteorologica, Aristotle mentions that currents flow from the Palus Maeotis (Sea of Azov) into the Pontus Euxinus (Black Sea) and from here into the Aegean, The cause of these movements was sought by him in the inequalities of depth in these seas. He thought that the Maeotis was being filled up and that it ultimately would become land. In the same work of Aristotle, we also find the first generalized, though inexact bathymetrical picture of the Internal Sea (Mediterranean). He records that the Pontus has parts, called whirlpools, wich are so deep that the lead never reached the bottom. With the exception of these deep places, the depth of the Inter- nal Sea was believed to increase towards the west. The Pontus was supposed to be deeper than the Maeotis, the Aegean deeper than the Pontus, and the Tyrrhenian and Sardinian Seas deeper than the Aegean. The Ptolemies, successors of Alexander the Great in Egypt, strongly promoted science in the third century B.C. Many learned men of the Alexandrian school published scientific work. Of these, the great influence of geodetical, astronomical and geographical studies of Eratosthenes (276-196 B.C.) should particularly be mentioned, because these prepared the way for the work of Hipparchus (?190-125 B.C.), whose name is especially associated with the introduction of projections in the tracing of charts and maps. Straton of Lampsacus, who was for some time the teacher of Ptolemy FI Phila- delphus in Alexandria, and from about 287-269 B.C. was the president of the school in Athens, believed that the Pontus Euxinus and the Mediterranean had earlier formed one closed sea with a much higher water level than they had in his time. The presence of marine shells and of salt deposits far in the interior of Libya was stated as evidence in favour of this conception. The Straits of the Bosporus, the Hellespont, and Gibraltar were believed to have been formed when the former sea burst its Marine Geol., 2 )4691( l 82 THE ORIGIN OF MARINE GEOLOGY 5 .) o a~ O .=. O i- e4 o~ barriers. In this respect, Straton recorded the occurrence of a submarine bank in the Strait of Gibraltar, uniting Europe and Africa. Modern science has definitely proved that such a bank exists, but at such a depth that it is hardly probable that it could have been found by ancient soundings. It would, therefore, be interesting to know how Straton obtained this knowledge. Marine Geol., 2 (1964) 1-28 6 A.A. NETNAM © e- 2 .=. 8 -d G Z4r~2 DZdTN-VT,I 5~ t<14 Romans Although the Romans extended their empire over most of the world they knew, they made few oceanographic discoveries. They were essentially a warlike and practical people. Scientific advances made in their times were often due to people of non- Roman descent, though generally possessing Roman citizenship. Marine Geol., 2 )4691( 1-28 THE ORIGIN, OF MARINE GEOLOGY 7 Polybius (?203-ca. 120 B.C.), the Greek historian of Rome wrote about marine sedimentation and pointed out that rivers debouching into the Palus Maeotis (Sea of Azov) carry into this sea considerable quantities of sediment; he estimated the time it would take the fluviatile alluvium to fill up both the'Palus Maeotis and the Pontus Euxinus (Black Sea) (Polybius, iv. 39-42). However, the rate of sedimentation is much slower than he supposed. Polybius reported that in his time, the greater part of the Sea of Azov was only 5-7 fathoms deep; about the same depths can still be found on modern hydrographic charts of that sea. From these Roman times, another mystery around ancient bathymetry needs to be reported. Posidonius (also often called R.hodius because of his stay on the island of Rhodus), a Stoic philosopher (135-51 B.C.), stated that he measured the depth of the sea in the vicinity of Sardinia down to 1,000 fathoms. Unfortunately, there is no mention of how he did his measuring; however, this is the first record of a deep-sea depth determination and fifteen centuries passed before the second known deep-sea sounding was noted down by Magelh~es. Posidonius also left the first record about the appearance of a new volcanic island, one in the Lipari group. The movements of the land caused by earthquakes and volcanic eruptions showed him that the surface of the earth might be modified under the influence of these forces. This led him to believe that the Atlantis of Plato might not be pure fiction. Also in Roman times, the Greek geographer Strabo (ca. 64 B.C.-at least 21 A.D.) wrote a comprehensive work about the physiography of land and sea. In the view of Strabo, all things on the crust of the earth are in a continual state of change. ./... . . . . . . . . . . . . . . .---" '".. / e:9 ~.S:Z ................. ',. '< l(~-"~c-'-" A s ~V ~ ,,"~' Fig.4. The world, according to Strabo 81( A.D.). Marine Geol., 2 )4691( 1-28 A. A. MANTEN The present relief of the surface of the earth is due to these modifications. The distri- bution of land and sea has therefore not always been the same. Earthquakes and volcanic eruptions make the land move. Movements of the ocean floor are produced even more easily as the crustal material there is as if it were made plastic by the water. With rises of the bed of the ocean, dry land is invaded by the waters; these oceanic waters retire when the ocean floor descends. Oceanic islands are considered to be of volcanic origin. The greater islands closer to land are supposed to have once formed part of the continents, but were detached by dislocations. Even the continents them- selves are regarded as being subject to oscillations and might have been raised from the bottoms of the various seas. He also believed that there is a relief on the sea floor with valleys and mountains similar to that on dry land. Strabo also paid attention to erosion and sedimentation. He states that running water can produce profound modifications on the surface of the land, depending upon the nature of the country through which the streams and rivers flow. Torrents coming down from mountains have a great erosive power, and the same holds for rivers flowing over soft or sandy ground. Both spread out over plains and great quantities of alluvial matter are tr~,nsported by them to the sea. He noted that material brought in suspension to the sea is not transported to great distances in this sea, but is soon arrested by the movements of the s~a. Therefore, sedimentation of sandy materials takes place mainly near the coast, where modifications of the surface of the earth are thus greatest, with the result that one can easily get an exaggerated impression of the rate at which the bed of the ocean is being filled up. Strabo strongly rejected the view of writers who argued that the sediment brought to the Pontus Euxinus by rivers could have any considelable effect in filling up that sea and causing it to overflow. Several statements concerning geological phenomena are found in the works of Ovid. In book XV of the ,sesohpromateM Pythagoras is presented giving an account of many facts and processes of nature, such as the elevation and depression of great land areas and the great changes which these movements bring about, erosion caused by flowing water, and other subjects. However, Ovid lived about 43 B.C. ?17 A.D., and Pythagoras five centuries earlier. The latter left no works and even in Aristotle's days, he was already obscured by legend. Several passages in Ovid's poem suggest that he was giving the then-current conception of Pythagoras' teachings rather than an actual survey of knowledge which the Greek philosopher could have possessed. Seneca had good notions about the erosive action of water. In his Naturales senoitseauQ (dated about 63 A.D.), he stated that all rocks, including even the hardest, are penetrated by watel. Due to a presence of a gas (spiritus) in this water, it is con- tinually active in dissolving and disintegrating the rocks and transporting their com- ponents, often to far from their place of origin. The water also has considerable mechanical effects on the rocks. Not even the hardest rock c~n resist the destructive action of a repeated dripping of water, and such action is much more pronounced when the forces in play are those of streams, currents, and the waves of the se~. Water attacks and destroys rocks everywhere, with chemical erosion often preceding the mechanical effects. Streams and rivers always pick up demolition material from Marine Geol., 2 (1 964) 1 28 THE ORIGIN OF MARINE GEOLOGY 9 ...:. Q O ,..,e,d~ 3h ,.6 g., O Dc .., Marine Geol., 2 (1964) 1-28 10 A.A. NETNAM their beds, especially during floods. Sea waves exert even more erosive action than run- ning water; this is well demonstrated by cliffs which are broken and smashed into ruins along several sea coasts. A large part of the material carried by rivers is trans- ported into the sea. Part of it is deposited at the mouth of the rivers, thus forming deltas. The smaller mineral particles are often brought to great distances from the shore before they are deposited on the sea floor. Tides and currents are mentioned among other factors which contribute to the pattern of marine sedimentation. Oceanographic observations in classical times more or less reached an end with the Hellenistic astronomel and geographer, Claude Ptolemy, who lived in Alexandria in the second century A.D. His famous map (Fig.5) shows the Oceanus indicus as an enclosed sea bounded by Africa, southern Asia, land extending from Sinae southward, and a Terra incognita in the south. The historical influence of Ptolemy is well demon- strated by the fact that this interpretation of the Indian Ocean was held until the second half of the eighteenth century. MIDDLE AGES After the fall of the Roman empire (fifth century), little was added to our knowledge ot the sea for the next twelve centuries. In the west, there was initially a great retrogression from the advanced ideas of the Greek geographers and naturalists. In the sixth century Ter~ u~ Oce~, u/~/~ ~ d//zo//u~ ha/~/.t~s,~t hom/n~s )¢ Fig.6. World map of Cosmas Indicopleustes (sixth century). Cosmas held the earth to be not a sphere, but a quadrilateral plane 400 journeys, or stations, of 30 miles each in length and half that distance in breadth. The earth is surrounded by the ocean and beyond this ocean is a second earth which everywhere reaches to the walls of heaven. Man was created at the eastern side of this transmarine earth, where Paradise was also located. When our ancestors were driven out of Paradise, they went westward (see top part of map), and with the deluge, Noah and his sons were carried in the ark to the land which we now inhabit. The four rivers of Paradise are conveyed by subterranean channels to our present land. Marine Geol., 2 (1964) 1-28