Ocean Highways

OUR PLANET 9.5 - Oceans

Ocean Highways


describes how 'rivers with banks of water' enabled early man to use the oceans to spread across the globe

Water offered man his first highways in rivers through the continents and currents across the seas. Before man ventured into the ocean, rivers took him through landscapes covered by thick forests that hid unknown enemies. Early settlements developed into ocean ports at river mouths and the migrations that penetrated Asia, Africa, Europe and America took full advantage of nature's inland waterways. Founders of civilizations were lured along the Indus, Euphrates, Tigris, Nile, Volga, Danube and Magdalena, to mention just a few.

We notice the rivers no matter how slowly and smoothly they may flow through the land. But we do not see the ocean currents and are therefore apt to forget the greatest and mightiest of all streams; those which have banks of water and flow invisibly through the sea. The largest river with its source in Peru is not the Amazon, flowing eastward through Brazil, but the Humboldt Current flowing westward through the Pacific. The mightiest river of Africa is not the Nile, but the Canary Current with its delta between the Caribbean Islands, emptying African sea water into the Mexican Gulf. The fixed itineraries of these marine rivers span the oceans and form paths between the continents.

The invisible rivers which float across all major oceans, stronger and larger than any river ashore, are held in constant motion by nothing less than the rotation of the Earth itself. They flow from east to west in the tropical belt: striking continents they turn, each in a wide loop, coming back east in colder latitudes as near as possible to the Arctic and Antarctic regions. These tropical currents do not move alone; they pull with them any floating thing, while above the sea the eternal forceful trade winds blow at full strength in the same general direction, from east to west, the year around. Dwarfing the continental rivers as conveyor belts, they are even more one-way directed by the permanent company of these winds. Where visible coasts and premeditated decisions have not guided man in search of new land, the invisible marine conveyors have been ever present to lure him from one coast to the next, with or without the traveller's own wish and awareness. History shows that these conveyors played a principal part in European discoveries of other continents and islands inaccessible to them before the development of buoyant water craft.

History and oceanography concur in pointing out three favourable ocean highways from the Old World to the New, two on the Atlantic side and one on the Pacific; and three main routes of departure, one on the Atlantic side and two on the Pacific. The routes are so clearly defined that each may well be named after its historically recorded discoverer:

I - The Leif Erikson route (North Atlantic): the one least favoured by the elements, but first used by Europeans because it offers stepping stones to America from Norway or Great Britain by way of the Shetlands, the Faeroes, Iceland, Greenland and Baffin Island. Between AD 986 and about AD 1500 the Norsemen founded and maintained settlements with 280 farms, two episcopal residences, monasteries and churches on the southwest coast of Greenland. These early European colonists lived only some 320 kilometres from the American coast for five centuries before the arrival of Columbus, maintaining their cumbersome contact with Iceland and Norway by open boat, and regularly supervised and taxed by the Vatican. Written records from the 11th to the 14th centuries document at least five visits from Greenland to the New World just on the other side of the Davis Strait.

II - The Columbus route (Atlantic): This is considerably longer, but offers very gentle climatic conditions and extremely favourable currents and winds. Although fed by waters from Western Europe, it actually originates off Gibraltar and the northwest African coast, where it joins company with the trade winds. From North Africa it follows the North Equatorial Current straight to the Caribbean Islands and into the Gulf of Mexico. The current receives a strong southern feeder from Madagascar and South Africa, the South Equatorial Current, which enters the Gulf of Mexico, but by way of the Brazilian coast. These two can be seen as subdivisions of a vast conveyor, which hits the American continent and is pushed northwards to turn and flow back towards Europe as the Gulf Stream. Columbus and his early European followers all returned along this route. It must also have been followed by the primitive vessel carrying dead bodies, washed up in the Azores, which Columbus took as a sign that there was land to the west.

III - The Mendaña or Inca Route (South Pacific): The westward progress of wind and water along the Columbus route - interrupted by its collision with Central America - is immediately resumed on the Pacific shore, where the North and South Equatorial Currents push on westwards with the same trade winds. Inca sailing directions stimulated and guided Mendaña's party of explorers along this route, whose short and powerful sweep linked the world's most isolated inhabited island groups to a new world coast abounding in buoyant watercraft. Its strength lies in the extremely powerful South Equatorial Current, also known as the Peru or Humboldt Current, followed by very strong trade winds and fed by water sweeping northward along the South American coast from Chile and turning sharply west off the north coast of Peru. Its northern edge touches the Galapagos Islands, its southern edge touches Easter Island, and its main flow embraces all the inhabitable land in Polynesia (except Hawaii) and Melanesia, before spreading out into a sort of delta where New Guinea and Australia interfere with its free passage.

Its flow is periodically disturbed by a small and usually insignificant current which runs down the coast of Ecuador from the Panama Gulf and, in normal years, turns west at the latitude of the Galapagos Islands: the early Spanish explorers called this the Niño or Baby Current because it generally appeared around Christmas. At irregular intervals, often of eight or ten years, it suddenly enormously increases in strength and sweeps down the coast of Northern Peru, changing the weather worldwide. In such years of disaster and famine the Peru Current is forced westwards at more southerly latitudes, bearing straight down upon Easter Island.

IV - The Saavedra route (Pacific): This runs parallel to the Mendaña route from Mexico to Indonesia on the north side of the equator, spanning the entire width of the tropical Pacific. Its speed, and the force of the trade winds, rival the South Equatorial. It offers less obvious opportunity for discovery than does the Mendaña route in the island-studded latitude of Peru: Saavedra crossed the ocean in the empty belt south of Hawaii and north of Polynesia proper.

V - The Urdaneta Route (North Pacific): This begins where the Saavedra route ends, in the Philippine sea. Here the warm water of the North Equatorial Current, blocked by Indonesia, turns north. It passes Japan and moves south of North America in a long sweep from Alaska to lower California. It combined with the Saavedra route to form the once important caravel route followed by all Europeans crossing the Pacific in the early days of sail.

The Mendaña, the Saavedra and the Urdaneta routes are the only natural conveyors across the Pacific. The so-called Equatorial Counter Current, which figures prominently on many maps as running in an eastward direction between the two wide westbound currents, is no more than a narrow belt of eddies and upwellings in latitudes of calms and confusing winds - the doldrums, dreaded in the days of sail. For 500 years, between Marco Polo's travels in the 1270s and Captain Cook's voyages in the 1770s, no European navigator, however intrepid, could force his ships from Asia into Oceania by way of Papua-Melanesia or Micronesia. This gives us a realistic picture of even greater restrictions imposed on primitive explorers.

Four basic misconceptions inhibit discussions on the possibilities of primitive seafaring.

1 - A watertight hull is not the only - or the best - solution for security at sea. In a vessel with a wash-through body the building material is self-buoyant, boring worms are no threat, and bailing is superfluous since any sea breaking on board will merely run through and leave the vessel on top of the waves. Its shallow draft and compact body structure permit it to voyage among reefs and shoals and make crash landings on coasts which no hulled vessel could approach.

2 - It is wrong to believe that security in ocean travel invariably increases with the size of the vessel and the height of its deck above sea level. It is a great advantage to be small enough to move freely between and over the swells: a boat much over 10 metres long will either be forced to bury its bow or stern into surrounding waves, or will bridge two waves simultaneously, risking breaking amidships.

3 -The idea that it is easier and safer for primitive navigators to hug the continental coastline than to cross an open ocean is a very common - and mistaken - illusion. Whether in storm or normal conditions, the steepest and most dangerous waves occur where ocean rollers meet the backwash from cliffs, increasing in chaotic interference with tides and deflected currents. In mid-ocean there are no rocks or reefs to interfere with the progress of either craft or currents; the swells are drawn long and regular, and the peril of wrecking is reduced to an absolute minimum.

4 - The logical conclusion that the distance from A to B equals the distance from B to A is correct ashore, but wrong at sea. The distance from Peru to the Tuamotu islands is 6,500 kilometres, for example, but the Kon-Tiki covered only about a quarter of that distance in making this journey. This, of course, is because the ocean surface displaced itself by about 4,800 kilometres in the direction of Polynesia during the 101-day period of the crossing. The raft benefited from an invisible free lift from the Humboldt Current, running like a river. If another aboriginal type of vessel had been able to sail with a straight course in the opposite direction at the same speed, it would have had to move upstream and cross no less than 11,000 kilometres of running sea water to reach Peru from the Tuamotu archipelago - about seven times the sailing distance and time confronting the Kon-Tiki, though the distance would be exactly the same on a map. And as no sailing vessel can advance directly into the wind, it would also have had to tack against the powerful trade winds, adding another couple of thousand kilometres to the itinerary.

Ashore early migrants had to struggle to make discoveries whilst at the same time providing for themselves. At sea, however, great discoveries could be made just by sitting quietly on a vessel and fishing.

Dr. Thor Heyerdahl, the explorer and author, is based in Tenerife.

Complementary articles in other issues:
Frank A. Campbell: Whispers and waste (Small Islands) 1999

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