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Clipperton / Ile de la Passion - Geography

Clipperton Island is located in the Pacific Ocean by 10 ° 18 'North and 109 ° 13' West. It is more than 6,000 km from Tahiti and 1,300 km from the coast of Mexico. Definitive property of France since 1931, the Clipperton atoll is a lost pinhead in the eastern Pacific off the main shipping routes. Its geographical location close to Ecuador, its exclusive economic zone (EEZ), its isolation, its unique ecosystem and its supposed wealth, stir up many passions to the point of urging France to study the future of this overseas territory.

This isolated atoll was named for John CLIPPERTON, an English pirate who was rumored to have made it his hideout early in the 18th century. Surrounded by an Exclusive Economic Zone of 425,000 km², the island is an isolated atoll of subcircular form of 6 km² of which about 2 km² of land emerged. It has a lagoon closed and isolated from the masses of ocean waters, surrounded by a narrow strip of land.

During severe storms, the island receives in the northeast and southeast areas the oceanic water that then flows into the lagoon. The atoll is surrounded by a coral platform exposed at low tide. The island encompasses at its southeast end a rock of volcanic origin (29 meters).

Clipperton Island bears the distinction of being the only coral island of the eastern Pacific. It is a true atoll, two miles across in its longest diameter. It lies in latitude 10°17' north and longitude 109°13' west, being almost directly south of Cape San Lucas, Lower California, and west of the northern part of Costa Rica. It is about 600 miles distant from the nearest place on the mainland, which is Tejupan Point at the south end of Manzanilla Bay, between San Bias and Acapulco, Mexico.

Its climate is hot and very humid. The water about it is warm and the currents westerly. The Mexican current, which flows southeast along the coast of Mexico, is deflected to the westward in the latitude of Clipperton. Hence, the currents which bathe the island come directly from the mainland, and are responsible for the animals and plants now carried there by natural agencies. The land fauna is very scant. Besides birds a lizard, Lagosoma erundeli, occurs there; also an Agrionid dragonfly, a Cicindelid beetle and a very few Diptera. The nymphs of the dragonflies live in the brackish lagoon inside the circular coral bank. No land plant is native to the island, and the birds and crabs are everywhere so abundant that no plant could possibly grow there unless artificially protected.

The island is roughly circular, being composed of a narrow ring formed of sand and pieces of coral. Its width varies from 200 to 1,300 feet, averaging in most places between 300 and 600 feet. The interior of the island is occupied by a lagoon of brackish water full of algae. According to P. J. Henning's chart of Clipperton Island, made in 1897, its depth, near the center is forty fathoms, and at one point south of the center, fifty-five fathoms. Everywhere near the shore it is shallow, but the bottom slopes off very irregularly toward the center. The depth varies slightly, probably according to the rainfall, for the lagoon was, in 1898, entirely shut off from the ocean.

According to Henning's chart the water over a reef in the middle of the lagoon was only from two to eight inches deep. During a visit in November, 1898, the reefs were everywhere two feet, and in most places much more, beneath the surface of the water. This reef crosses the middle of the lagoon in a northwest-southeast direction along the line of the greatest diameter of the atoll. Near the northwest shore of the lagoon are several small islands on which one of the terns of the island, Sterna fuliginosa, was nesting in great numbers during our visit.

The height of the island is uniformly very low and its surface flat, except on the outer side where it slopes off rather steeply to the ocean, and on the inner side where it slopes more gently to the lagoon. Everywhere, except at one place, it is composed of irregular fragments of coral stems. Where sections of the banks have been cut by water, the material below the surface is seen to be exactly the same as that at the surface, except that it is compacted into solid beds. No coral sandstone rocks were found. The pieces of coral scattered about just above high-water mark have smoothed and polished surfaces, though still preserving their branched shapes. Lower down the coral fragments are worn by the waves to rounded pebbles, and finally ground up into sand.

All around the island a sloping reef runs outward from high-water mark. Its variable width is generally equal to or slightly greater than the part of the island above water. Soundings at the anchorage on the north side of the island at a distance of seven hundred feet from the outer edge of the reef show depths of 38, 46 and 60 fathoms, while at the edge of the reef, just outside of lowwater mark, the depth is only about 20 fathoms.

Near the middle of the east side of the island is a large mass of dark igneous rock, about sixty feet high, which is not found elsewhere on the island. It is much eroded by water; its exterior is cut into numerous pinnacles and irregular projections, and its interior is hollowed out by caves. Large passageways extend entirely through the mass. The rock is so worn by the water that it has the appearance of being a large isolated block of sandstone. It is, however, simply the surviving remnant, above water, of the original volcanic island on which the coral atoll has been built. In places the surface of the rock is decomposed into a soft, whitish material, easily broken between the fingers. The excrement of birds upon it in other places has made on the surface a white, glassy formation.

The rock is in lat. 10° 17' N., long. 109° 10' W.; it is sufficiently lofty to be seen from a distance of 12 or 15 miles. When first in sight it appears not unlike a sail, but on a nearer approach it presents the appearance of an immense castle. The colour is very dark, in fact nearly black. This most dangerous island (and rock) is but little known, and thought by many not to exist. Its vicinity is generally indicated by the presence of numerous sea-birds — the white gannet, wide-awake, and booby, which are often found as much as 50 or 60 miles from the rock.

Sir Edward Belcher, who visited it in May, 1839, and after mentioning that for a distance of about 15 miles, the rock presented the appearance of a brig close hauled, owing to the sun's rays playing on its nearest face, he proceeds to say: “the name, Clipperton rock, certainly misled us, and had we made the point at night, with a fair wind, would, almost inevitably, have severely damaged or destroyed both vessels. I certainly should have steered to pass it to the northward; merely assuming it to be a solitary rock. • “Nothing in this name would lead a seaman to imagine a high rock, placed on the southern edge of a coral lagoon island, 3 miles long north and south, by the same east and west.

“Its description should stand thus:—A very dangerous low lagoon island, destitute of trees, with a high rock on its southern edge, which may be mistaken for a sail. “This rock can be seen 15 miles. In thick weather the low coral belt, which appears like sand, will not be distinguished until close to it. The breakers on the eastern side of it do not afford sufficient warning for a vessel to trim or change course. On the northern part of the belt, the land is a little raised, and appears to be clad with something like grass."

Abyssal ocean depths lie between Clipperton Island, the mainland, and the other four island groups of the tropical eastern Pacific Ocean (the Revillagigedo Islands of Mexico, Cocos Island of Costa Rica, Malpelo Island of Colombia, and the Galápagos Islands of Ecuador). The Clipperton fracture zone, trending roughly east-west for 3,300 miles between 127° W long and 96° W long, is divisible into four zones from west to east: a broad, low welt 900 miles long with central trough 10–30 miles wide; a volcano-studded ridge, here called Clipperton Ridge, 60 miles wide and 330 miles long with local relief of 18,000 feet; a low welt with central trough transecting the Albatross Plateau which is the northernmost part of the great East Pacific rise; and a zone of bifurcation east of Albatross Plateau the major branch of which, Tehuantepec Ridge, trends to the northeast and thus deviates from the great circle trend followed by the four great fracture zones so far discovered in the northeastern Pacific.

Three of the known great ridges, similar to Clipperton Ridge in size, relief, and position within east-trending fracture zones of the northeastern Pacific, occur at an intersection with northwesterly trending zones; thus it is possible that some northwesterly-trending lineation intersects the Clipperton fracture zone near Clipperton Island.

Throughout the Pacific basin transcurrent faults and submarine fracture zones are associated With and limit most oceanic trenches and island arcs. No causative relation is suggested between the two, however, because many of the transcurrent or linear features such as the Clipperton are too long to be of local origin and lie at all angles to the trenches and island arcs. It is probable that the lineations are a part of a pattern of faults which broke the crust of the Pacific Basin and China into large blocks in early geological history. Forces which formed the island arcs and trenches may possibly act on an area larger than one of these older blocks but the structures which they produce are discontinuous at the edges of the blocks.





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Page last modified: 24-07-2017 18:30:51 ZULU