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The Galápagos archipelago (officially named the Archipiélago de Colón ) is in a constant state of change due to tectonic activity: volcanic eruptions form and reshape islands, while sea-floor spreading pushes them toward the continent. The Galápagos officially encompass a total land mass of 7880 sq. km (4900 sq. miles) divided among thirteen large islands, six smaller islands, and over forty officially named islets. The major islands all have an area greater than 10 sq. km, the largest of which is the western island of Isabela at 4588 sq. km (2850 sq. miles), more than half of the total land area in the Galápagos. Isabela also contains the archipelago's highest point, Volcán Wolf, with an altitude of 1701 meters (5600 feet).
Besides their unique geological history, the Galápagos receive much of their scientific—as well as tourist—fame for their extreme geographic isolation. The islands straddle the equatorial line at the 90 th meridian west, a point in the Southeast Pacific Ocean . The nearest continental land mass is mainland Ecuador, which is almost 1000 kilometers (620 miles) to the east. Costa Rica 's Cocos Island is archipelago's nearest neighbor, lying about 720 kilometers (450 miles) to the northeast.
The Galápagos Islands are generally categorized and clumped according to their relative positions in the archipelago at cardinal points on the map. The northern islands—Genovesa, Marchena, and Pinta—are those that are outlying to the north, above the equatorial line. The central islands are all islands within a limited radius (a few hours in transit) of the main thoroughfare islands of Baltra and Santa Cruz , which include Daphne, North Seymour, Santa Fé, North and South Plazas , Bartolomé, Santiago , Sombrero Chino, and Rábida. The southern islands encompass the three large islands in the lower archipelago—Floreana, Española, and San Cristóbal . And the western islands are the young islands closest to the geological hot spot—Isabela and Fernandina.
The location of the archipelago also coincides with the meeting point of three major oceanic currents: the cold Humboldt Current arriving from the southeast, the warm Panama current from the northeast, and the cold Cromwell countercurrent from the central Pacific. The convergence of these currents has a profound influence on marine temperature schema, manifesting in five distinct sea surface temperature zones: one around the central island of Santa Cruz, one in the warmer northern islands, one in the cooler southern islands, one in the cold western sector of the Galápagos, and a fifth transition zone where mean temperatures have the most dramatic seasonal fluctuations.
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