Roca Partida ( en, Split Rock) ranks as the smallest of the four

Revillagigedo Islands The Revillagigedo Islands ( es, Islas Revillagigedo, ) or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem. They lie approximately from Socorro Island south and southwest of C ...

, part of the Free and Sovereign State of

Colima Colima (), officially the Free and Sovereign State of Colima ( es, Estado Libre y Soberano de Colima), is one of the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima i ...

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

. The uninhabited island (Latitude 19° 0'2.53"N, Longitude 112° 4'5.35"W) encompasses an extremely small area. Many divers rank it among the most beautiful dive sites in Mexico. Divers must obtain permits from the

Mexican Armed Forces The Mexican Armed Forces ( es, Fuerzas Armadas de México) are the military forces of the United Mexican States. The Spanish crown established a standing military in colonial Mexico in the eighteenth century. After Mexican independence in 1821, ...

to enter the military zone surrounding the island.

Geography

The four

originated as

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

es.

San Benedicto Island San Benedicto, formerly Isla de los Innocentes, is an uninhabited island, and third largest island of the Revillagigedo Islands, located in the Pacific Ocean. It is 4.8 km by 2.4 km in size, with an area 10 km². It is of volcanic ...

and

Socorro Island Socorro Island ( es, Isla Socorro) is a small volcanic island in the Revillagigedo Islands, a Mexican possession lying off the country's western coast. The size is 16.5 by 11.5 km (10.25 by 7.15 miles), with an area of . It is the larges ...

erupted in 1953 and 1993, respectively. Clarion Island and Roca Partida lack recently known eruptions.

Erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...

over millennia reduced Roca Partida to a piece of bare rock, devoid of terrestrial vegetation. Roca Partida, long and wide, rises into two peaks. A low-lying bare rock area divides the two peaks, hence the name "Split Rock." The two peaks measured and high in 1953, but the higher peak apparently lost several meters (feet) since then, as the photographs illustrate.

Fauna

Roca Partida lacks

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...

and supports no land animals. Nevertheless, the waters surrounding the islet teem with marine life. Several species of

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...

breed on the rock, including the

Nazca booby The Nazca booby (''Sula granti'') is a large seabird of the booby family, Sulidae, native to the eastern Pacific. First described by Walter Rothschild in 1902, it was long considered a subspecies of the masked booby until recognised as distinct g ...

(), which probably ventures little farther to the northeast; the Northeast Pacific

brown booby The brown booby (''Sula leucogaster'') is a large seabird of the booby family Sulidae, of which it is perhaps the most common and widespread species. It has a pantropical range, which overlaps with that of other booby species. The gregarious b ...

(); the East Pacific

sooty tern The sooty tern (''Onychoprion fuscatus'') is a seabird in the family Laridae. It is a bird of the tropical oceans, returning to land only to breed on islands throughout the equatorial zone. Taxonomy The sooty tern was described by Carl Linna ...

(), a doubtfully distinct subspecies; and the East Pacific

brown noddy The brown noddy or common noddy (''Anous stolidus'') is a seabird in the family Laridae. The largest of the noddies, it can be told from the closely related black noddy by its larger size and plumage, which is dark brown rather than black. The ...

().

History

The island's first reported sighting was in November 1542 by the Spanish expedition of

Ruy López de Villalobos Ruy López de Villalobos (; ca. 1500 – April 4, 1546) was a Spanish explorer who sailed the Pacific from Mexico to establish a permanent foothold for Spain in the East Indies, which was near the Line of Demarcation between Spain and Portugal ...

, who charted it with its present-day name.

References

External links

Marine Life of Roca Partida

Scuba Diving in Roca Partida

Revillagigedo Islands Islands of Colima Pacific islands of Mexico Stacks (geology) Volcanoes of Colima Uninhabited islands of Mexico {{Colima-geo-stub