Rocas Alijos, or Escollos Alijos ( en, Alijos Rocks) are a group of tiny, steep and barren

volcanic 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 plat ...

islets or above-water (as well as below-water) rocks in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

at . They are part of

Comondú municipality Comondú is a municipality of the Mexican state of Baja California Sur. It had a population of 70,816 inhabitants in 2010 census (INEGI). With a land area of 16,858.3 km2 (6,509.03 sq mi), it is the seventh-largest municipality in area in ...

of the

Mexican state The states of Mexico are first-level administrative territorial entities of the country of Mexico, which is officially named United Mexican States. There are 32 federal entities in Mexico (31 states and the capital, Mexico City, as a separate en ...

Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...

, and situated about west of the mainland. The total surface area is . The group consists of three principal rocks and numerous smaller ones. South Rock, the largest of the group, is high, with a diameter of only (position ). Middle Rock is high and about in diameter. North Rock, north of South Rock, is high, with a diameter of . The rocks in between those are either submerged or so low that they are barely visible among the heavily breaking waves. The rocks have been known since the early Spanish history of Mexico; they can be found on a map from 1598. Others have described their official discovery as coming in 1605. The first description is from 1704, by

pirate Piracy is an act of robbery or criminal violence by ship or boat-borne attackers upon another ship or a coastal area, typically with the goal of stealing cargo and other valuable goods. Those who conduct acts of piracy are called pirates, v ...

John Clipperton John Clipperton (1676 – June 1722) was an English privateer who fought against the Spanish in the 18th century. He was involved in two buccaneering expeditions to the South Pacific—the first led by William Dampier in 1703, and the second under ...

. The first exact description was made by a Spanish sailor in 1791. South Rock was climbed for the first time in 1990 by an expedition (October 31 through November 7, 1990) under the leadership of Robert Schmieder, who edited a

monograph A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monogra ...

about the rocks.
The group is located at the transition zone between two major biologic provinces, at a latitude where the Pacific Current turns westward to form the North Pacific trans-oceanic current. The rocks are nesting sites of many seabirds. The two other Mexican island groups in the Pacific Ocean that are not on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

are Guadalupe Island and

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 ...

Fauna

The breeding marine avifauna of Alijos Rocks currently consists of

Leach's storm-petrel Leach's storm petrel or Leach's petrel (''Hydrobates leucorhous'') is a small seabird of the tubenose order. It is named after the British zoologist William Elford Leach. The scientific name is derived from Ancient Greek. ''Hydrobates'' is fro ...

(a presumed breeder, probably a few pairs),

red-billed tropicbird The red-billed tropicbird (''Phaethon aethereus'') is a tropicbird, one of three closely related species of seabird of tropical oceans. Superficially resembling a tern in appearance, it has mostly white plumage with some black markings on the wi ...

(14 birds), masked booby (100), and

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 Linnae ...

(250). The

magnificent frigatebird The magnificent frigatebird (''Fregata magnificens'') is a seabird of the frigatebird family Fregatidae. With a length of and wingspan of it is the largest species of frigatebird. It occurs over tropical and subtropical waters off America, bet ...

is a regular winter visitor but probably does not breed. The Laysan albatross is currently an annual visitor to Alijos Rocks during its winter breeding season, and may start to nest there in the near future.

References

External links

Radio enthusiast's descriptionsailing directionsRocas Alijos: Scientific Results from the Cordell ExpeditionsThe Marine Birds of Alijos Rocks, MexicoCordell Expeditions HomepageRocas Alijos part of Comondú municipalityVideo: Tuna fishing beginning at Alijos Rocks, October 2005

Literature

*Robert W. Schmieder, Ed.: Rocas Alijos: Scientific Results from the Cordell Expeditions, Dordrecht; Boston: Kluwer Academic Publishers, 1996, (Series:

Monographiae biologicae ''Monographiae Biologicae'' () is a scholarly scientific literature review series, consisting of monographs published by Kluwer Academic Publishers, an imprint of Springer Science+Business Media. The series subject area generally covers ecology, z ...

, v. 75) {{Authority control Islands of Baja California Sur Pacific islands of Mexico Stacks (geology) Extinct volcanoes Volcanoes of Baja California Sur Volcanoes of the Pacific Ocean Comondú Municipality Natural history of Baja California Sur Seabird colonies Uninhabited islands of Mexico