Mona Passage
The Mona Passage is a strait
A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...

 that separates the islands of Hispaniola
Hispaniola is a major island in the Caribbean, containing the two sovereign states of the Dominican Republic and Haiti. The island is located between the islands of Cuba to the west and Puerto Rico to the east, within the hurricane belt...

 and Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

. The Mona Passage connects the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 to the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....

, and is an important shipping route between the Atlantic and the Panama Canal
Panama Canal
The Panama Canal is a ship canal in Panama that joins the Atlantic Ocean and the Pacific Ocean and is a key conduit for international maritime trade. Built from 1904 to 1914, the canal has seen annual traffic rise from about 1,000 ships early on to 14,702 vessels measuring a total of 309.6...


The 80 mi (128.7 km) stretch of sea between the two islands is one of the most difficult passages in the Caribbean. It is fraught with variable tidal currents created by the large islands on either side of it, and by sand banks that extend out for many miles from both coasts.


There are three islands in the Mona Passage:

Mona Island
Mona, Puerto Rico
Mona is the third largest island of the archipelago of Puerto Rico, after the main island of Puerto Rico and Vieques. It is the largest of three islands located in the Mona Passage, a strait between the Dominican Republic and Puerto Rico, the others being Monito Island and Desecheo Island...

 lies close to the middle of the Mona Passage.

Five kilometers northwest of Mona Island is much smaller Monito Island
Monito Island
Monito Island is an uninhabited island about 5 kilometers northwest of much larger Mona Island. Monito is the masculine diminutive form of Mona in Spanish. It is one of three islands in the Mona Passage, and part of the Isla de Mona e Islote Monito barrio, a subdivision of the municipality of...


Fifty kilometers northeast of Mona Island and much closer (21 km) to the Puerto Rican mainland is Desecheo Island
Desecheo Island
Desecheo is a small uninhabited island of the archipelago of Puerto Rico located in the northeast of the Mona Passage; 21 km from the west coast of the main island of Puerto Rico and 50 km northeast of Mona Island. It has a land area of 1.5 km² . Politically, the island is...


Structure and seismicity

The Passage was also the site of a devastating earthquake and resulting tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 that hit western Puerto Rico in 1918. It is the site of frequent small earthquakes. The passage is underlain by a seismically active rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 zone that overprints an older partly eroded tilted-block structure. Desecheo Island sits on the Desecheo ridge, a narrow east - west ridge that extends west from the northwest corner of Puerto Rico. The ridge forms the southern boundary of the 4000 m deep Mona rift which extends toward the north to the strike slip fault zones which bound Puerto Rico and Hispanola. The east face of the rift has a sharp relief of 3 km and is controlled by the N - S trending Mona Rift Fault. The epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...

 of the 1918 earthquake was located along the east or southeast edge of the Mona Rift.


Most cruising boaters entering the Caribbean from the north do so via a stop at Samaná in the northeastern part of the Dominican Republic
Dominican Republic
The Dominican Republic is a nation on the island of La Hispaniola, part of the Greater Antilles archipelago in the Caribbean region. The western third of the island is occupied by the nation of Haiti, making Hispaniola one of two Caribbean islands that are shared by two countries...

, then continuing across the Mona Passage to Puerto Rico without stopping. Under sail it means an even longer distance because of having to "tack" a zig-zag course into the easterly trade winds.

At the stop of Saona Island
Saona Island
Saona Island is a tropical island located a short distance from the mainland on the south-east tip of the Dominican Republic, near La Altagracia Province. It is a government protected nature reserve and is part of East National Park...

 on the southeast coast of the Dominican Republic, boaters can sit and wait for a lull in the trade winds when seas are down to start their eastward crossing. This is an advantage which is not possible when departing from Samaná. It is only about 40 miles (64.4 km) from Saona to the protected anchorage inside the barrier coral reef on the west coast of Mona Island. And from there it is another 40 miles (64.4 km) to the popular and spacious cruising anchorage at Boquerón
Boquerón, Puerto Rico
Boquerón is a beach village located in the town of Cabo Rojo, Puerto Rico. The village is one of the main tourist attractions in the southwestern part of the island. As of the United States 2000 Census, the barrio population was 4,963....

in Puerto Rico.
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