The Tectonic Setup and also Geology of Puerto Rico as well as Its Surrounding Seafloor
By Michael Cheadle - College of Wyoming
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The island of Puerto Rico hinges on a vibrant plate-boundary area in between 2 structural plates: the North American plate as well as the northeast edge of the Caribbean plate (Number 1). The area is extremely seismically energetic with approximately 5 quakes (consisting of aftershocks) with a size more than 1.5 taking place near Puerto Rico daily throughout the last year (March 2014-March 2015). Although the large bulk of these quakes are as well tiny to be really felt by individuals, these quakes offer proof that the North American plate is relocating westward about the Caribbean plate at regarding 2 centimeters/year.
The north limit of the Caribbean plate is sub-parallel to the loved one instructions of activity of both plates, to make sure that home plates primarily move previous each various other. Nonetheless, the activity is somewhat oblique to home plate limit (see the arrowhead in Number 1) and also the North American plate is partly assembling with the Caribbean plate and also being obliquely subducted underneath Puerto Rico (Number 2).
On the other hand, the eastern limit of the Caribbean is around vertical to the family member activity of the North American plate (Number 1) therefore below, the North American plate is being lowered below the Caribbean plate as well as subducted right into the mantle, producing the energetic volcanic island arc of the Lesser Antilles.
Structural Background of Puerto Rico
Puerto Rico itself is a now-extinct volcanic island-arc terrane which began to expand around 190 million years back. The island started life as an energetic volcano, created by melting of the mantle as the Pacific plate subducted listed below the west shore of South America at regarding the contemporary latitude of the Peru-Ecuador boundary. Starting about 80 million years earlier, the island-arc was rafted northward and after that eastward as the North as well as South American layers pressed westward around the freshly developing Caribbean plate.
These older volcanic rocks are overlaped by more youthful (much less than 30 million years of ages) carbonates and also various other stratified rocks. The carbonate rocks expand off the north coast pf Puerto Rico as a carefully dipping system that develops the southerly end of the Puerto Rico Trench (Number 1).
The Trenches as well as Canyons Surrounding Puerto Rico
The north border of Puerto Rico is noted by the 800-kilometer-long Puerto Rico Trench, which is the undersurface of the Atlantic Sea, with an optimum deepness of 8,648 meters (Number 1). It is the 8th inmost trench worldwide and also the inmost seafloor outside the Pacific Sea. The trench was developed by the oblique merging as the North American Plate lowered underneath the Caribbean Plate.
Number 3 reveals a north-south area throughout the Puerto Rico Trench attracted at the exact same range as 3 various other deep canyons to highlight its substantial dimension: the Mona Canyon, which exists simply to the south of the Puerto Rico Trench (Numbers 1 as well as 4); the Kali Gandaki Canyon in Nepal, among the inmost chasms located on the continents; as well as the popular Grand Canyon in Arizona.
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Puerto Rico is bounded on the south by the Muertos Trough, on the west by the Mona Canyon, as well as on the eastern by the Virgin Islands Container (Number 1). The Muertos Trough is a lengthened container created where the Planet’& rsquo; s crust to the south of Puerto Rico is propelled under the Muertos fold-and-thrust belt, which exists to the south of the island. Mona Canyon (Number 4) is an around north-south trending canyon which is virtually 30 kilometers throughout, developed by east-west rifting.
The center of the 1918 San Fermin size 7.5 quake lies simply to the north of the Canyon and also the quake was most likely brought on by faulting pertaining to this rifting. This quake caused a six-meter high tsunami wave that brushed up along the west shore of Puerto Rico as well as might have created the huge landslide displayed in Number 4.
Last but not least, the Virgin Islands Container is an extensional container which exists at the south-western end of the Anegada Trough, a function that was checked out in 2013 and also 2014 by the E/V Nautilus With Each Other the Muertos Trough, the Mona Canyon, the Virgin Islands Basin/Anegada Trough, as well as the Puerto Rico Trench, specify the margins of the Puerto Rico-Virgin Islands microplate, a tiny systematic block caught in between the bigger Caribbean as well as North American layers.
Throughout the program of Leg 3 of Océano Profundo 2015: Checking out Puerto Rico's Seamounts, Trenches, as well as Troughs, every one of these significant trenches and also canyons will certainly be checked out by Okeanos Traveler making use of the from another location run lorry, Deep Innovator