The Chortis Block is a 400–600 km (250–370 mi)-wide continental fragment in Central America ( Honduras , Nicaragua , El Salvador , Guatemala , and the off-shore Nicaragua Rise ) located in the northwest corner of the oceanic Caribbean Plate .
8-721: The northern margin of the Chortis Block is the Motagua - Polochic fault of the North American - Caribbean strike-slip boundary. The Cocos / Farallon Plate subducts beneath its western margin resulting in the Middle America Trench and the Central America Volcanic Arc . Miocene-Holocene-aged rifts in the northern and western Chortis Block is the result of slow internal deformation. The southern and eastern extent
16-591: Is a major, active left lateral-moving transform fault which cuts across Guatemala . It forms part of the tectonic boundary between the North American plate and the Caribbean plate . It is considered the onshore continuation of the Swan Islands Transform Fault and Cayman trench , which run under the Caribbean Sea . Its western end appears not to continue further than its surface trace, where it
24-462: Is covered by Cenozoic volcanics. The measured length of the fault is approximately 350 km and is the longest fault in Guatemala. Motion of the fault and others in the plate boundary have formed north–south trending grabens across the region that show evidence of counter-clockwise rotation over time. Guatemala City lies in one of these grabens, which may contribute to the seismic hazard posed to
32-643: Is roughly the Nicaragua- Costa Rica border and the offshore Hess Escarpment. The Chortis Block can be subdivided into several terranes , the names and extents of which varies considerably between different authors. During the Late Neoproterozoic-Early Palaeozoic the Chortis Block was probably located on the northern shores of what is now Colombia , then the northern margin of the Amazonian Craton , with an ocean separating it and
40-592: The city's inhabitants. The Motagua Fault is regarded by some geologists as part of a system of faults designated the "Motagua-Polochic system" rather than as a discrete single boundary. The Polochic fault (also referred to as the Chixoy-Polochic Fault) lies north and parallel to the Motagua Fault and shares some of the motion between the North American and Caribbean plates. Studies of GPS displacement of
48-643: The collision. Located in a largely unpopulated, mountainous region, the geology of which is poorly known, the Chortis Block is the only Precambrian-Palaeozoic continental crust on the Caribbean Plate and even its origin within North America has remained enigmatic and disputed for decades. Three models have been proposed for the origin of the Chortis Block: Motagua Fault The Motagua Fault (also, Motagua Fault Zone )
56-545: The other blocks from core North America or Laurentia . Before the Early Carboniferous formation of Pangaea the Chortis Block thus formed part of the northern margin of Gondwana , located south of other Peri-Gondwanan terranes such as Oaxaca , Carolina , Yucatán , and Florida . These blocks either escaped the Laurussia-Gondwana collision and were broken off Gondwana later, or were accreted to Laurentia during
64-435: The zone reveal that the motion of the North American / Caribbean plate Boundary is, for the most part, accommodated by the Motagua Fault. The Motagua Fault has been responsible for several major earthquakes in Guatemala 's history, including the 7.5 M w Guatemala 1976 earthquake , and is also notable for its significant visible fault trace . The event caused 2 meters of vertical displacement and ruptured 230 km of
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