Forming the Atlantic segment of the boundary between the African and Eurasian plates, the AGFZ is largely dominated by compressional forces between these converging (3.8 to 5.6 mm/a (0.15 to 0.22 in/year)) plates, but it is subject to a dynamic tectonic regime that also involves extension and
transform faulting. The
oceaniclithosphere in the area is directly related to the
opening of the North Atlantic Ocean and is one of the oldest preserved on Earth.[2]
The western end of the AGFZ, the
Azores Triple Junction on the
Mid-Atlantic Ridge (MAR), is where the North American, African, and Eurasian plates meet.[3] Spreading in the MAR is faster south of the AGFZ than north of it, which results in a transcurrent movement along the AGFZ at about 4 mm/a (0.16 in/year).[1] The eastern segment of the fault is complex and characterised by a series of seamounts and ridges separating the
Tores and
Horseshoe abyssal plains. The active compressional deformation in this segment is an extremely rare example of compression between two oceanic lithospheres.[1]
Plate tectonics
The Atlantic Ocean is surrounded by
passive margins with the exception of three subduction zones: the
Lesser Antilles Arc in the Caribbean, the
Scotia Arc in the South Atlantic, and the
Gibraltar Arc in the western
Mediterranean. The Gibraltar Arc is propagating westward into the Atlantic over an east-dipping oceanic slab (one of the remainders of the
Tethys Ocean). This subduction/
back-arc basin system is developing in front of the Alboran Block (under the
Alboran Sea) at a rate faster than that of the Africa-Iberia convergence. Consequently, this area is a rare case of a passive margin slowly being transformed into an
active margin.[4] The extension of this subduction system, known as the "allochthonous unit of the Gulf of Cadiz" (AUGC), marks the continuing propagation of the
Alpide belt into the Atlantic along the AGFZ.[5] In the context of the
Wilson Cycle, this suggests that the beginning of the closure of the Atlantic is taking place in front of the three Atlantic subduction zones.[4]
i. c. Ribeiro, Ana; p. s. Correia, Ana; Ribeiro, José R. (2020), "2 February 1816, an Overlooked North Atlantic M 8 Earthquake", Seismological Research Letters, 91 (5): 2912–2921,
Bibcode:
2020SeiRL..91.2912R,
doi:
10.1785/0220200201,
S2CID225211860