Reflection profiles characterize the structure and the upper Mesozoic to Cenozoic deposits of the Gulf of Ciidiz region. Two long ENE-WSW multichannel seismic lines (ca. 400-500 km long) are analyzed to study the evolution of the area from the continental shelf to the Horseshoe and Seine abyssal plains. The huge allochthonous deposits emplaced in this region (the so called "Olistostrome" of the Gulf of Cadiz) are described in terms of three different domains on the basis of the seismic architecture, the main tectonic features and the nature of the basement, oceanic or continental. The eastern domain extends along the continental shelf and upper and middle slope and corresponds to the offshore extension of the Betic -Rifean external front. It is characterized by salt and shale nappes later affected by extensional collapses. The central domain develops along the lower slope between the Betic-Rifean front and the abyssal plains and is characterized by a change in dip of the allochthonous basal surface and the basement. The allochthonous masses were emplaced by a combined gravitational and tectonic mechanism.The nOlihern boundary of this domain is marked by the occurrence of an outstanding WNW -ESE-trending thrust fault with a strike-slip component, termed here as the Gorringe-Horseshoe fault. The westernmost domain corresponds to the abyssal plains, where the distal emplacement of the allochthonous body takes place; it is characterized by thrust faults affecting both the sedimentary cover and the oceanic basement. The allochthonous masses show a less chaotic character and the thickness decreases notably. These domains represent different evolutionary steps in the mechanisms of emplacement of the allochthonous units. The eastern domain of the allochthonous units was emplaced as part of the pre-Messinian orogenic wedge related to the collision that gave rise to the Betic-Rifean Belt, whereas the allochthonous wedge of the central and western domains were emplaced later as a consequence of the NE-SW late Miocene compression that continues in present times.

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A new morphosedimentary map of the Gulf of Cadiz is presented, showing the contourite depositional system on the gulf's middle slope. This map is constructed from a broad database provided by the Spanish Research Council and the U.S. Naval Research Laboratory. Our map shows that this contourite depositional system comprises five morphosedimentary sectors: (1) proximal scour and sand ribbons; (2) overflow sedimentary lobe; (3) channels and ridges; (4) contourite deposition; and (5) submarine canyons. The Gulf of Cadiz contourite depositional system stems directly from the interaction between Mediterranean Outflow Water and the seafloor; its morphosedimentary sectors are clearly related to the systematic deceleration of the Mediterranean Outflow Waters westward branches, bathymetric stress on the margin, and the Coriolis force. The slope's depositional system can be considered as a mixed contourite and turbidite system, i.e., a detached combined drift and fan.

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We report precursory geophysical, geodetic, and geochemical signatures of a new submarine volcanic activity observed off the western coast of El Hierro, Canary Islands. Submarine manifestation of this activity has been revealed through acoustic imaging of submarine plumes detected on the 20-kHz chirp parasound subbottom profiler (TOPAS PS18) mounted aboard the Spanish RV Hespérides on June 28, 2012. Five distinct "filament-shaped" acoustic plumes emanating from the flanks of mounds have been recognized at water depth between 64 and 88 m on a submarine platform located NW El Hierro. These plumes were well imaged on TOPAS profiles as "flares" of high acoustic contrast of impedance within the water column. Moreover, visible plumes composed of white rafts floating on the sea surface and sourcing from the location of the submarine plumes were reported by aerial photographs on July 3, 2012, 5 days after acoustic plumes were recorded. In addition, several geophysical and geochemical data support the fact that these submarine vents were preceded by several precursory signatures: (i) a sharp increase of the seismic energy release and the number of daily earthquakes of magnitude ≥2.

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