Jesús Rivera

Construction of an oceanic island: Insights from the El Hierro (Canary Islands) 2011–2012 submarine volcanic eruption

Eight consecutive swath bathymetry data sets were obtained to monitor the submarine eruption that occurred from 10 October 2011 to 5 March 2012 south of El Hierro Island in the Canary Islands. An increase in seismic activity since July 2011 preceded the onset of the eruption, which was marked by seismic tremor and stained waters. The first bathymetry, 15 d after the eruption started, depicts a cone topping at 205 m depth, growing on a preexisting valley. Recurrent mapping shows changes in the morphology and depth of the cone, allowing us to identify collapses and calculate eruptive volumes and rates, which peaked at 12.7 × 10 6 m 3 d −1 of non–dense rock equivalent (NDRE) on 29–30 October. The final cone consists of at least four vents along a north-northwest–south-southeast lineation, with the shallowest summit at 89 m depth. The total accumulated volume was 329 × 10 6 NDRE m 3 , of which one-third formed the cone. Similar cones have been identified on the submerged flanks of the island, with volumes ranging from 6 to >1000 × 10 6 NDRE m 3 . As in many other volcanic islands, large-scale landslides play an important role in the evolution of El Hierro. A giant flank landslide (El Golfo, 13–134 ka, 150–180 km 3 ) mobilized, in a single event, a volume equivalent to 450–550 eruptions of the size of the reported one, showing striking differences in the construction and destruction rates of the island. This study is relevant for future monitoring programs and geohazard assessment of new submarine eruptions.

A submarine volcanic eruption leads to a novel microbial habitat

Submarine volcanic eruptions are major catastrophic events that allow investigation of the colonization mechanisms of newly formed seabed. We explored the seafloor after the eruption of the Tagoro submarine volcano off El Hierro Island, Canary Archipelago. Near the summit of the volcanic cone, at about 130 m depth, we found massive mats of long, white filaments that we named Venus’s hair. Microscopic and molecular analyses revealed that these filaments are made of bacterial trichomes enveloped within a sheath and colonized by epibiotic bacteria. Metagenomic analyses of the filaments identified a new genus and species of the order Thiotrichales, Thiolava veneris. Venus’s hair shows an unprecedented array of metabolic pathways, spanning from the exploitation of organic and inorganic carbon released by volcanic degassing to the uptake of sulfur and nitrogen compounds. This unique metabolic plasticity provides key competitive advantages for the colonization of the new habitat created by the submarine eruption. A specialized and highly diverse food web thrives on the complex three-dimensional habitat formed by these microorganisms, providing evidence that Venus’s hair can drive the restart of biological systems after submarine volcanic eruptions.

Bathymetry of a new-born submarine volcano: El Hierro. Canary Islands

We present here a bathymetric map of a new underwater volcano which began its growth on 10 October 2011 to the south of El Hierro Island (Canary Is., Spain). The map scale is 1:25,000 and the map covers 210.9 sq. km. In July 2011, the seismic monitoring network of Spanish National Geographic Institute (IGN), began to detect an increase in low-intensity earthquakes around El Hierro Island along with ground deformation. This seismic crisis culminated on 10th October with a submarine eruption 2 km south of the small port of La Restinga, and lasted until March 2012 when IGN determined the end of the eruption process. After eight surveys monitoring the morphological and bathymetric evolution during the eruptive phase that ended in March 2012, Spanish Oceanographic Institute and the Hydrographic Institute of the Navy, carried out a survey from the 6th to the 8th of December 2012 to map the bathymetric and morphologic situation after the 2011–2012 eruptive period. The map presented here is based on full seafloor coverage by multibeam swath data echosounder carried out when the submarine volcano was in a quiet phase, using a grid mesh size of 12 × 12 meters.

Subaqueous Dunes Over Sand Ridges on the Murcia Outer Shelf

Multibeam swath bathymetry, high-resolution seismic data and sediment samples were used to characterize a field of sand ridges and subaqueous dunes on the outer Murcia continental shelf (western Mediterranean Sea). Sand ridges are 1.5–3 m high and show a predominant E-W orientation oblique to the present-day shoreline. High-resolution seismic data reveal a backstepping stacking pattern of high-angle clinoforms dipping towards the southwest, interpreted as buried sand bodies. Subaqueous dunes have a mean height of 0.3 m and appear superimposed on the sand ridges showing a NW-SE orientation oblique to the ridges. They are composed of sandy sediments and display asymmetric morphology, with the lee side towards the southwest. Ridge and dune asymmetry and internal structure are indicative of long-term sediment transport towards the southwest. At present, dune migration rates deduced from repeated bathymetric surveys indicate that the dunes remain stationary or migrate at very low rates on a decadal scale.

Morphometry of Concepcion Bank: Evidence of Geological and Biological Processes on a Large Volcanic Seamount of the Canary Islands Seamount Province.

Concepcion Bank is the largest seamount in the Canary Islands Seamount Province (CISP), an oceanic area off NW Africa including 16 main seamounts, the Canaries archipelago and the Selvagens subarchipelago. The Bank is located 90 km northeast of Lanzarote Island and has been identified as a candidate Marine Protected Area (MPA) to be included in the Natura 2000 network. A compilation of complementary datasets consisting of multibeam bathymetry, TOPAS seismic reflection profiles, side scan sonar sonographs, Remotely Operated Vehicle video records and seafloor samples allowed describing in detail and ground truthing the submarine landforms and bioconstructions exhibited by the bank. The Concepcion Bank presently rises up to 2,433 m above the adjacent seafloor and exhibits two main domains: an extensive summit plateau and steep flanks. The sub-round summit plateau is 50km by 45 km and ranges from 158 to 1,485 m depth. The steep flanks that bound it descend to depths ranging between 1,700 and 2,500 m and define a seamount base that is 66km by 53 km. This morphology is the result of constructive and erosive processes involving different time scales, volumes of material and rates of change. The volcanic emplacement phase probably lasted 25–30 million years and was likely responsible for most of the 2,730 km3 of material that presently form the seamount. Subsequently, marine abrasion and, possibly, subaerial erosion modulated by global sea level oscillations, levelled the formerly emerging seamount summit plateau, in particular its shallower (<400 m), flatter (<0.5°) eastern half. Subsidence associated to the crustal cooling that followed the emplacement phase further contributed the current depth range of the seamount. The deeper and steeper (2.3°) western half of Concepcion Bank may result from tectonic tilting normal to a NNE-SSW fracture line. This fracture may still be expressed on the seafloor surface at some scarps detected on the seamount’s summit. Sediment waves and cold-water coral (CWC) mounds on the bank summit plateau are the youngest features contributing to its final shaping, and may be indicative of internal wave effects. Numerous submarine canyons generally less than 10 km in length are incised on the bank’s flanks. The most developed, hierarchized canyon system runs southwest of the bank, where it merges with other canyons coming from the southern bulges attached to some sections of the seamount flanks. These bulges are postulated as having an intrusive origin, as no major headwall landslide scars have been detected and their role as deposition areas for the submarine canyons seems to be minor. The results presented document how geological processes in the past and recent to subrecent oceanographic conditions and associated active processes determined the current physiography, morphology and sedimentary patterns of Concepcion Bank, including the development and decline of CWC mounds The setting of the seamount in the regional crustal structure is also discussed.

Cold-Water Coral Colonization of Alboran Sea Knolls, Western Mediterranean Sea

Publisher Summary The Alboran Sea is the westernmost basin of the Mediterranean Sea and represents a basin 350 km long and 150 km wide, with water depths between 0 and 2,000 m. The Alboran Sea is characterized by highly dynamic and variable water masses that make it one of the most productive areas in the oligotrophic Mediterranean Sea. Hydrodynamic features occur across all time and length scales, such as tidal motion, strong baroclinic jets, large-scale gyres, mesoscale eddies, upwelling regions, and frontal zones, all with important implications on the dynamics of plankton and benthic ecosystems [3]. The strong surface inflow of Atlantic water through the Strait of Gibraltar, known as the Atlantic Jet, maintains two semipermanent anticyclonic gyres consisting of a mixture of different proportions of Mediterranean and Atlantic waters that change in sympathy with tidal cycles. The knolls in the Alboran Sea are affected by benthic trawl fisheries, evidenced by trawl marks and lost fishing gear observed in the study area. Overall, the naturalness of the study area is considered to be modified. The topography of the Alboran Basin seafloor is characterized by pinnacles, knolls, banks, ridges, and troughs as a direct expression of the Pliocene-Quaternary compressive tectonic regime. Colonization in the past and present does not correspond to any particular side of the knoll flanks; hence, it appears there is no eznhanced source of nutrients nor any increased pressure related to sedimentation from any particular direction in the study area. Upscaling from detailed habitat maps of knolls to basin-wide predictive habitat maps reveals various potential CWC habitats that are not yet surveyed and might lead to new discoveries of relict and living CWC ecosystems in the basin.

Corrigendum: A submarine volcanic eruption leads to a novel microbial habitat

This corrects the article DOI: 10.1038/s41559-017-0144