Volcano Centre Research Articles

Exploring marine zooplankton dynamics through carbon stable isotope signatures in a recently marine submarine volcano

Submarine emissions of gases from hydrothermal vents alter the surrounding chemical environment, influencing species responses to the resulting environmental gradients. The 2011 underwater eruption of the Tagoro volcano off the coast of El Hierro in the Atlantic Ocean changed the physical and chemical conditions, impacting the distribution of pelagic fauna. Post-eruptive stages from 2013 to 2018 revealed changes in both benthic and pelagic communities, with continuous eruptions further affecting local carbon cycle through shifts in nutrient concentrations and isotopic composition. The lowest δ13C values in zooplanktonic primary consumers were found in areas directly influenced by the Tagoro submarine volcano. Although the mixing model results show that phytoplankton is the primary carbon source for copepods, contributing an average of 28.3% of their carbon, magmatic CO2 and seawater dissolved inorganic carbon each account for approximately 17–18%. The isotopic signatures reveal a gradient of enrichment in copepods, reflecting the influence of inorganic nutrient and gas emissions from the volcano's centre to its periphery within the marine ecosystem. This data is useful for understanding the worldwide significance of environmental stressors such as volcanic eruptions on marine organisms.

Rheological properties and ages of lava flows on Alba Mons, Mars

We present the results of our studies of the rheological properties and ages on Alba Mons lava flows. Previous studies have shown that the rheology of lava flows, such as yield strength and viscosity, as well as external parameters affecting flow characteristics, such as effusion rate and eruption duration can be derived by remotely sensed dimension measurements. The calculations made in this study are based on images obtained from the Context Camera (CTX) on board of NASA's Mars Reconnaissance Orbiter (MRO) as well as data from the Mars Orbiter Laser Altimeter (MOLA) on NASA's Mars Global Surveyor (MGS). Absolute model ages (AMAs) have been derived by performing crater size-frequency distribution (CSFD) measurements on CTX images. The main objectives of this investigation are not only the calculation of the rheological properties and ages, but also the analysis of possible correlations between the rheologies, ages and distances of the flows to the volcano's center. A comparison of the rheological properties of the investigated lavas with those reported for flows on other planetary bodies was also performed. The aim of the study is a better insight into the history of one of the largest volcanoes in the Solar System. We provide new information about the formation and composition of the volcano's lava flows, whether they changed over time, and until when Alba Mons has been active.In total, 29 lava flows close to the summit of Alba Mons were mapped and measured. The calculated yield strengths are 2.79 × 103 Pa on average, ranging from 4.00 × 102 Pa to 9.61 × 103 Pa. We found effusion rates between 46 m3 s−1 and 1528 m3 s−1 with an average effusion rate of 636 m3 s−1. The derived viscosity is on the order of 1.04 × 107 Pa s with values between 1.27 × 105 Pa s and 1.0 × 108 Pa s. The lavas have erupted over a period of 11 to 223 days, with an average eruption duration of 68 days. The rheological properties derived in this investigation are very similar to those of other volcanic regions on Mars, especially Elysium Mons and Elysium Planitia. However, they differ from calculated rheologies of previous studies of venusian lavas and lunar lava flows. Based on the derived yield strength and viscosity values, the composition of the lava flows can be inferred as basaltic/basaltic-andesitic, which is analog to terrestrial basaltic or andesitic a'a lava flows. Significant correlations between the rheological properties and the distance to Alba Mons' center have not been found. AMAs could be derived for 14 of the 29 lava flows investigated, because 15 lava flows have either reached the state of equilibration or have too few impact craters to derive reliable model ages. The AMAs range from 130 ± 40 Ma to 810 ± 60 Ma. The results indicate a late volcanic activity at Alba Mons. Correlations between the AMAs and distance to the volcano's center, as well as between the rheological properties and AMAs were not observed.

Vegetation cover at the Maguntan mud volcano (Sakhalin Island, Russia): species composition and spatial distribution

Mud volcano vegetation is not well-studied even in comparison with that of geothermal areas. Mud volcanoes provide opportunities to study the formation of the spatial and species structure of vegetation cover in distinct conditions, showing the trends in vegetation succession. The mud fields of the Maguntan mud volcano (Sakhalin, Russia) are cool, not warm, and their mud fluids have high salinity and alkalinity. In the 20th century some local endemic taxa were found at this place: Artemisia limosa, Gentianella sugawarae, Primula sachalinensis and Deschampsia tzvelevii. I identified nine plant communities and analyzed floristic richness, vegetation cover and endemism rate using data from 185 1 m × 1 m quadrats. The salinity decreases with distance from the volcano's main eruptive center. The total plant cover, number of plant species, and floristic richness increase with the distance from the volcano's center. Endemic taxa including the local endemic grass species Deschampsia tzvelevii are located in young mud substrates. Detrended correspondence analysis showed that the plant communities are arranged along a stress gradient. The spatial distribution of plant communities may be interpreted via succession dynamics.

The use of rotational invariants for the interpretation of marine CSEM data with a case study from the North Alex mud volcano, West Nile Delta

Submarine mud volcanos at the seafloor are surface expressions of fluid flow systems within the seafloor. Since the electrical resistivity of the seafloor is mainly determined by the amount and characteristics of fluids contained within the sediment's pore space, electromagnetic methods offer a promising approach to gain insight into a mud volcano's internal resistivity structure. To investigate this structure, we conducted a controlled source electromagnetic experiment, which was novel in the sense that the source was deployed and operated with a remotely operated vehicle, which allowed for a flexible placement of the transmitter dipole with two polarization directions at each transmitter location. For the interpretation of the experiment, we have adapted the concept of rotational invariants from land-based electromagnetics to the marine case by considering the source normalized tensor of horizontal electric field components. We analyse the sensitivity of these rotational invariants in terms of 1-D models and measurement geometries and associated measurement errors, which resemble the experiment at the mud volcano. The analysis shows that any combination of rotational invariants has an improved parameter resolution as compared to the sensitivity of the pure radial or azimuthal component alone. For the data set, which was acquired at the ‘North Alex’ mud volcano, we interpret rotational invariants in terms of 1-D inversions on a common midpoint grid. The resulting resistivity models show a general increase of resistivities with depth. The most prominent feature in the stitched 1-D sections is a lens-shaped interface, which can similarly be found in a section from seismic reflection data. Beneath this interface bulk resistivities frequently fall in a range between 2.0 and 2.5 Ωm towards the maximum penetration depths. We interpret the lens-shaped interface as the surface of a collapse structure, which was formed at the end of a phase of activity of an older mud volcano generation and subsequently refilled with new mud volcano sediments during a later stage of activity. Increased resistivities at depth cannot be explained by compaction alone, but instead require a combination of compaction and increased cementation of the older sediments, possibly in connection to trapped, cooled down mud volcano fluids, which have a depleted chlorinity. At shallow depths (≤50 m) bulk resistivities generally decrease and for locations around the mud volcano's centre 1-D models show bulk resistivities in a range between 0.5 and 0.7 Ωm, which we interpret in terms of gas saturation levels by means of Archie's Law. After a detailed analysis of the material parameters contained in Archie's Law we derive saturation levels between 0 and 25 per cent, which is in accordance with observations of active degassing and a reflector with negative polarity in the seismics section just beneath the seafloor, which is indicative of free gas.

Trophic specialisation of metazoan meiofauna at the Håkon Mosby Mud Volcano: fatty acid biomarker isotope evidence

We report the results of a detailed investigation on the trophoecology of two dominant meiofaunal species at the Hakon Mosby Mud Volcano (HMMV), a deep-sea cold methane-venting seep. Analyses of fatty acids (FAs) and their stable carbon isotopes were used to determine the importance of chemosynthetic nutritional pathways for the dominant copepod species (morphologically very similar to Tisbe wilsoni) inhabiting the volcano's centre and the abundant nematode Halomonhystera disjuncta from the surrounding microbial mats. The strong dominance of bac- terial biomarkers (16:17c, 18:17c and 16:18c) coupled with their individual light carbon isotopes signatures ( 13 C ranging from i52 to i81‰) and the lack of symbiotic relationships with prokaryotes (as revealed by molecular analyses and Xuorescent in situ hybridisation) indicated that chemosynthetically derived carbon constitutes the main diet of both species. However, the copepod showed a stronger reliance on the utilisation of methanotrophic bacte- ria and contained polyunsaturated FAs of bacterial origin (20:53 and 22:63 with isotope signatures 13 C< i80‰). Instead, the FA proWles of H. disjuncta suggested that sulphide-oxidising bacteria constituted the main diet of this nematode. Therefore, HMMV can be regarded as a per- sistent deep-sea cold seep, allowing a chemosynthesis- based trophic specialisation by the dominant meiofaunal species inhabiting its sediments. The present investigation, through the determination of the fatty acid proWles, pro- vides the Wrst evidence for trophic specialisation of meiofa- una associated with sub-habitats within a cold seep.

Meiobenthos at the Arctic Håkon Mosby Mud Volcano, with a parental-caring nematode thriving in sulphide-rich sediments

Hakon Mosby Mud Volcano (HMMV, SW Barents Sea slope, 1280 m) is one of the numerous cold methane-venting seeps existing along the continental margins. Analyses of video- guided core samples revealed extreme differences in the diversity and density of the metazoan meiobenthic communities associated with the different sub-habitats (centre, microbial mats, Pogonophora field, outer rim) of this mud volcano. Diversity was lowest in the sulphidic, microbial mat sediments that supported the highest standing stock, with unusually high densities (11 000 ind. 10 cm -2 ) of 1 nematode species related to Geomonhystera disjuncta. Stable carbon isotope analyses revealed that this nematode species was thriving on chemosynthetically derived food sources in these sediments. Ovoviviparous reproduction has been identified as an important adaptation of parents securing the survival and development of their brood in this toxic environment. The proliferation of this single species in exclusive association with free-living, sulphide-oxidising bacteria (Beggiatoa) indicates that its dominance is strongly related to trophic specialisation, evidently uncommon among the meiofauna. This chemoautotrophic association was replaced by copepods in the bare, sulphide- free sediments of the volcano's centre, dominated by aerobic methane oxidation as the chemosyn- thetic process. Copepods and nauplii reached maximum densities and dominance in the volcano's centre (500 ind. 10 cm -2 ). Their strongly depleted carbon isotope signatures indicated a trophic link with methane-derived carbon. This proliferation of only selected meiobenthic species supported by chemosynthetically derived carbon suggests that, in addition to the sediment geochemistry, the asso- ciated reduced meiobenthic diversity may equally be related to the trophic resource specificity in HMMV sub-habitats.

Growth and collapse of Waianae Volcano, Hawaii, as revealed by exploration of its submarine flanks

Wai‘anae Volcano comprises the western half of O‘ahu Island, but until recently little was known about the submarine portion of this volcano. Seven new submersible dives, conducted in 2001 and 2002, and multibeam bathymetry offshore of Wai‘anae provide evidence pertaining to the overall growth of the volcano's edifice as well as the timing of collapses that formed the Wai‘anae slump complex. A prominent slope break at ∼1400 mbsl marks the paleoshoreline of Wai‘anae at the end of its shield‐building stage and wraps around Ka‘ena Ridge, suggesting that this may have been an extension of Wai‘anae's northwest rift zone. Subaerially erupted tholeiitic lavas were collected from a small shield along the crest of Ka‘ena Ridge. The length of Wai‘anae's south rift zone is poorly constrained but reaches at least 65 km on the basis of recovered tholeiite pillows at this distance from the volcano's center. Wai‘anae's growth was marked by multiple collapse and deformation events during and after its shield stage, resulting in the compound mass wasting features on the volcano's southwest flank (Wai‘anae slump complex). The slump complex, one of the largest in Hawai‘i, covering an area of ∼5500 km2, is composed of several distinct sections on the basis of morphology and the lithologies of recovered samples. Two dives ascended the outer bench of the slump complex and collected predominantly low‐S tholeiites that correlate with subaerial lavas erupted early during the volcano's shield stage, from 3.9 to 3.5 Ma. Pillow lavas from the outer bench have Pb, Sr, and Nd isotopic values that overlap with previously published subaerial Wai‘anae lavas. On the basis of the compositions of the recovered samples, the main body of the slump complex, as represented by the outer bench, probably formed during and shortly after the early shield stage. To the southwest of the outer bench lies a broad debris field on the seafloor, interpreted to have formed by a catastrophic collapse event that breached the outer bench. A dive within the debris field recovered subaerially derived volcaniclastic rocks; analyzed glasses are tholeiitic and resemble early shield stage compositions. The breach may have then been filled by slumping material from the main volcanic edifice. Finally, atop the northern main body of the slump is a rotated landslide block that detached from the proximal part of Ka‘ena Ridge after the volcano's late shield stage (3.2 to 3.0 Ma). From the inner scarp of this block we recovered subaerially erupted tholeiitic pillow breccias and hyaloclastites that are systematically higher in alkalis and more fractionated than those collected from the outer bench. These rocks correlate compositionally with late shield‐stage subaerial Kamaile‘unu lavas. None of the collected slump complex samples correlate with alkalic subaerial postshield lavas. Volcaniclastic rocks and glass disseminated in pelagic sediment, collected from north of Ka‘ena Ridge, originated from Wai‘anae's postshield stage and Ko‘olau's shield stage, respectively.

Scientific Serials

American Journal of Science, October.—A dissected volcanic mountain; some of its revelations, by James D. Dana. Here the author returns to the subject of Tahiti, largest of the Society Islands, already described by him in 1850 from materials supplied by the Wilkes Exploring Expedition of 1839. The old cone, some 7000 feet high, is now a dissected mountain, with valleys cut profoundly into its sides, and laying bare the centre to a depth of from 2000 to nearly 4000 feet below the existing summit. As shown on the accompanying map, the valleys, due to erosion, are so crowded on one another, that the dissection is complete, thus disclosing the inner structure of a great volcanic mountain. The interior is shown to be composed, not of lava-beds, there being no horizontal lines, but of imperfect columnar formations, rising vertically in the unstratified mass quite to the summit. The uniform massiveness through so great a height at the volcano's centre is attributed to the cooling of continuously liquid lava in the region of the great central conduit of the cone. A comparative study of Mauna Loa (Hawaii), shows that such a massive central structure is a common feature of the greater volcanic mountains, the extremely slow cooling process under great pressure causing the lava to solidify into a compact crystalline rock, and often into a coarsely crystalline rock.—Origin of the ferruginous schists and iron ores of the Lake Superior region, by R. D. Irving. Rejecting the igneous theory, now held by few, the writer, after a careful survey of the whole field, concludes that these rocks were once carbonates analogous to those of the coal-measures, which by a process of silicification were transformed into the various kinds of ferruginous formations now occurring in this region.—Further notes on the artificial lead silicate from Bonne Terre, Montana, by H. A. Wheeler. An analysis of this interesting substance, which was found under the hearth of an old reverberatory roasting-furnace, yielded 73.66 PbO, 17.11 SiO2, NiO 3.06 (coarse crystals), 72.93 PbO, 18.51 SiO2, and smaller quantities of nickel, cobalt, and other ingredients.—Limonite pseudomorphs after pyrite, by John G. Meem. The paper gives a snort account of the pseudomorphs occurring in Rockbridge County, Virginia, where they are associated with Lower Silurian limestones. These crystals, varying in colour from a very light to a very dark brown, and sometimes almost black, are hydrous, and yield a yellow powder, showing them to be limonite, most commonly of octahedral form.—Note on the hydro-electric effect of temper in case of steel, by C. Barus and V. Strouhal. The object of this inquiry is to determine directly the carbon relations of steel as a function of the temperature (0° to 400°, 400° to 1000°) and of the time of annealing, with full reference to the physical occurrences observed in the first and second phases of the phenomenon.—On the crystalline structure of iron meteorites, by Oliver Whipple Huntingdon. It is shown that the usual classification of these meteorites into octahedral and cubic crystals cannot be natural or fundamental. A careful examination of the large collection belonging to Harvard College, containing types of all the characteristic meteorites of this class, leads to the conclusion that masses of meteoric iron are cleavage crystals, broken off probably by impact with the air, and showing cleavages parallel to the planes of all three fundamental forms of the regular system (octahedron, cube, and dodecahedron); further, that the Widmanstättian figures and Neumann lines themselves are sections of planes parallel to these same forms, exhibited in every gradation from the broadest bands to the finest markings, with no natural break, the features of von Widmanstätten's figures being, moreover, due to the eliminations of impurities during the process of crystallisation.—A new meteoric iron from Texas, by W. Earl Hidden. The specimen here described and illustrated was discovered by Mr. C. C. Cusick on June 10, 1882, near Fort Duncan, Maverick County, Texas. It weighs over 97 pounds, is quite soft, being easily cut with a knife, and consists of iron 94.90; nickel and cobalt, 4.87; phosphorus, 0.25, with traces of sulphur and carbon; specific gravity, 7.522.—On pseudomorphs of garnet from Lake Superior and Salida, Colorado, by S. L. Penfield and F. L. Sperry. The Lake Superior specimen is essentially an iron alumina garnet, with formula Fe2Al2Si3O12. That of Colorado is higher in protoxides and water, the increase being perhaps due to the presence of ripidolite.—Further notes on the meteoric iron from Glorieta Mount, New Mexico, by George F. Kunz.—On the Brookite from Magnet Cove, Arkansas, by Edward S. Dana. These crystals, first described in 1846 by Shepard under the name of arkansite, are especially remarkable for the great variety of their forms, which is most unusual for crystals occurring in the same locality.