Search results for "volcan"
showing 10 items of 899 documents
Testing the hypothesis of post-volcanic missing rings in temperature sensitive dendrochronological data
2013
a b s t r a c t The precise, annual dating control, inherent to dendrochronology, has recently been questioned through a combined analysis of tree-growth and coupled climate models (Mann et al. (2012; hereafter MAN12)) suggesting single tree-rings in temperature limited environments are missing following large volcanic events. We test this hypothesis of missing, post-volcanic rings by using a compilation of maximum late- wood density (MXD) records that are typically used for reconstructing temperature and the detection of volcanic events, together with a unique set of long instrumental station data from Europe reaching back into the early 18th century. We investigate the temporal coherence …
Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD
2016
Societal upheaval occurred across Eurasia in the sixth and seventh centuries. Tree-ring reconstructions suggest a period of pronounced cooling during this time associated with several volcanic eruptions. Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe1,2 and Asia3,4. In particular, the sixth century coincides with rising and falling civilizations1,2,3,4,5,6, pandemics7,8, human migration and political turmoil8,9,10,11,12,13. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. Here we use tree-ring…
Evidence of tephra reworking in loess based on 2D magnetic susceptibility mapping: A case study from Rocourt, Belgium
2016
Abstract In this article, a new and original approach to characterize tephra layers based on high resolution magnetic susceptibility (MS) mapping is applied to the tephra deposits of Rocourt (Belgium). A series of MS maps of selected sections show the 3D morphology of tephra horizons, including local dip and reworked structures of the Rocourt and Eltville tephras, proven by chemical analyses of phenocrysts. At Rocourt, tephras are observed in loess which is an excellent material for testing the efficiency of the magnetic susceptibility mapping of tephra deposits. We also attempted to locate the volcanic source of the Eltville tephra based on the spatial analysis of the thickness of deposits…
Climatic ups and downs in a disturbed Jurassic world.
2011
4 pages; International audience; The tropical, warm, and equable climate of the Jurassic world is regularly challenged by geoscientists, especially since oxygen isotopes ( 18O) of fossil hardparts have been used to reconstruct the paleotemperature history of seawater. By applying the innovative “SiZer” (significant zero crossings of the derivatives) statistical approach to a newly compiled 18O database for the Jurassic, we demonstrate the occurrence of major and multiscale 18O changes mainly related to climate disturbances. For the first time, two long-term anomalies in 18O are identified during the Toarcian and the Late Jurassic, in conjunction with intensive volcanism in large igneous pro…
How ocean acidification can benefit calcifiers.
2017
Reduction in seawater pH due to rising levels of anthropogenic carbon dioxide (CO2) in the world's oceans is a major force set to shape the future of marine ecosystems and the ecological services they provide [1,2]. In particular, ocean acidification is predicted to have a detrimental effect on the physiology of calcifying organisms [3]. Yet, the indirect effects of ocean acidification on calcifying organisms, which may counter or exacerbate direct effects, is uncertain. Using volcanic CO2 vents, we tested the indirect effects of ocean acidification on a calcifying herbivore (gastropod) within the natural complexity of an ecological system. Contrary to predictions, the abundance of this cal…
Staying alive on an active volcano: 80 years population dynamics of Cytisus aeolicus (Fabaceae) from Stromboli (Aeolian Islands, Italy)
2020
Abstract Cytisus aeolicus is a narrow endemic species restricted to the Aeolian archipelago (SE Tyrrhenian Sea, Italy) and it is one of the most evolutionarily isolated plants in the Mediterranean flora. Historical and literature data suggest that both metapopulations and isolated individuals of C. aeolicus are gradually shrinking. Field investigations and drone images demonstrate that the C. aeolicus metapopulation from Stromboli experienced a strikingly fast increase during the last decades. As of 2019, more than 7000 ± 3000 mature individuals occur on Stromboli, i.e. 14 to 20 times more than those counted during the last census, 25 years ago. The diachronic analysis of aerial photos conc…
Species–area relationship and small-island effect of vascular plant diversity in a young volcanic archipelago
2021
International audience; Aims: Aeolian islands form an active volcanic archipelago. By using updated vascular plant checklists for islands and islets, we tested four hypotheses: (i) Island speciesarea relationship (ISAR) of alien species has lower c-and higher z-values than native species, (ii) islands with active volcanoes have lower species richness than expected for native and alien species, (iii) ISAR of native species shows lower c-and higher z-values than ISARs of Mediterranean land bridge archipelagos and (iv) species richness of smaller islets is independent of area.Location: Aeolian Archipelago, Mediterranean Basin.Taxon: Vascular plants, identified and named according to the Flora …
Cinderella's helping pigeons of the microbial world: The potential of testate amoebae for identifying cryptotephra
2016
Cryptotephra (particles <125μm) is a key record for monitoring past and current volcanic activity. However, its extraction from the host sediment and analysis is often long and difficult because of its small size. Finding a simple method to extract cryptotephra from environmental samples would therefore make its analysis much easier. We hypothesized that arcellinid testate amoebae may hold such a potential. These free-living shelled protists are among the earliest microorganisms to colonize volcanic tephra, and build their shell by agglutinating minerals from their environment. We analyzed by X-ray Spectrometry the mineral signature of tephra from the 2011 Puyehue-Cordon Caulle Volcanic Com…
Temporal fluctuations in seawater pCO2 may be as important as mean differences when determining physiological sensitivity in natural systems
2015
AbstractMost studies assessing the impacts of ocean acidification (OA) on benthic marine invertebrates have used stable mean pH/pCO2 levels to highlight variation in the physiological sensitivities in a range of taxa. However, many marine environments experience natural fluctuations in carbonate chemistry, and to date little attempt has been made to understand the effect of naturally fluctuating seawater pCO2 (pCO2sw) on the physiological capacity of organisms to maintain acid–base homeostasis. Here, for the first time, we exposed two species of sea urchin with different acid–base tolerances, Paracentrotus lividus and Arbacia lixula, to naturally fluctuating pCO2sw conditions at shallow wat…
Geochemical survey of Levante Bay, Vulcano Island (Italy), a natural laboratory for the study of ocean acidification
2013
Abstract Shallow submarine gas vents in Levante Bay, Vulcano Island (Italy), emit around 3.6t CO2 per day providing a natural laboratory for the study of biogeochemical processes related to seabed CO2 leaks and ocean acidification. The main physico-chemical parameters (T, pH and Eh) were measured at more than 70 stations with 40 seawater samples were collected for chemical analyses. The main gas vent area had high concentrations of dissolved hydrothermal gases, low pH and negative redox values all of which returned to normal seawater values at distances of about 400 m from the main vents. Much of the bay around the vents is corrosive to calcium carbonate; the north shore has a gradient in s…