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Abigail?K.?BarkerEmail author Valentin?R.?Troll Juan?Carlos?Carracedo Peter?A.?Nicholls 《Contributions to Mineralogy and Petrology》2015,170(5-6):54
The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcano magmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma. The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral thermobarometry and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20–45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25–45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30–50 km. Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity. 相似文献
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Jordi Dachs Josep M. Bayona Scott W. Fowler Juan-Carlos Miquel Joan Albaigs 《Marine Chemistry》1998,60(3-4)
The different sources of lipid compounds present in sinking particles collected in a sediment trap mooring deployed in the Alboran Sea (SW Mediterranean) were elucidated using the molecular marker concept. A significant contribution of cyanobacterial lipids was identified based on the occurrence of a series of 3- and 5-methylalkanes and dimethylalkanes. Further evidence of cyanobacterial inputs was obtained by principal component analysis of all data showing diploptene and n-alkanes in the range C14–C22 clustered together with those branched alkanes. The use of methyl and dimethyl alkanes to trace cyanobacterial sources in the water column is proposed with advantage to sterols which are usually masked by phytoplanktonic sterols. The sterol distribution indicates phytoplankton as a major source with a contribution from heterotrophic zooplanktonic. Both fossil and biogenic sources can be contributors to the large unresolved complex mixture (UCM) found in these samples. 相似文献
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Valentin R. Troll Alejandro Rodriguez‐Gonzalez Frances M. Deegan Francisco Jos Perez‐Torrado Juan Carlos Carracedo Konstantinos Thomaidis Harri Geiger Fiona C. Meade 《Geology Today》2019,35(2):55-62
Gran Canaria, like most of the Canary Islands, shows evidence for young basaltic volcanism in the form of cinder cones and valley‐hugging lava flows. These landforms were of no particular use to the aboriginal population, nor to the subsequent Spanish settlers, and young lava flows and lava fields are still referred to as ‘malpaís’ (badlands) in the Canary Islands. In north‐west Gran Canaria, one such lava flow fills the bottom of a steep‐sided valley, which reaches the sea at the present day village of Agaete. The lava flow erupted c. 3030 ± 90 yr bp and displays a total length of ～ 11 km. At its distal end, just outside Agaete, it hosts one of Europe’s largest and most important pre‐historic burial sites constructed of volcanic rock: the Maipés necropolis. Over 700 pre‐historic tombs (or tumuli) constructed from the aa‐type clinker materials have been identified on top of the valley‐filling lava flow. The up to soccer‐ball sized vesicular clinker fragments are sufficiently low in density to provide abundant, workable basalt blocks for the construction of the tumuli, allowing the pre‐hispanic aboriginal population to create a large and magnificent ‘sacred ground’ in an otherwise barren landscape. 相似文献
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Juan‐Carlos Carracedo Francisco J. Perez‐Torrado Alejandro Rodriguez‐Gonzalez Raphaël Paris Valentin R. Troll Abigail K. Barker 《Geology Today》2015,31(4):146-152
In recent months the media have drawn attention to the Cape Verde archipelago, with particular focus on the island of Fogo, the only island presently active and with an eruption that began on 23 November 2014, finally ceasing on 7 February 2015. The Monte Amarelo conical shield forms most of the 476 km2 almost circular island of Fogo. After attaining a critical elevation of about 3500 m, the Monte Amarelo shield volcano was decapitated by a giant landslide that formed a caldera‐like depression (Cha das Caldeiras), which was subsequently partially filled by basaltic nested volcanism. This younger eruptive activity culminated in the construction of the 2829 m‐high Pico do Fogo stratocone, apparently entirely made of layers of basaltic lapilli. Continued growth of the Pico do Fogo summit eruptions was interrupted in 1750, most likely after the stratocone reached a critical height. Since then, at least eight eruptions have taken place inside the landslide depression at the periphery of the Pico do Fogo cone, including the 2014–2015 eruptive event. Strong geological similarities with the Canary Islands, 1400 km to the north, have been frequently noted, probably as a consequence of a common process of origin and evolution associated with a mantle hot‐spot. These similarities are particularly evident when comparing Fogo with the Teide Volcanic Complex on Tenerife, where a lateral collapse of the Las Cañadas stratovolcano also formed a large depression (the Caldera de Las Cañadas), now partially filled with the 3718 m‐high Teide stratocone. However, important geological differences also exist and probably relate to the contrasting evolutionary stages of both islands. The Las Cañadas volcano on Tenerife formed at a late post‐erosional stage, with predominantly evolved (trachyte and phonolite) magmas, while at Fogo basaltic volcanism is still dominant. 相似文献
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Hilary Clarke Valentin R. Troll Juan Carlos Carracedo 《Journal of Volcanology and Geothermal Research》2009,180(2-4):225
Phreatomagmatic activity results from the interaction of magma and external water during a volcanic eruption and is a frequent eruptive phenomenon worldwide. Such ‘fuel-coolant’ reactions change the eruptive dynamics, thus generating particles that reflect the degree of explosivity. Different eruptive phases may thus be identified from deposits, allowing us to reconstruct conditions that prevailed in the past and use these to predict the level of explosivity in a given geological setting in the future.A detailed study of the deposits from Montaña Los Erales, a 70 m-high Quaternary cinder cone belonging to a rift-related chain of vents in the Bandas del Sur region, in Southeast Tenerife, was undertaken. Field observations on excavated sections and SEM analysis of tephra suggest that the eruption style changed progressively from an initial phreatomagmatic phase, through a transitional stage, to one that was entirely Strombolian. To investigate the causes and the nature of these changes in eruptive style, products from each major unit were analysed for their morphology using hand specimen observations, secondary electron microscopy, backscatter electron microscopy, and reflected light microscopy to examine fragment size variation, fragment morphologies, vesicularity, and the level of secondary hydrous alteration (e.g. palagonitisation and zeolitisation). Study results demonstrate that the initial phase of activity was largely driven by magma–water interaction, where magma may have interacted with a lens of fresh ground- or surface water. With proceeding eruptive activity the water became exhausted, giving rise to an entirely Strombolian eruptive style.Examples of phreatomagmatic activity that occur on typical rift-related basaltic vent alignments are not infrequent in the Canary Islands. These vent systems usually erupt in Strombolian fashion, producing scoria and lava flows that do not generally extend far beyond the vent area. However, aligned feeders may intersect different strata, structural features, and different hydrological situations, thus giving rise to activity that is less predictable in setting, intensity, and duration. The occurrence of phreatomagmatism in an otherwise low-explosivity basaltic eruptive environment increases the need for awareness of the geo-hydrological situation in volcanically active areas. Studying the past eruptive history is therefore essential to derive realistic scenarios for future vulnerability evaluation and risk assessment, especially in densely populated areas like the Canary Islands. 相似文献
26.
The PESETA project makes a high-resolution integrated assessment of the effects of climate change in Europe in the following
impact categories: agriculture, river floods, coastal systems, tourism and human health. Many relevant methodological decisions
underlie the multi-disciplinary assessment, such as the selection of the climate scenarios and the economic valuation of the
physical impacts. The main purpose of this article is to document the methodological framework of the PESETA project, identifying
also where further research is required. How the different sources of uncertainty have been addressed in the project is explicitly
analysed, including the climate change scenarios and the various sectoral methodologies. 相似文献
27.
In recent months the media has been drawing attention to the possibility of a dangerous eruption of the Teide Volcano on Tenerife in the Canary Islands. Before accepting this prediction, which may well be detrimental to the tourist-based economy of the island, it would be wise to examine the evidence on which it is based. 相似文献
28.
Summary. The age of historical lava flows on the Canary Islands can be traced back at least to 1585 ad . During the last 400 years eruptions occurred at fairly regular intervals. The palaeomagnetic directions of these lavas record the ambient field direction with high precision so that an historical secular variation curve (SVC) can be constructed for the Canaries which closely resembles the curve registered at Paris. The SVC can be used as a dating tool for historical eruptions of unknown age and can probably be extended into the last 4000–5000 yr of recent volcanic activity on the Canaries. 相似文献
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