Stratigraphy, structure and geochronology of the Las Cañadas caldera (Tenerife, Canary Islands)

1994 ◽  
Vol 131 (6) ◽  
pp. 715-727 ◽  
Author(s):  
J. Martí ◽  
J. Mitjavila ◽  
V. Araña
Keyword(s):  
Caldera Collapse ◽  
Volcanic Complex ◽  
Caldera Wall ◽  
Magma Chambers ◽  
Basaltic Magmas ◽  
History Of ◽  
Northern Side ◽  
Geological Observation ◽  
Volcanic Cycles

AbstractAfter a long period of subaerial fissure-fed extrusions of basaltic magmas (∼ 12 to > 3 Ma) volcanic activity was then concentrated in the central part of Tenerife. Phonolitic magma chambers formed and a central volcanic complex was constructed (the Las Canadas edifice). The formation of a large depression (the Las Canadas caldera) truncated the top of the edifice. The active twin strato-cones Teide—Pico Viejo are sited in this depression. The history of the Las Canadas caldera and edifice are established from stratigraphy, geochronology (K—Ar dates) and volcanological studies. Two different groups are recognized, separated by a major unconformity. The Lower Group is dated at 2 to 3 Ma and includes the products of several volcanic centres, which together represent several cycles. The Upper Group ranges from 1.56 to 0.17 Ma and includes three different formations representing three long-term (∼ 100 to 300 Ka) volcanic cycles. The periods of dormancy between each formation were of ∼ 120 to 250 Ka duration. The Las Canadas caldera is a multicyclic caldera which formed over the period 1.18–0.17 Ma. Each cycle of activity represented by a formation culminated in caldera collapse which affected different sectors of the Las Canadas edifice. Geological observation and geochronology support an origin by collapse into a magma chamber. The minimum volume of pyroclastic ejecta is substantially greater than the present caldera depression volume (45 km3), but approaches the inferred volume of the original caldera depression (> 140 km3). After the formation of the caldera, sector collapses could also occur at the northern flank of the volcano causing the disappearance of the northern side of the caldera wall.

Intrusive history of the Slieve Gullion ring dyke, Ireland: implications for the internal structure of silicic sub-caldera magma chambers

2004 ◽  
Vol 68 (5) ◽  
pp. 725-738 ◽  
Author(s):  
S. McDonnell ◽  
V. R. Troll ◽  
C. H. Emeleus ◽  
I. G. Meighan ◽  
D. Brock ◽  
...  
Keyword(s):  
Granitic Magma ◽  
Caldera Collapse ◽  
Magma Chambers ◽  
Magma Body ◽  
Rock Types ◽  
Geochemical Variations ◽  
History Of ◽  
Complex Relationships ◽  
Chemical Groups ◽  
Ring Dyke

AbstractThe Palaeogene Slieve Gullion Igneous Complex comprises a layered central intrusion surrounded by a slightly older ring dyke. The ring dyke contains two major intrusive rock types. About 70% of the ring dyke is occupied by porphyritic granophyre and 30% by porphyritic felsite. Locally complex relationships between the two lithologies are observed. Major and trace element compositions suggest that there are two distinct chemical groups within each lithology: a Si-rich felsite, concentrated in a ~1 m wide zone at the outer margins of the dyke which grades into a less Si-rich felsite towards the interior. Similarly, a Si-rich granophyre, concentrated in the centre of the intrusion grades outwards into a Si-poor granophyre facies.These rock relationships and geochemical variations suggest that a complex magma chamber hosted a stratified granitic magma body and various wall/floor magma facies. Low density, high-Si felsite magma from the top of the chamber was tapped first, followed by less Si-rich felsite magma as evacuation proceeded. The granophyres probably originate from the chamber walls/floor, representing more mushy equivalents of the felsite magma. Little granophyre magma was tapped during the early stages of the evacuation sequence. As evacuation continued, probably aided by trap-door caldera collapse, the ‘granophyre magmas’ intruded the already emplaced and slightly cooled felsite, forming the complexly zoned structure of the Slieve Gullion ring intrusion.

Explosive volcanism on Santorini, Greece

1989 ◽  
Vol 126 (2) ◽  
pp. 95-126 ◽  
Author(s):  
T. H. Druitt ◽  
R. A. Mellors ◽  
D. M. Pyle ◽  
R. S. J. Sparks
Keyword(s):  
Explosive Volcanism ◽  
Volcanic Field ◽  
Pyroclastic Flows ◽  
Coarse Grained ◽  
Magma Ascent ◽  
Explosive Eruptions ◽  
Caldera Collapse ◽  
Caldera Wall ◽  
Magma Chambers ◽  
Facies Associations

AbstrctSantorini volcanic field has had 12 major (1–10 km3 or more of magma), and numerous minor, explosive eruptions over the last ~ 200 ka. Deposits from these eruptions (Thera Pyroclastic Formation) are well exposed in caldera-wall successions up to 200 m thick. Each of the major eruptions began with a pumice-fall phase, and most culminated with emplacement of pyroclastic flows. Pyroclastic flows of at least six eruptions deposited proximal lag deposits exposed widely in the caldera wall. The lag deposits include coarse-grained lithic breccias (andesitic to rhyodacitic eruptions) and spatter agglomerates (andesitic eruptions only). Facies associations between lithic breccia, spatter agglomerate, and ignimbrite from the same eruption can be very complex. For some eruptions, lag deposits provide the only evidence for pyroclastic flows, because most of the ignimbrite is buried on the lower flanks of Santorini or under the sea. At least eight eruptions tapped compositionally heterogeneous magma chambers, producing deposits with a range of zoning patterns and compositional gaps. Three eruptions display a silicic–silicic + mafic–silicic zoning not previously reported. Four eruptions vented large volumes of dacitic or rhyodacitic pumice, and may account for 90% or more of all silicic magma discharged from Santorini. The Thera Pyroclastic Formation and coeval lavas record two major mafic-to-silicic cycles of Santorini volcanism. Each cycle commenced with explosive eruptions of andesite or dacite, accompanied by construction of composite shields and stratocones, and culminated in a pair of major dacitic or rhyodacitic eruptions. Sequences of scoria and ash deposits occur between most of the twelve major members and record repeated stratocone or shield construction following a large explosive eruption.Volcanism at Santorini has focussed on a deep NE–SW basement fracture, which has acted as a pathway for magma ascent. At least four major explosive eruptions began at a vent complex on this fracture. Composite volcanoes constructed north of the fracture were dissected by at least three caldera-collapse events associated with the pyroclastic eruptions. Southern Santorini consists of pryoclastic ejecta draped over a pre-volcanic island and a ridge of early- to mid-Pleistocene volcanics. The southern half of the present-day caldera basin is a long-lived, essentially non-volcanic, depression, defined by topographic highs to the south and east, but deepened by subsidence associated with the main northern caldera complex, and is probably not a separate caldera.

Atypical Femoral Fracture in McCune-Albright Syndrome

2020 ◽  
Vol 7 (3) ◽  
pp. 147-152
Author(s):  
Salman Ghaffari ◽  
◽  
Mehran Razavipour ◽  
Parastoo Mohammad Amini ◽  
◽  
...  
Keyword(s):  
Femoral Fracture ◽  
Dynamic Compression ◽  
Plate Fixation ◽  
Medullary Canal ◽  
Mccune Albright Syndrome ◽  
Café Au Lait Spots ◽  
History Of ◽  
Albright Syndrome ◽  
Mccune Albright

McCune-Albright Syndrome (MAS) is characterized by endocrinopathies, café-au-lait spots, and fibrous dysplasia. Bisphosphonates are the most prescribed treatment for reducing the pain but their long-term use has been associated with atypical fractures of cortical bones like femur in patients. We present a 23-year-old girl diagnosed with MAS. She had an atypical mid-shaft left femoral fracture that happened during simple walking. She also had a history of long-term use of alendronate. Because of the narrow medullary canal, we used 14 holes hybrid locking plate for the lateral aspect of the thigh to fix the fracture and 5 holes dynamic compression plate (instead of the intramedullary nail) in the anterior surface to double fix it, reducing the probability of device failure. With double plate fixation and discontinuation of alendronate, the complete union was achieved five months after surgery

European Integration

2020 ◽  
Author(s):  
Johann P. Arnason
Keyword(s):  
European Integration ◽  
Eastern European ◽  
The European Union ◽  
Historical Processes ◽  
History Of ◽  
External Conditions ◽  
Eastern European Countries ◽  
Totalitarian Regimes ◽  
The Eu

Different understandings of European integration, its background and present problems are represented in this book, but they share an emphasis on historical processes, geopolitical dynamics and regional diversity. The introduction surveys approaches to the question of European continuities and discontinuities, before going on to an overview of chapters. The following three contributions deal with long-term perspectives, including the question of Europe as a civilisational entity, the civilisational crisis of the twentieth century, marked by wars and totalitarian regimes, and a comparison of the European Union with the Habsburg Empire, with particular emphasis on similar crisis symptoms. The next three chapters discuss various aspects and contexts of the present crisis. Reflections on the Brexit controversy throw light on a longer history of intra-Union rivalry, enduring disputes and changing external conditions. An analysis of efforts to strengthen the EU’s legal and constitutional framework, and of resistances to them, highlights the unfinished agenda of integration. A closer look at the much-disputed Islamic presence in Europe suggests that an interdependent radicalization of Islamism and the European extreme right is a major factor in current political developments. Three concluding chapters adopt specific regional perspectives. Central and Eastern European countries, especially Poland, are following a path that leads to conflicts with dominant orientations of the EU, but this also raises questions about Europe’s future. The record of Scandinavian policies in relation to Europe exemplifies more general problems faced by peripheral regions. Finally, growing dissonances and divergences within the EU may strengthen the case for Eurasian perspectives.

The natural history of pituitary apoplexy: long term follow-up study

2019 ◽  
Author(s):  
Ayesha Shaikh ◽  
Natasha Shrikrishnapalasuriyar ◽  
Giselle Sharaf ◽  
David Price ◽  
Maneesh Udiawar ◽  
...  
Keyword(s):  
Natural History ◽  
Pituitary Apoplexy ◽  
Follow Up Study ◽  
Long Term Follow Up ◽  
History Of

1386-P: Long-Term Weight Change after Pregnancy and Type 2 Diabetes Risk in Women with a History of Gestational Diabetes

Diabetes ◽  
2020 ◽  
Vol 69 (Supplement 1) ◽  
pp. 1386-P
Author(s):  
SYLVIA E. BADON ◽  
FEI XU ◽  
CHARLES QUESENBERRY ◽  
ASSIAMIRA FERRARA ◽  
MONIQUE M. HEDDERSON
Keyword(s):  
Type 2 Diabetes ◽  
Gestational Diabetes ◽  
Weight Change ◽  
Diabetes Risk ◽  
History Of

Update on the Boundaries of the Curly Birch Range

2020 ◽  
pp. 9-21
Author(s):  
L.V. Vetchinnikova ◽  
◽  
A.F. Titov ◽  
◽  
Keyword(s):  
Population Size ◽  
Natural Populations ◽  
Forest Tree ◽  
Published Data ◽  
Population Approach ◽  
Key Factors ◽  
History Of ◽  
Individual Trees ◽  
Karelian Birch

The article reports on the application of the best known principles for mapping natural populations of curly (Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti – one of the most appealing representatives of the forest tree flora. Relying on the synthesis and analysis of the published data amassed over nearly 100 years and the data from own full-scale studies done in the past few decades almost throughout the area where curly birch has grown naturally, it is concluded that its range outlined in the middle of the 20th century and since then hardly revised is outdated. The key factors and reasons necessitating its revision are specified. Herewith it is suggested that the range is delineated using the population approach, and the key element will be the critical population size below which the population is no longer viable in the long term. This approach implies that the boundaries of the taxon range depend on the boundaries of local populations (rather than the locations of individual trees or small clumps of trees), the size of which should not be lower than the critical value, which is supposed to be around 100–500 trees for curly birch. A schematic map of the curly birch range delineated using this approach is provided. We specially address the problem of determining the minimum population size to secure genetic diversity maintenance. The advantages of the population approach to delineating the distribution range of curly birch with regard to its biological features are highlighted. The authors argue that it enables a more accurate delineation of the range; shows the natural evolutionary history of the taxon (although it is not yet officially recognized as a species) and its range; can be relatively easily updated (e.g. depending on the scope of reintroduction); should be taken into account when working on the strategy of conservation and other actions designed to maintain and regenerate this unique representative of the forest tree flora.

Long Term Monitoring of the Macrobenthos of the Upper Clyde Estuary

1984 ◽  
Vol 16 (5-7) ◽  
pp. 359-373 ◽  
Author(s):  
Anne R Henderson
Keyword(s):  
Water Quality ◽  
Seasonal Variation ◽  
Organic Pollution ◽  
Long Term Changes ◽  
Pollution Loading ◽  
Faunal Density ◽  
History Of ◽  
Long Term Monitoring ◽  
Term Monitoring

The sublittoral macrobenthic invertebrate populations of the Upper Clyde Estuary are described. The estuary has a long history of organic pollution. The long term changes in species composition, faunal density and dominance patterns between 1974 and 1980 are presented. The fauna is dominated by brackish, pollution tolerant oligochaetes and polychaetes. Fluctuations in populations can be related to both seasonal variation in environmental conditions and long term improvements in water quality through a reduction in pollution loading to the estuary.

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