scholarly journals Eruption Sequences and Characteristics of Weizhou Island Volcano, Guangxi Province, South of China

2021 ◽  
Vol 9 ◽  
Author(s):  
Hongmei Yu ◽  
Wenjian Yang ◽  
Bo Zhao ◽  
Zhengquan Chen ◽  
Bin Zhou ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Explosive Eruption ◽  
Early Pleistocene ◽  
Explosive Eruptions ◽  
Composition Analysis ◽  
Second Phase ◽  
Density Currents ◽  
Rock Composition ◽  
The North ◽  
Effusive Eruptions

Weizhou island, located in the north margin of the South China Sea (SCS), is characterized by multi-stage volcanism, several eruption styles and eruption craters, and is also the youngest Quaternary volcanic island in China. An eruption on this island may pose high risk to life and property. However, the eruptive history of Weizhou island, the craters number and location, and their eruptive sequence and characteristics are still being debated, which are important for potential volcanic hazard assessment. In the present study, field surveys, 40Ar/39Ar and 14C geochronological studies and whole rock composition analysis of volcanic rock are used to investigate the eruption sequences associated with Weizhou island and the characteristics of each period. Four volcanoes were discovered at Henglushan, Hengling, Nanwan and Daling. The Henglushan and Hengling volcanoes were produced by early weak explosive and late effusive eruptions, and lavas from these volcanoes represent the foundation of island. Conversely, the Nanwan and Daling volcanoes are linked to multiple explosive eruption phases, with hydromagmatic eruptions in the first and last phase and a magmatic explosive eruption in the second phase. The pyroclastic density currents (PDCs) deposits of the Nanwan and Daling volcanoes virtually cover the entire island. Volcanic activity in Weizhou island started in Early Pleistocene and ended in Late Pleistocene. This can be divided into the following distinct periods: 1,420–1,260, 870–740, 600–480, 283–222 ka, and 33.7–13 ka. The first four periods were dominated by effusive eruptions associated with the Henglushan and Hengling volcanoes, which peaked between 870 and 740 ka. After this period, explosive eruptions began at around 33.7 ka because of magma–water interactions. These explosive eruptions then created the Nanwan and Daling volcanoes. Early effusive lava flows in Weizhou island are characterized by basaltic compositions and are linked with a small amount of fractional crystallization. Magmas in later eruptions contained slightly lower SiO2 and involved some basanite. Fractional crystallization was also less pronounced in these lavas because of their rapid ascent.

scholarly journals The 2020 Activity of Kamchatkan Volcanoes and Danger to Aviation

2021 ◽  
Author(s):  
Olga Girina ◽  
Melnikov Dmitry ◽  
Manevich Alexander ◽  
Nuzhdaev Anton ◽  
Romanova Iraida ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Explosive Eruption ◽  
Lava Dome ◽  
Explosive Eruptions ◽  
Jet Engines ◽  
Eruptive Activity ◽  
Long Time ◽  
Karymsky Volcano ◽  
June July ◽  
Effusive Eruptions

<p>Strong explosive eruptions of volcanoes are the most dangerous for aircraft because they can produce in a few hours or days to the atmosphere and the stratosphere till several cubic kilometers of volcanic ash and aerosols. Ash plumes and the clouds, depending on the power of the eruption, the strength and wind speed, can travel thousands of kilometers from the volcano for several days, remaining hazardous to aircraft, as the melting temperature of small particles of ash below the operating temperature of jet engines.</p><p>There are 30 active volcanoes in the Kamchatka, and several of them are continuously active. Scientists of KVERT monitor Kamchatkan volcanoes since 1993. In 2020, four of these volcanoes (Sheveluch, Klyuchevskoy, Bezymianny, and Karymsky) had strong and moderate explosive eruptions.</p><p>The eruptive activity of Sheveluch volcano began since 1980 (growth of the lava dome) and it is continuing at present. In 2020, strong explosions sent ash up to 7-10 km a.s.l. on 08 April, and 22 and 29 December. Ash from explosions rose up to 5-6 km a.s.l. on 13 June, and 24 December. Ash plumes extended more 625 km mainly to the south-east of the volcano. A form of resuspended ash was observed on 20 April, 28 June, 24 August, and 07-10 October: ash plumes extended for 310 km to the northeast and southeast of the volcano. Activity of Sheveluch was dangerous to international and local aviation.</p><p>Two moderate explosive-effusive eruptions of Klyuchevskoy volcano occurred in 2020: first from 01 November 2019 till 03 July 2020, and second from 30 September, it is continuing in 2021. Explosions sent ash up to 7 km a.s.l., gas-steam plumes containing some amount of ash extended for 465 km to the different directions of the volcano. The lava flows moved along Apakhonchichsky and Kozyrevsky chutes. Activity of the volcano was dangerous to local aviation.</p><p>The strong explosive eruption of Bezymianny volcano occurred on 21 October: explosions sent ash up to 11 km a.s.l., the large ash cloud was located over Klyuchevskoy group of volcanoes long time and later drifted up to1200 km to the southeast of the volcano. Activity of the volcano was dangerous to international and local aviation.</p><p>Eruptive activity of Karymsky volcano was uneven in 2020: ash explosions were observed from one (June) to seven (October) days a month, for five months the volcano was quiet. Explosions rose ash up to 8 km a.s.l. (08 November), ash plumes and clouds drifted for 380 km to the different directions of the volcano. The eruptive volcanic activity was observed in April, May, June, July, October, November, and December. Activity of Karymsky was dangerous to international and local aviation.</p>

Geographical restriction as a guide to the causes of extinction: the case of the cold northern oceans during the Neogene

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 335-356 ◽  
Author(s):  
Geerat J. Vermeij
Keyword(s):  
Primary Productivity ◽  
North Pacific ◽  
Early Pleistocene ◽  
Northwestern Pacific ◽  
Supporting Evidence ◽  
Geographical Patterns ◽  
The North ◽  
The Pacific ◽  
Late Neogene ◽  
The North Pacific

Geographical restriction to refuges implies the regional extinction of taxa in areas of the previous range falling outside the refuge. A comparison of the circumstances in the refuge with those in areas from which the taxa were eliminated is potentially informative for pinpointing the causes of extinction. A synthesis of data on the geographical and stratigraphical distributions of cool-water molluscs of the North Pacific and North Atlantic Oceans during the late Neogene reveals four patterns of geographical restriction, at least two of which imply that climatic cooling was not the only cause of extinction during the last several million years. These four patterns are (1) the northwestern Pacific restriction, involving 15 taxa whose amphi-Pacific distributions during the late Neogene became subsequently restricted to the Asian side of the Pacific; (2) the northwestern Atlantic restriction, involving six taxa whose early Pleistocene distribution is inferred to have been amphi-Atlantic, but whose present-day and late Pleistocene ranges are confined to the northwestern Atlantic; (3) a vicariant Pacific pattern, in which many ancestral amphi-Pacific taxa gave rise to separate eastern and western descendants; and (4) the circumboreal restriction, involving six taxa whose early Pleistocene distribution, encompassing both the Atlantic and Pacific Oceans, became subsequently limited to the North Pacific. Like the Pliocene extinctions in the Atlantic, previously studied by Stanley and others, the vicariant Pacific pattern is most reasonably interpreted as having resulted from regional extinction of northern populations in response to cooling. The northwestern Pacific and Atlantic restrictions, however, cannot be accounted for in this way. In contrast to the northeastern margins of the Pacific and Atlantic, the northwestern margins are today characterized by wide temperature fluctuations and by extensive development of shore ice in winter. Northeastern, rather than northwestern, restriction would be expected if cooling were the overriding cause of regional extinction. Among the other possible causes of extinction, only a decrease in primary productivity can account for the observed northwestern and circumboreal patterns of restriction. Geographical patterns of body size and the distribution of siliceous deposits provide supporting evidence that primary productivity declined after the Miocene in the northeastern Pacific, but remained high in the northwestern Pacific, and that productivity in the Pacific is generally higher than it is in the Atlantic. The patterns of geographical restriction in the northern oceans thus provide additional support to previous inferences that reductions in primary productivity have played a significant role in marine extinctions.

scholarly journals Types of river sources of the thin-grained aluminosilicaclastics for the Jurassic and lower cretaceous deposits of the West Siberian megabasin

2021 ◽  
Vol 63 (4) ◽  
pp. 52-61
Author(s):  
A. V. Maslov
Keyword(s):  
Lower Cretaceous ◽  
The Urals ◽  
River Systems ◽  
The West ◽  
Rock Composition ◽  
Fine Grained ◽  
The North ◽  
Catchment Areas ◽  
Cretaceous Deposits ◽  
West Siberian Basin

Background. The lithogeochemical features of fine-grained detrital rocks (mudstones, shales, and fine-grained siltstones) allow, with a certain degree of success, the main parameters of the formation of sedimentary sequences to be reconstructed. These parameters include (primarily in terms of their REE and Th systematics) the types of river systems supplying thin terrigenous suspension in the sedimentation area: the rivers of the 1st category – large rivers with a catchment area of more than 100,000 km2; 2nd category – rivers feeding on the products of erosion of sedimentary deposits; 3rd category – rivers draining mainly igneous and metamorphic rocks; and 4th category – rivers carrying erosion products of volcanic associations.Aim. To reveal, based on the analysis of interrelationships between such parameters as (La/Yb)N, Eu/Eu* and the Th content, the types of river systems that fed the Jurassic and Lower Cretaceous deposits of the Shaim oil and gas region (OGR) (Sherkalinsky, Tyumen, Abalak and Mulymya formations) and the region of the North Pokachevsky field of the Shirotnoe Priobye region (Sherkalinsky, Tyumen and Bazhenov formations, Lower Cretaceous deposits).Materials and methods. The ICP MS data for almost 100 samples of mudstones and fine-grained clayey siltstones were used to analyse the features of distribution of lanthanides and Th in the Jurassic and Lower Cretaceous clayey rocks of the Shaim OGR and the area of the North Pokachevsky deposits. Individual and average composition points for formations, members and layers were plotted on the (La/Yb)N-Eu/Eu*, (La/Yb)N–Th diagrams developed by us with classification areas of the composition of fine suspended material of modern rivers of different categories.Results and conclusion. The results presented in the article showed that during the formation of the deposits of the Shaim OGR in the Early and Middle Jurassic, erosion affected either mainly sedimentary formations or paleo-catchment areas that were very variegated in their rock composition. In the Late Jurassic, the source area was, most likely, a volcanic province, composed mainly of igneous rocks of the basic composition, and located within the Urals. This conclusion suggested that the transfer of clastic material from the Urals to the Urals part of the West Siberian basin “revived” much earlier than the Hauterivian. The Jurassic-Lower Cretaceous section of the vicinity of the North Pokachevsky field was almost entirely composed of thin aluminosilicaclastics formed due to the erosion of volcanic formations. These volcanic formations were located, as followed from the materials of earlier performed paleogeographic reconstructions, probably within the Altai-Sayan region or Northern Kazakhstan. Thus, the supply of detrital material in the considered territories of the West Siberian basin had a number of significant differences in the Jurassic and early Cretaceous.

scholarly journals THE LOWER SILURIAN TERRIGENOUS DEPOSITS OF THE LAOELING-GRODEKOVO TERRANE (SOUTH PRIMORYE): MATERIAL COMPOSITION AND FORMATION SETTINGS

2021 ◽  
pp. 25-44
Author(s):  
A.I. Malinovsky ◽  
◽  
V.V. Golozubov ◽  
Keyword(s):  
Sedimentary Basin ◽  
Volcanic Rocks ◽  
Source Area ◽  
Island Arc ◽  
Material Composition ◽  
Recycling Rate ◽  
Composition Analysis ◽  
Rock Composition ◽  
South Primorye ◽  
Genetic Interpretation

This paper studies the original results of the material composition analysis of the Early Silurian terrigenous deposits of the Kordonka formation of the Paleozoic – Early Mesozoic Laoeling-Grodekovo terrane of the South Primorye. The research is aimed at reconstructing paleogeodynamic setting of the deposition of sediments of the formation, and determining the type and mother rock composition of the feed sources based on the complex genetic interpretation of the material composition of rocks. It was established that mineralogically and geochemically formation of the rocks correspond to the typical graywackes and represent petrogenic or “first cycle” rocks formed mainly through the source rock failure. They are characterized by a low maturity, low lithodynamic recycling rate of mother rocks and their rapid burial. The interpretation of the results of the complex study of the material composition of the rocks was carried out on the basis of its comparison with the compositions of ancient rocks and modern sediments formed in the well-known geodynamic settings. The obtained data indicate that deposits of the Kordonka formation accumulated in a sedimentary basin connected with an oceanic island arc. Being built by basic and intermediate volcanic rocks as well as by igneous and sedimentary rocks that constituted its base, this island arc was the source area that supplied clastic material to the aforementioned sedimentary basin.

scholarly journals Assessing the impact of explosive eruptions of Fogo volcano (São Miguel, Azores) on the tourism economy

2021 ◽  
Vol 21 (1) ◽  
pp. 417-437
Author(s):  
Joana Medeiros ◽  
Rita Carmo ◽  
Adriano Pimentel ◽  
José Cabral Vieira ◽  
Gabriela Queiroz
Keyword(s):  
Economic Impact ◽  
Economic Loss ◽  
Volcanic Hazards ◽  
Plinian Eruption ◽  
Explosive Eruptions ◽  
Density Currents ◽  
Economic Sectors ◽  
Worst Case ◽  
The Impact ◽  
Fogo Volcano

Abstract. The Azores are an active volcanic region that offers exceptional conditions for nature-based tourism, one of the main axes of economic growth in the archipelago. A future volcanic eruption may have long-term consequences to this economic sector. Therefore, it is fundamental to assess its vulnerability to volcanic hazards in order to try to mitigate the associated risk. This study proposes a new approach to assessing the economic impact of explosive eruptions on the tourism sector. We considered two eruptive scenarios for Fogo volcano (São Miguel Island), the most probable (Volcanic Explosivity Index, VEI, 4 sub-Plinian eruption) and the worst-case (VEI 5 Plinian eruption), both producing tephra fallout and pyroclastic density currents. The results of numerical simulations were overlaid with tourism-related buildings and infrastructure of Vila Franca do Campo municipality to identify the elements at risk. The loss present value method was used to estimate the benefits generated by the accommodation units over 30 years for different economic scenarios. The assessment of the economic impact using 2018 indicators reveals that in a near-total-destruction scenario, the economic loss is approximately EUR 145 million (considering a 2 % discount rate). This approach can also be applied to other volcanic regions, geologic hazards and economic sectors.

Harvest of Briars

2019 ◽  
pp. 121-158
Author(s):  
A. Wess Mitchell
Keyword(s):  
Eighteenth Century ◽  
Ottoman Empire ◽  
Cost Effective ◽  
Balkan Peninsula ◽  
The Black Sea ◽  
Second Phase ◽  
Habsburg Monarchy ◽  
The West ◽  
The North ◽  
Third Phase

This chapter examines the competition with the Ottoman Empire and Russia, from the reconquest of Hungary to Joseph II’s final Turkish war. On its southern and eastern frontiers, the Habsburg Monarchy contended with two large land empires: a decaying Ottoman Empire, and a rising Russia determined to extend its influence on the Black Sea littorals and Balkan Peninsula. In balancing these forces, Austria faced two interrelated dangers: the possibility of Russia filling Ottoman power vacuums that Austria itself could not fill, and the potential for crises here, if improperly managed, to fetter Austria’s options for handling graver threats in the west. In dealing with these challenges, Austria deployed a range of tools over the course of the eighteenth century. In the first phase (1690s–1730s), it deployed mobile field armies to alleviate Turkish pressure on the Habsburg heartland before the arrival of significant Russian influence. In the second phase (1740s–70s), Austria used appeasement and militarized borders to ensure quiet in the south while focusing on the life-or-death struggles with Frederick the Great. In the third phase (1770s–90s), it used alliances of restraint to check and keep pace with Russian expansion, and recruit its help in comanaging problems to the north. Together, these techniques provided for a slow but largely effective recessional, in which the House of Austria used cost-effective methods to manage Turkish decline and avoid collisions that would have complicated its more important western struggles.

Notes on Fossil Chitons. 1. A new species of Lepidopleurus (Mollusca: Polyplacophora) from the Pleistocene of Salice (Sicily, Italy)

Zootaxa ◽  
2005 ◽  
Vol 821 (1) ◽  
pp. 1 ◽  
Author(s):  
BRUNO DELL’ANGELO ◽  
ANTONIO BONFITTO
Keyword(s):  
New Species ◽  
North Atlantic ◽  
Early Pleistocene ◽  
The North ◽  
The North Atlantic ◽  
A New Species

A new species of Polyplacophora (Mollusca) has been found in the Salice outcrop, in the Peloritain Mountains (Sicily, Italy), is attributed to the early Pleistocene. Lepidopleurus (Leptochiton) salicensis n.sp. is characterized by its uniformly sculptured tegmentum, with (well) raised, randomly distributed, neatly separated rounded/polygonal granules. The new species is compared with Lepidopleurus (Leptochiton) alveolus (M.Sars MS, Lovén, 1846), from the North Atlantic, and Lepidopleurus (Leptochiton) tavianii Dell’Angelo, Landau & Marquet, 2004, from the Pliocene of Estepona (Málaga, Spain).

scholarly journals Identification of an Al–Ni–O precipitate in combustion-synthesized NiAl

2000 ◽  
Vol 33 (5) ◽  
pp. 1217-1222
Author(s):  
A. Biswas ◽  
Madangopal K. ◽  
J. B. Singh ◽  
S. K. Roy ◽  
S. Banerjee
Keyword(s):  
Room Temperature ◽  
Point Group ◽  
Composition Analysis ◽  
Second Phase ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Phase Precipitate ◽  
Transmission Electron ◽  
Chemical Composition Analysis

The complete identity of a second-phase precipitate detected by transmission electron microscopy in combustion-synthesized NiAl was established. The crystal structure, including the point group, the space group and the lattice parameters, was determined by convergent and selected-area electron diffraction techniques. Energy dispersive X-ray spectroscopy was used for the determination of the chemical composition. Analysis established the phase to be the solid solution of NiO in Al2O3and presented evidence of the hitherto unreported room-temperature solubility.

scholarly journals Pompeian hiatuses: new stratigraphic data highlight pauses in the course of the ad 79 eruption at Pompeii

2020 ◽  
Vol 157 (4) ◽  
pp. 695-700
Author(s):  
Claudio Scarpati ◽  
Annamaria Perrotta ◽  
Alberta Martellone ◽  
Massimo Osanna
Keyword(s):  
Second Phase ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Pyroclastic Deposits ◽  
The Town

AbstractA new stratigraphic survey of the pyroclastic deposits blanketing Pompeii ruins shows departures from prior reconstruction of the events that occurred inside the town during the two main phases (pumice fallout and pyroclastic density currents) of the ad 79 Vesuvius eruption. We document the depth and distribution of subaerial erosion surfaces in the upper part of the pyroclastic sequence, formed during two short-lived breaks occurring in the course of the second phase of the eruption. These pauses could explain why 50% of the victims were found in the streets during the pyroclastic density currents phase.

Clyde Sea hydrography

1986 ◽  
Vol 90 ◽  
pp. 67-83 ◽  
Author(s):  
A. Edwards ◽  
M. S. Baxter ◽  
D. J. Ellett ◽  
J. H. A. Martin ◽  
D. T. Meldrum ◽  
...  
Keyword(s):  
Bottom Water ◽  
Surface Currents ◽  
Density Currents ◽  
Surface Layers ◽  
The North ◽  
Minor Part ◽  
A Minor ◽  
Clyde Sea ◽  
Mixed Water ◽  
Coarse To Fine

SynopsisA front on the Great Plateau separates tidally mixed water of the North Channel from quieter less saline surface layers of the Outer Firth. These water bodies exchange about 1·6 × 104m3 s−1, leading to a residence time of two months in the Outer Firth surface layers. The position of the front is determined by the balance of mixing and buoyancy supply. The wind modulates weak tidal currents in the Outer Firth by driving surface currents and setting up deeper compensation flows. Deep water in the Arran Deep and Kilbrannan Sound is irregularly renewed by inflow of dense water over the Eastern Plateau from autumn to spring of about 1 × 104m3 s−1 but stagnates in summer below a thermocline. A minor part of this renewal comes over the Davaar sill into Kilbrannan Sound.Bottom water of the fjordic sea-lochs is isolated in summer and renewed during the winter. The renewals occur by density currents flowing in from the sills and these produce a characterising grading of the bottom sediments from coarse to fine away from the sills.

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