scholarly journals Effusive Monogenetic Volcanism

2020 ◽  
Author(s):  
Hugo Murcia ◽  
Károly Németh
Keyword(s):  
Classification Scheme ◽  
Wide Spectrum ◽  
Lava Flows ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Monogenetic Volcanism ◽  
Future Studies ◽  
Lava Domes ◽  
Tectonic Settings ◽  
Monogenetic Volcanoes

The study of monogenetic volcanism around Earth is rapidly growing due to the increasing recognition of monogenetic volcanic edifices in different tectonic settings. Far from the idea that this type of volcanism is both typically mafic and characteristic from intraplate environments, it occurs in a wide spectrum of composition and geological settings. This volcanism is widely known by the distinctive pyroclastic cones that represent both magmatic and phreatomagmatic explosive activity; they are known as scoria or spatter cones, tuff cones, tuff rings, maars and maar-diatremes. These cones are commonly associated with lava domes and usually accompanied by lava flows as part of their effusive eruptive phases. In spite of this, isolated effusive monogenetic emissions also appear around Earth’s surface. However, these isolated emissions are not habitually considered within the classification scheme of monogenetic volcanoes. Along with this, many of these effusive volcanoes also contrast with the belief that this volcanism is indicative of rapidly magma ascent from the asthenosphere, as many of the products are strongly evolved reflecting differentiation linked to stagnation during ascent. This has led to the understanding that the asthenosphere is not always the place that directly gives rise to the magma batches and rather, they detach from a crustal melt storage. This chapter introduces four singular effusive monogenetic volcanoes as part of the volcanic geoforms, highlights the fact that monogenetic volcanic fields can also be associated with crustal reservoirs, and outlines the processes that should occur to differentiate the magma before it is released as intermediate and acidic in composition. This chapter also provides an overview of this particular volcanism worldwide and contributes to the monogenetic comprehension for future studies.

scholarly journals Declassifying Myrmecophily in the Coleoptera to Promote the Study of Ant-Beetle Symbioses

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Glené Mynhardt
Keyword(s):  
Classification Scheme ◽  
Morphological Characteristics ◽  
Behavioral Data ◽  
Target Species ◽  
Classification Schemes ◽  
Future Studies ◽  
Symbiotic Associations ◽  
Behavioral Studies ◽  
Morphological Adaptations ◽  
Evolutionary Studies

The symbiotic associations between beetles and ants have been observed in at least 35 beetle families. Among myrmecophiles, beetles exhibit the most diverse behavioral and morphological adaptations to a life with ants. These various associations have historically been grouped into discrete but overlapping behavioral categories, many of which are still used in the modern literature. While these behavioral classifications provide a rich foundation for the study of ant-beetle symbioses, the application of these systems in future studies may be less than effective. Since morphological characteristics often provide the only information of myrmecophilous beetles, they should be studied in a species-by-species fashion, as behavioral data are often limited or unavailable. Similarly, behavioral studies should focus on the target species at hand, avoiding discrete classification schemes. I formally propose the rejection of any classification scheme, in order to promote future studies of myrmecophily in both taxonomic and evolutionary studies.

Shaping the nebulous enhancer in the era of high-throughput assays and genome editing

2019 ◽  
Vol 21 (3) ◽  
pp. 836-850
Author(s):  
Edwin Yu-Kiu Ho ◽  
Qin Cao ◽  
Mengting Gu ◽  
Ricky Wai-Lun Chan ◽  
Qiong Wu ◽  
...  
Keyword(s):  
Genome Editing ◽  
High Throughput ◽  
Wide Spectrum ◽  
Data Interpretation ◽  
Future Studies ◽  
Transcriptional Enhancers ◽  
The Past ◽  
Genome Wide ◽  
Gray Areas ◽  
Practical Implications

Abstract Since the 1st discovery of transcriptional enhancers in 1981, their textbook definition has remained largely unchanged in the past 37 years. With the emergence of high-throughput assays and genome editing, which are switching the paradigm from bottom-up discovery and testing of individual enhancers to top-down profiling of enhancer activities genome-wide, it has become increasingly evidenced that this classical definition has left substantial gray areas in different aspects. Here we survey a representative set of recent research articles and report the definitions of enhancers they have adopted. The results reveal that a wide spectrum of definitions is used usually without the definition stated explicitly, which could lead to difficulties in data interpretation and downstream analyses. Based on these findings, we discuss the practical implications and suggestions for future studies.

Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1216-1220
Author(s):  
Drew T. Downs ◽  
Duane E. Champion ◽  
Patrick Muffler ◽  
Robert L. Christiansen ◽  
Michael A. Clynne ◽  
...  
Keyword(s):  
Magma Ascent ◽  
Middle Pleistocene ◽  
Normal Faults ◽  
Northern California ◽  
Spatially Distributed ◽  
Dry Lake ◽  
Eruption Age ◽  
Tectonic Settings ◽  
Back Arc ◽  
Crustal Magma

Abstract Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the Tennant, Dry Lake, and Hammond Crossing basalt fields. Paleomagnetic analysis of these chemically similar basalts yield notable overlap, with statistical analysis yielding 7 chances in 1,000,000 that their similar mean remanent directions are random. These basalts also have overlapping 40Ar/39Ar ages of 272.5 ± 30.6 ka (Tennant), 305.8 ± 23.9 ka (Dry Lake), and 300.4 ± 15.2 and 322.6 ± 17.4 ka (Hammond Crossing). Chemical and paleomagnetic analyses indicate that these spatially distributed basalts represent simultaneous (<100 yr uncertainty) eruptions, and thus we use 305.5 ± 9.8 ka (weighted mean) as the eruption age. Their vents align on a N25°W trend over a distance of 39 km. Tennant erupted the largest volume (3.55 ± 0.75 km3) at the highest elevation; both factors decay to the south-southeast at Dry Lake (0.75 ± 0.15 km3) and Hammond Crossing (0.15 ± 0.05 km3). We propose vertical magma ascent beneath the Tennant vent area, where the most evolved, high-SiO2 magma erupted, with lateral dike propagation in the brittle crust. Propagation was near orthogonal to east-west extension (0.3–0.6 mm/yr) along north-northwest–trending normal faults.

scholarly journals Everyday Pain in Three- to Five-Year-Old Children in Day Care

1998 ◽  
Vol 3 (2) ◽  
pp. 111-116 ◽  
Author(s):  
Carl L von Baeyer ◽  
Shannon Baskerville ◽  
Patrick J McGrath
Keyword(s):  
Day Care ◽  
Classification Scheme ◽  
Body Part ◽  
First Aid ◽  
Pain Scale ◽  
Care Staff ◽  
Future Studies ◽  
Day Care Centres ◽  
Median Rate

A new event sampling instrument, the Dalhousie Everyday Pain Scale, was used to observe 50 children in six day care centres in Saskatoon for an average of 2.24 h each. The nature of minor painful incidents (eg, collisions and falls) was recorded, including distress behaviours and responses from peers and adults. Twenty-nine children (58%) were observed to experience one or more painful incidents, producing a total of 51 incidents and yielding a median rate of incidents of 0.31 per child per hour, a rate similar to that reported in another Canadian sample. Seven of nine child response items met criteria for reliability in a subsample of incidents observed simultaneously by two observers. Rubbing the affected body part, crying and making verbal statements about the injury were the most common responses to painful incidents. Intervention by day care staff was strongly associated with children's facial expression of distress: physical and first aid interventions were offered most frequently to children who displayed the greatest facial distress. Content analysis of observers' records produced a classification scheme for causes of painful incidents. Twenty per cent of painful incidents were judged to be the result of deliberate actions by other children. The classification of causes may be a useful addition to the scale for application in future studies of everyday pain and injury prevention.

scholarly journals Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

Solid Earth ◽  
2010 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
D. Giordano ◽  
M. Polacci ◽  
P. Papale ◽  
L. Caricchi
Keyword(s):  
Solid Particles ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Summit Eruption ◽  
Intermediate Phases ◽  
Strombolian Eruption ◽  
Mt Etna ◽  
Order Of Magnitude ◽  
Crystal Content ◽  
Fire Fountain

Abstract. In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterized by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East Crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content (>55 vol%) with respect to the magma discharged during the fire-fountain phases (~35 vol%). Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modeling of steady magma ascent dynamics (as assumed for the fire-fountain activity), a large crystal content as the one found for products of Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. We argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged favoured conditions corresponding to Strombolian activity, with fire-fountain activity resuming after removal of the highly crystalline top. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

scholarly journals Rheological change and degassing during a trachytic Vulcanian eruption at Kilian Volcano, Chaîne des Puys, France

2020 ◽  
Vol 82 (12) ◽  
Author(s):  
Mathieu Colombier ◽  
Thomas Shea ◽  
Alain Burgisser ◽  
Timothy H. Druitt ◽  
Lucia Gurioli ◽  
...  
Keyword(s):  
Water Solubility ◽  
Pore Space ◽  
High Water ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Pore Collapse ◽  
Melt Viscosity ◽  
Effusive Activity ◽  
Volatile Loss ◽  
Magma Viscosity

AbstractMagma ascent during silicic dome-forming eruptions is characterized by significant changes in magma viscosity, permeability, and gas overpressure in the conduit. These changes depend on a set of parameters such as ascent rate, outgassing and crystallization efficiency, and magma viscosity, which in turn may influence the prevailing conditions for effusive versus explosive activity. Here, we combine chemical and textural analyses of tephra with viscosity models to provide a better understanding of the effusive-explosive transitions during Vulcanian phases of the 9.4 ka eruption of Kilian Volcano, Chaîne des Puys, France. Our results suggest that effusive activity at the onset of Vulcanian episodes at Kilian Volcano was promoted by (i) rapid ascent of initially crystal-poor and volatile-rich trachytic magma, (ii) a substantial bulk and melt viscosity increase driven by extensive volatile loss and crystallization, and (iii) efficient degassing/outgassing in a crystal-rich magma at shallow depths. Trachytic magma repeatedly replenished the upper conduit, and variations in the amount of decompression and cooling caused vertical textural stratification, leading to variable degrees of crystallization and outgassing. Outgassing promoted effusive dome growth and occurred via gas percolation through large interconnected vesicles, fractures, and tuffisite veins, fostering the formation of cristobalite in the carapace and talus regions. Build-up of overpressure was likely caused by closing of pore space (bubbles and fractures) in the dome through a combination of pore collapse, cristobalite formation, sintering in tuffisite veins, and limited pre-fragmentation coalescence in the dome or underlying hot vesicular magma. Sealing of the carapace may have caused a transition from open- to closed- system degassing and to renewed explosive activity. We generalize our findings to propose that the broad spectrum of eruptive styles for trachytic magmas may be inherited from a combination of characteristics of trachytic melts that include high water solubility and diffusivity, rapid microlite growth, and low melt viscosity compared to their more evolved subalkaline dacitic and rhyolitic equivalents. We show that trachytes may erupt with a similar style (e.g., Vulcanian) but at significantly higher ascent rates than their andesitic, dacitic, and rhyolitic counterparts. This suggests that the periodicity of effusive-explosive transitions at trachytic volcanoes may differ from that observed at the well-monitored andesitic, dacitic, and rhyolitic volcanoes, which has implications for hazard assessment associated with trachytic eruptions.

Vesicle paleobarometry in the Pongola Supergroup: A cautionary note and guidelines for future studies

2020 ◽  
Vol 123 (1) ◽  
pp. 95-104
Author(s):  
E.A. Goosmann ◽  
R. Buick ◽  
D.C. Catling ◽  
C. Luskin ◽  
N. Nhleko
Keyword(s):  
Sea Level ◽  
Barometric Pressure ◽  
Air Pressure ◽  
Gas Absorption ◽  
Lava Flows ◽  
Pressure Broadening ◽  
Basalt Lava ◽  
Future Studies ◽  
Kwazulu Natal ◽  
X Ray Computed

Abstract Earth’s global barometric pressure, currently 1 bar at sea level, may have changed over its 4.5-billion-year history. Proxy measurements, including N2/36Ar ratios in ~3.5 to 3.0 Ga hydrothermal quartz, ~2.7 Ga raindrop imprints, and ~2.7 Ga vesicle sizes in subaerial basalt lava flows indicate Archean air pressure could have been between 0.1 and 1.2 bar. However, some models argue air pressure in the Archean should have been much higher than now and could allow pressure broadening of greenhouse gas absorption lines to counteract the “Faint Young Sun”. Thus, additional paleobarometric measurements would be useful to further constrain Earth’s atmospheric evolution. We attempted to use vesicle sizes in lavas erupted near sea-level from the ~2.9 Ga Pongola Supergroup from Mahlangatsha and Mooihoek, eSwatini (formerly Swaziland) and the White Mfolozi River gorge of KwaZulu-Natal, South Africa to provide further Archean paleobarometric data. However, reliable results were unobtainable due to small and scarce amygdales, irregular vesicle morphologies and metamorphic mineralogical homogenization preventing the use of X-ray Computed Tomography for accurate vesicle size determination. Researchers attempting paleobarometric analysis using lava vesicle sizes should henceforth avoid these areas of the Pongola Supergroup and instead look at other subaerially emplaced lava flows. With this being only the second time this method has been used on Precambrian rocks, we provide a list of guidelines informed by this study to aid future attempts at vesicular paleobarometry.

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