1,807 results
Search Results
2. The South Turkana Expedition Scientific Papers I. Preliminary Report on the 1968 Season
- Author
-
Gwynne, M. D.
- Published
- 1969
- Full Text
- View/download PDF
3. The South Turkana Expedition: Scientific Papers III. A Geological Reconnaissance of South Turkana
- Author
-
Rhemtulla, Sultan
- Published
- 1970
- Full Text
- View/download PDF
4. The South Turkana Expedition: Scientific Papers IV: Land Units of the Lokori Area
- Author
-
Morgan, W. T. W.
- Published
- 1971
- Full Text
- View/download PDF
5. Abstracts: Papers Read at the Washington Meeting of the Geological Society of America
- Published
- 1897
6. Scientific papers and discussions at the 1925 meeting of the Section of Volcanology, American Geophysical Union
- Author
-
Sosman, Robert B.
- Published
- 1925
7. Scientific papers at the 1928 meeting of the Section of Volcanology, American Geophysical Union
- Published
- 1928
8. Still Life with Paper Wasp Nest and Lava Flow, and: Adansonia digitata (Baobab)
- Author
-
Sandra Meek
- Subjects
Paper wasp ,Geography ,Nest ,biology ,Ecology ,Lava ,Botany ,General Medicine ,Adansonia digitata ,biology.organism_classification - Published
- 2013
9. The Technical Papers of the National Geographic Society
- Published
- 1923
10. 3rd High-Lift Workshop Summary Paper - OpenFOAM, STAR-CCM+ & LAVA simulations on Unstructured Grids
- Author
-
Marie Denison, Neil Ashton, and Marian Zastawny
- Subjects
020301 aerospace & aeronautics ,0203 mechanical engineering ,business.industry ,Computer science ,Lava ,0103 physical sciences ,Star ccm ,02 engineering and technology ,Aerospace engineering ,business ,01 natural sciences ,High lift ,010305 fluids & plasmas - Published
- 2018
11. Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 1. Mode of emplacement in three areas1This article is a companion paper to Ross et al. 2011. Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology. Canadian Journal of Earth Sciences, 48: this issue.2MRNF Contribution BEGQ 8439-2010/2011-1. Natural Resources Canada, Earth Science Sector Contribution 20100253
- Author
-
Pierre-Simon Ross, Jean Goutier, Benoît Dubé, and Patrick Mercier-Langevin
- Subjects
Volcanic rock ,Basalt ,geography ,Submarine eruption ,geography.geographical_feature_category ,Felsic ,Lava ,Geochemistry ,General Earth and Planetary Sciences ,Pyroclastic rock ,Greenstone belt ,Mafic ,Geology - Abstract
The Archean Blake River Group (BRG) of Ontario and Quebec is dominated by submarine mafic to intermediate lavas, with more restricted felsic volcanic rocks. Given the good quality of outcrop, and high level of preservation of some BRG rocks, the mafic to intermediate lavas were used in the 1970s and 1980s to better understand the evolution of massive and pillowed submarine flows, and their associated fragmental facies (pillow breccias, hyaloclastite). Potentially, the BRG could also represent a useful volcanic succession for the study of explosive submarine eruption products in the ancient record. Before this is possible, however, a regional inventory of the mafic to intermediate volcaniclastic units is needed in order to clarify their characteristics and origins. In this paper, we compare and contrast volcaniclastic rocks from three areas within the same formation of the northern BRG in Quebec: the Monsabrais area, the lac Duparquet area, and the D’Alembert tuff area. Close examination reveals pronounced differences in terms of lateral continuity, thickness, grading, bedding, clast shapes, textures, etc. in the volcaniclastic rocks. These differences are interpreted to reflect vastly different emplacement processes ranging from hyaloclastite generation as a result of self-fragmentation and lava contact with water (dominant in the Monsabrais and lac Duparquet areas) to aqueous density currents likely fed directly by explosive submarine eruptions (dominant in the D’Alembert tuff).
- Published
- 2011
12. Oxygen isotope heterogeneity of the mantle beneath the Canary Islands: a discussion of the paper of Gurenko et al
- Author
-
David Lowry, Colin G. Macpherson, D. Graham Pearson, and James M.D. Day
- Subjects
Basalt ,Peridotite ,Olivine ,Lava ,Geochemistry ,Mineralogy ,Ocean island basalt ,engineering.material ,Silicate ,Mantle (geology) ,Isotopes of oxygen ,chemistry.chemical_compound ,Geophysics ,chemistry ,Geochemistry and Petrology ,engineering ,Geology - Abstract
Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) report laser-assisted fluorination (LF) and secondary ionization mass spectrometry (SIMS) 18O/16O datasets for olivine grains from the Canary Islands of Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro. As with prior studies of oxygen isotopes in Canary Island lavas (e.g. Thirlwall et al. Chem Geol 135:233–262, 1997; Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010), these authors find variations in δ18Ool (~4.6–6.0 ‰) beyond that measured for mantle peridotite olivine (Mattey et al. Earth Planet Sci Lett 128:231–241, 1994) and interpret this variation to reflect contributions from pyroxenite-peridotite mantle sources. Furthermore, Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) speculate that δ18Ool values for La Palma olivine grains measured by LF (Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) may be biased to low values due to the presence of altered silicate, possibly serpentine. The range in δ18Ool values for Canary Island lavas are of importance for constraining their origin. Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) took a subset (39 SIMS analyses from 13 grains from a single El Hierro lava; EH4) of a more extensive dataset (321 SIMS analyses from 110 grains from 16 Canary Island lavas) to suggest that δ18Ool is weakly correlated (R 2 = 0.291) with the parameter used by Gurenko et al. (Earth Planet Sci Lett 277:514–524, 2009) to describe the estimated weight fraction of pyroxenite-derived melt (Xpx). With this relationship, end-member δ18O values for HIMU-peridotite (δ18O = 5.3 ± 0.3 ‰) and depleted pyroxenite (δ18O = 5.9 ± 0.3 ‰) were defined. Although the model proposed by Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) implicates similar pyroxenite-peridotite mantle sources to those proposed by Day et al. (Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) and Day and Hilton (Earth Planet Sci Lett 305:226–234, 2011), there are significant differences in the predicted δ18O values of end member components in the two models. In particular, Day et al. (Geochim Cosmochim Acta 74:6565–6589, 2010) proposed a mantle source for La Palma lavas with low-δ18O (
- Published
- 2012
13. Reply to comment on paper: ‘Morphology and composition of spinel in Pu′u ′O′o lava (1996–1998), Kilauea volcano, Hawaii’—enigmatic discrepancies between lava and gas-based fO2 determinations of Pu′u ′O′o lava
- Author
-
A. Grant, Carl R. Thornber, and Peter L. Roeder
- Subjects
geography ,Geophysics ,geography.geographical_feature_category ,Morphology (linguistics) ,Volcano ,Geochemistry and Petrology ,Lava ,Spinel ,Geochemistry ,engineering ,Mineralogy ,engineering.material ,Geology - Published
- 2004
14. Comment on paper: ‘Morphology and compositions of spinel in Pu′u ′Ō′ō lava (1996–1998), Kilauea volcano, Hawaii′—enigmatic discrepancies between lava and gas-based fO2 determinations of Pu′u ′Ō′ō lava
- Author
-
Terrence M. Gerlach
- Subjects
geography ,Geophysics ,Morphology (linguistics) ,geography.geographical_feature_category ,Volcano ,Geochemistry and Petrology ,Lava ,Spinel ,engineering ,Mineralogy ,Fugacity ,engineering.material ,Geology - Published
- 2004
15. Comment on the Paper: 'Thermal survey of Mount Etna Volcano from space' by A. Bonneville and P. Gouze
- Author
-
C. Archambault and J. C. Tanguy
- Subjects
geography ,Geophysics ,geography.geographical_feature_category ,Etna volcano ,Volcano ,Lava ,Thermal ,General Earth and Planetary Sciences ,Space (mathematics) ,Mount ,Geology - Published
- 1993
16. Papers on corona
- Author
-
null Ryan, null Henline, null Clark, null Miller, null Carroll, null Peterson, null Stray, null Evanson, and null Wilkins
- Subjects
Volcanic rock ,geography ,geography.geographical_feature_category ,Field (physics) ,Lava ,Critical voltage ,Geophysics ,Corona ,Geology - Abstract
F. W. Peek, Jr.: It is my opinion that apparent discrepancies in the corona papers presented are not due to error in the different investigations, but rather to the difficulty of comparing different conditions. To illustrate what I mean by one example: An aluminum cable strung at Stanford in a grassy field and another strung at Pit after being dragged over the sharp lava rocks should be expected to give different losses near the critical voltage. It would be difficult to predict the result of the mutilation by the lava beds without direct measurements.
- Published
- 1925
17. Short Paper: The subaerial setting of the Ordovician Borrowdale Volcanic Group, English Lake District
- Author
-
Michael J. Branney
- Subjects
Volcanic rock ,geography ,Paleontology ,geography.geographical_feature_category ,Volcano ,Pyroclastic surge ,Lava ,Subaerial ,Subaerial eruption ,Ordovician ,Geology ,Unconformity - Abstract
Most Ordovician volcanic rocks of southern Britain were produced in volcanic island settings and the Borrowdale Volcanic Group (BVG) of the Lake District has traditionally been interpreted in this way. However, a review of lithofacies associations in the BVG indicates a subaerial environment. Pyroclastic surge deposits, thin welded tuff beds, lava flow morphologies, abundant erosional unconformities, and fluviatile and laharic facies indicate widespread subaerial emplacement. Volcano-tectonic subsidence aided preservation of subaerial facies, although a preservation bias favoured lacustrine deposits. Erosional unconformities above subaerial aggradational volcanic sequences are to be expected, so the sub-Windermere Group unconformity does not necessarily imply tectonic uplift.
- Published
- 1988
18. Fractionation Processes in Deccan Traps Magmas: Comments on the Paper by G. Sen--Mineralogy and Petrogenesis of the Deccan Trap Lava Flows Around Mahabaleshwar, India
- Author
-
K.G. Cox and Colin W. Devey
- Subjects
Trap (computing) ,Geophysics ,Geochemistry and Petrology ,Lava ,Geochemistry ,Fractionation ,Deccan Traps ,Petrology ,Geology ,Petrogenesis - Published
- 1987
19. Insect conservation in early succession on islands: lessons from Surtsey, Iceland, and the Krakatau Archipelago, Indonesia
- Author
-
New, T. R. and New, T. R., editor
- Published
- 2008
- Full Text
- View/download PDF
20. The morphology and surface features of olivine in kimberlite lava: implications for ascent and emplacement mechanisms.
- Author
-
Jones, T. J., Russell, J. K., Porritt, L. A., and Brown, R. J.
- Subjects
OLIVINE ,KIMBERLITE ,LAVA ,PERIDOTITE ,INCLUSIONS in igneous rocks ,SURFACE texture ,IMAGE analysis - Abstract
Many kimberlite rocks contain large proportions of ellipsoidal-shaped xenocrystic olivine grains that are derived mainly from the disaggregation of peridotite. Xenocrystic olivine grains from a lava erupted from the Quaternary Igwisi Hills kimberlites, Tanzania, are compared to phenocrystic olivine, liberated from picritic lavas, and mantle olivine, liberated from a fresh peridotite xenolith, in order to examine the potential modification of olivine surface textures due to transport from the mantle to the surface within kimberlite magmas. Image analysis, SEM imagery and laser microscopy reveals significant differences in the surface features and morphologies of the three crystal populations. Xenocrystic olivine grains are characterised by rough surfaces, ellipsoidal shapes and impact pits. Mantle olivines are characterised by flaked surfaces and indented shapes consistent with growth as a crystal aggregates. Phenocrystic olivines are smooth-surfaced and exhibit flat crystal faces. We infer that the distinctive shapes and surfaces of xenocrystic olivine grains resulted from three distinct mechanical processes attending their rapid transport from their source in the mantle lithosphere: (1) penetrative flaking from micro-tensile failure induced by rapid decompression; (2) sustained abrasion and attrition arising from particle-particle collisions between grains in a turbulent, volatile-rich flow regime, and; (3) higher energy particle-particle collisions that produced impact cavities superimposed on decompression structures. The combination of these processes during the rapid ascent of kimberlite magmas is responsible for the distinctive ellipsoidal shape of olivine xenocrysts found in kimberlites worldwide. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
21. Utility of Stack-of-stars Acquisition for Hepatobiliary Phase Imaging without Breath-holding
- Author
-
Shintaro Ichikawa, Hiroshi Onishi, Tetsuya Wakayama, Kang Wang, Ali Ersoz, Daiki Tamada, Marie-Luise Kromrey, Ty A Cashen, and Utaroh Motosugi
- Subjects
Lava ,Image quality ,Portal vein ,Streak ,Contrast Media ,Hepatic Veins ,030218 nuclear medicine & medical imaging ,respiratory navigation ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Image Processing, Computer-Assisted ,Humans ,Radiology, Nuclear Medicine and imaging ,stack-of-stars ,breath-hold ,Retrospective Studies ,medicine.diagnostic_test ,hepatobiliary phase ,business.industry ,Respiratory motion ,Magnetic resonance imaging ,Magnetic Resonance Imaging ,gadoxetic acid ,Stars ,Liver ,Hepatobiliary phase ,Nuclear medicine ,business ,Artifacts ,030217 neurology & neurosurgery ,Major Paper - Abstract
Purpose: Post-contrast liver magnetic resonance imaging is typically performed with breath-hold 3D gradient echo sequences. However, breath-holding for >10 s is difficult for some patients. In this study, we compared the quality of hepatobiliary phase (HBP) imaging without breath-holding using the prototype pulse sequences stack-of-stars liver acquisition with volume acceleration (LAVA) (LAVA Star) with or without navigator echoes (LAVA Starnavi+ and LAVA Starnavi−) and Cartesian LAVA with navigator echoes (Cartesian LAVAnavi+). Methods: Seventy-two patients were included in this single-center, retrospective, cross-sectional study. HBP imaging using the three LAVA sequences (Cartesian LAVAnavi+, LAVA Starnavi−, and LAVA Starnavi+) without breath-holding was performed for all patients using a 3T magnetic resonance system. Two independent radiologists qualitatively analyzed (overall image quality, liver edge sharpness, hepatic vein clarity, streak artifacts, and respiratory motion/pulsation artifacts) HBP images taken by the three sequences using a five-point scale. Quantitative evaluations were also performed by calculating the liver-to-spleen, -lesion, and -portal vein (PV) signal intensity ratios. The results were compared between the three sequences using the Friedman test. Results: LAVA Starnavi+ showed the best image quality and hepatic vein clarity (P < 0.0001). LAVA Starnavi− showed the lowest image quality (P < 0.0001–0.0106). LAVA Starnavi+ images showed fewer streak artifacts than LAVA Starnavi− images (P < 0.0001), while Cartesian LAVAnavi+ images showed no streak artifacts. Cartesian LAVAnavi+ images showed stronger respiratory motion/pulsation artifacts than the others (P < 0.0001). LAVA Starnavi− images showed the highest liver-to-spleen ratios (P < 0.0001–0.0005). Cartesian LAVAnavi+ images showed the lowest liver-to-lesion and -PV ratios (P < 0.0001–0.0108). Conclusion: In terms of image quality, the combination of stack-of-stars acquisition and navigator echoes is the best for HBP imaging without breath-holding.
- Published
- 2019
22. Clusterisation and Temporal Trends of Heat Flux by UAS Thermal Camera.
- Author
-
Marotta, Enrica, Peluso, Rosario, Avino, Rosario, Avvisati, Gala, Bellucci Sessa, Eliana, Belviso, Pasquale, Caputo, Teresa, Carandente, Antonio, Cirillo, Francesca, and Pescione, Romano Antonio
- Subjects
HEAT flux ,CAMERAS ,VOLCANOES ,CALDERAS ,LAVA - Abstract
Analysis of a series of thermal mappings obtained by UAS flights on quiescent volcanoes requires some special techniques to be performed. The main challenge is represented by the difficulty of separating hot and cold pixels in areas where their temperatures are quite similar. This task is indeed much simpler, for example, for lava flows where the temperature differences between the hot lava and the cold soil is rather big. This paper shows various software developed in order to perform this extraction and calculate the trends over time of both the average temperature and the heat flux from the soil. This prototypal implementation used thermal flights performed over a time span of a few years on an area in the Campi Flegrei caldera in southern Italy. Standard image manipulation techniques were used to segmentate and clusterise each thermal mapping in order to reduce the thermal anomalies to some sets of simpler features characterised by their fundamental parameters. The temporal trends of some physical parameters (temperature, heat flux, etc.) were extracted from these sets, and we found interesting results necessary for correlations and for ongoing research with other parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
23. Correlations on the southern Kaapvaal Craton Margin, 1: Ventersdorp lavas transgressed the Doornberg lineament.
- Author
-
Cornell, D. H., Meintjes, P. G., van der Westhuizen, W. A., and Kristoffersen, M.
- Subjects
ZIRCON ,STRATIGRAPHIC correlation ,LAVA ,SHEAR zones ,CONTINENTAL margins ,URANIUM-lead dating ,RUTILE - Abstract
Two small exposures of quartz-porphyritic rocks occur on the farm Zoutpekel 98 in the Marydale Terrane between the Doornberg Fault and Brakbos Shear Zone, apparently overlying Kaapvaal basement granite but lacking clear field relationships due to sand and Dwyka tillite cover. They are lavas and tuffs, metamorphosed in lower amphibolite facies. They contain quartz phenocrysts with a distinctive blue colour, due to metamorphic exsolution of rutile. Microbeam U-Pb zircon dating gives a combined 207Pb/206Pb age of 2 722 ± 3 Ma (seven determinations on four samples), interpreted as the age of extrusion. Three of these samples give the same discordia upper intercept age, but one sample gives discordia intercepts of 2 688 ± 15 and 1 223 ± 120 Ma, thought to reflect metamorphic lead loss related to the ~1 210 Ma Namaqua terrane assembly collisions. The Zoutpekel exposures are coeval with the 2 720 ± 2 Ma Makwassie Formation of the Platberg Group, Ventersdorp Supergroup. They also correspond geochemically to the Makwassie Formation and no other unit of the supergroup. A sample from the T'kuip Formation of the nearest Ventersdorp Supergroup inlier on the Kaapvaal Craton (east of the Doornberg Fault), gives an age of 2 716 ± 8 Ma, also confirming its lithostratigraphic and geochemical correlation with the Makwassie Formation. The Zoutpekel exposures show that not only the Kaapvaal basement granites, but also the supracrustal cover rocks of the Ventersdorp Supergroup, extend southwards across the Doornberg Fault, The Marydale Terrane is thus not an exotic terrane, but probably represents a passive continental margin developed at the beginning of the 1 300 to 1 000 Ma Namaqua-Natal Wilson cycle. The age range of the Ventersdorp Supergroup and the age and stratigraphic correlation of the Marydale Group thrust complex, which straddles the Zoutpekel exposures, will be investigated in two companion papers. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
24. Vascular plant colonisation of Surtsey Island (1965-1990) - a dataset
- Author
-
Valgeir Bjarnason, Bjartmar Sveinbjörnsson, Skúli Þ Magnússon, Sigurður H Richter, Ágúst H Bjarnason, Eyþór Einarsson, Ragnar Jónasson, Pawel Wasowicz, Jón Guðmundsson, Sally Thorsteinsson, and Borgþór Magnússon
- Subjects
0106 biological sciences ,Vascular plant ,010504 meteorology & atmospheric sciences ,Lava ,colonisation ,Iceland ,01 natural sciences ,Ecology & Environmental sciences ,lcsh:QH301-705.5 ,Ecosystem development ,Primary succession ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,geography ,Surtsey ,volcanism ,geography.geographical_feature_category ,Ecology ,biology ,primary succession ,010604 marine biology & hydrobiology ,biology.organism_classification ,Data Paper (Biosciences) ,Colonisation ,Europe ,Angiospermae ,lcsh:Biology (General) ,Disturbance (ecology) ,Volcano ,Biogeography ,Northern Atl ,Archipelago ,Northern Atlantic - Abstract
The process of ecosystem development over time that takes place on a new substrate devoid of biological activity (such as, for example, lava) is called primary succession. Research on primary succession is not easy, as it is limited to rare occasions when a piece of land totally lacking in any pre-existing life occurs. The emergence of volcanic islands is such an occasion; it is a unique event that allows a natural experiment in the study of colonisation processes and primary succession. Surtsey (located in the Vestmannaeyar archipelago off the southern coast of Iceland) is an iconic example of a place where primary succession has been studied for decades and where human disturbance has been minimised due to significant geographic isolation and early protection efforts. Here, we present a georeferenced dataset of vacular plant occurrences collected during the field studies carried out on Surtsey Island during the first three decades of its existence. To date, no dataset containing plant distribution data documenting the process of early stages of colonisation of Surtsey has been published. What is more, to our knowledge, there is no other dataset that can be compared with our Surtsey data that is readily available for researchers working on plant colonisation dynamics and primary succession processes. Here, we present a complete, geo-referenced dataset of all plant occurrences (10,094 in total) collected on Surtsey between 1965 and 1990.
- Published
- 2020
25. Comment on paper: ‘Morphology and compositions of spinel in Pu′u ′Ō′ō lava (1996–1998), Kilauea volcano, Hawaii′—enigmatic discrepancies between lava and gas-based fO2 determinations of Pu′u ′Ō′ō lava
- Author
-
Gerlach, T.M.
- Published
- 2004
- Full Text
- View/download PDF
26. Early Eocene A-type (ferroan) rhyolites in southwestern Tibet: A far-field tectonic effect of the India–Eurasia collision.
- Author
-
Li, Chenwei, Li, Zhijun, Zeng, Min, and Stern, Robert J.
- Subjects
IGNEOUS rocks ,PETROLOGY ,GEOLOGICAL time scales ,ISOTOPE geology ,LAVA ,EOCENE Epoch ,ZIRCON - Abstract
Eocene igneous rocks along the Gangdese belt in southern Tibetan Plateau are important for understanding the India–Eurasia collision and Tibetan Plateau uplift. These magmatic rocks are widely considered to be related to roll-back or break-off of the Neotethyan slab during northward subduction. However, Eocene rhyolites in the northwestern Gangdese belt (SW Qiangtang margin) do not fit either the rollback or breakoff models. This paper investigates these Early Eocene lavas and compares them with contemporaneous igneous rocks along the Gangdese belt via detailed field observations, petrology, zircon geochronology, zircon Lu–Hf isotopes and whole-rock geochemistry. These felsic lavas form large outcrops in western Tibet and have two zircon U–Pb ages of 54.71 ± 0.14 Ma and 54.74 ± 0.27 Ma. They have high SiO
2 and alkali contents, FeO*/MgO, and Ga/Al ratios as well as strongly negative Eu anomalies and slightly positive zircon εHf(t) values (+2.5 to +4.4). Both Ti-in-zircon and Zr saturation thermometers confirm high magmatic temperatures (~900°C). They are ferroan, A-type rhyolites. Furthermore, the distinctive low εHf(t) values imply that these rhyolites are likely partial melting products of the southwestern Qiangtang Terrane. The lithosphere in this region undergone long-term shortening and thickening since 80–95 Ma. Pre-thickened lithosphere may be a prerequisite for the Early Eocene delamination, and the simultaneous inducement is a far-field tectonic effect from the India–Eurasia collision. We suggest that: (1) India collided with Eurasia before 55 Ma and triggered delamination to form the Shiquanhe A-type rhyolites on the southwestern Qiangtang margin thereafter; and (2) tectonic stresses related to India–Eurasia collision during the Eocene were transmitted efficiently over large distances. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
27. Performance of Micro-Polluted Source Water Treatment by Biological Aerated Filter with Lava Media
- Author
-
Kang Xie, Li Ping Qiu, Li Xin Zhang, and Bin Wang
- Subjects
Hydraulic retention time ,Media filter ,Lava ,Chemistry ,Biofilter ,Environmental engineering ,General Medicine ,Aeration ,Turbidity ,Pulp and paper industry ,Permanganate index ,Filter (aquarium) - Abstract
The performance of biological aerated filter (BAF) with lava media for the treatment of micro-polluted source water was investigated with the operational temperature 18°C, the PH value 6.29-8.35, hydraulic retention time (HRT) 30 min as well as dissolved oxygen (DO) 2-3mg/L. The results show that the lava media is a pretty carrier that has promising surface characteristics for microorganism growth and biofilm formation. The biofilter could be operated successfully in 18d, that was shorter than the ceramic and zeolite media filter in the same start-up condition. During the steady operation period, the lava media BAF performed a promising treatment performance of permanganate index, ammonia nitrogen, and turbidity removal, where as the removal rate were 46%, 97% and 62%, respectively. Moreover, the index of UV254, which partly indicates the concentration of hardly degradable substance in the micro-polluted source water, could be removed 23% in the novel media filter.
- Published
- 2014
28. Deciphering magmatic processes from plagioclase, clinopyroxene and amphibole chemistry and textures: A case study of a basaltic lava flow in the Basque-Cantabrian Basin (Northern Spain).
- Author
-
Pesquera, Alfonso and Gil-Crespo, Pedro P.
- Subjects
- *
LAVA flows , *PLAGIOCLASE , *AMPHIBOLES , *LAVA , *ILMENITE , *MAGMAS - Abstract
This paper addresses the study of a pillow lava interbedded with Late Albian-Early Cenomanian sediments that crops out in Armintza (Bizkaia, Northern Spain). The lava flow is an alkaline basalt with abundant macrocrysts of clinopyroxene, kaersutite, Ca-rich plagioclase (50-86% An) and ilmenite, which display a variety of textures and complex zoning patterns indicative of open-system magmatic behaviour. Macrocryst cores are likely to be inherited antecrysts that underwent complex processes under deep pre-eruptive conditions (≈ 700-800 MPa). Microcrysts and macrocryst rims formed during magmatic ascent and emplacement at shallower levels (≈ 35 MPa). Hypothetical melts in equilibrium with clinopyroxenes and amphiboles have trace element compositions like metasomatic vein melts containing amphibole, and their patterns overlap with those of the Armintza pillow lava. This suggests a metasomatised lithospheric mantle with amphibole-rich veins as a potential source for the alkaline basaltic melt. It is even conceivable that the Armintza pillow lava and other alkaline volcanic manifestations of the Basque-Cantabrian Basin were part of the same magma plumbing system through which a series of time-limited eruptions of different batches of magma ascended from the lithospheric mantle to the upper crust during the Albian to the Santonian. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
29. When the lava meets the sea: emplacement of the 2–4 ka San Bartolo lava flow field, Stromboli volcano (Italy).
- Author
-
Shajahan, Rasia, Harris, Andrew J. L., Zanella, Elena, Gurioli, Lucia, Test, Claudio Robustelli, Calvari, Sonia, and Drovanti, Lodovico
- Subjects
- *
VOLCANIC fields , *LAVA flows , *VOLCANOES , *BODIES of water , *LAVA , *MAGNETIC measurements - Abstract
When a lava flow enters a body of water, either a lake, sea, river or ocean, explosive interaction may arise. However, when it is an 'a'ā lava flow entering water, a more complex interaction occurs, that is very poorly described and documented in literature. In this paper, we analysed the 2–4 ka San Bartolo lava flow field emplaced on the north flank of Stromboli volcano, Italy. The lava flow field extends from ~ 650 m a.s.l. where the eruptive fissure is located, with two lava channels being apparent on the steep down to the coast. Along the coast the lava flow field expands to form a lava delta ~ 1 km wide characterised by 16 lava 'Flow' units. We performed a field survey to characterise the features of lava entering the sea and the associated formation of different components and magnetic measurements to infer the flow fabrics and emplacement process of the lava flow system. We measured the density, porosity and connectivity of several specimens to analyse the effect of lava-water interaction on the content in vesicles and their connectivity and conducted a macroscopic componentry analysis (clast count) at selected sites to infer the character of the eroded offshore segment of the lava flow field and its component flow units. The collected data allowed us to define the main components of a lava delta fed by 'a'ā lava flows, with its channels, littoral units, ramps, lava tubes, and inflated pāhoehoe flows controlled by the arterial 'a'ā flow fronts. The spatial organisation of these components allowed us to build a three-step descriptive model for 'a'ā entering a water. The initial stage corresponds to the entry of channel-fed 'a'ā lava flow into the sea which fragments to form metric blocks of 'a'ā lava. Continued lava supply to the foreshore causes flow units to stall while spreading over this substrate. Subsequent 'a'ā lava flow units ramp up behind the stalled flow front barrier. Lava tubes extending through the stalled flow barrier feed the seaward extension of a bench made of several pāhoehoe flow units. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. The History of the Formation of Pliocene–Quaternary Valley Lava Rivers in the Northeast Part of the Javakheti Volcanic Highland, Lesser Caucasus.
- Author
-
Parfenov, A. V., Lebedev, V. A., Vashakidze, G. T., Yakushev, A. I., and Ediberidze, B. D.
- Subjects
VALLEYS ,VOLCANIC eruptions ,UPLANDS ,LAVA flows ,LAVA ,MAGMATISM - Abstract
This paper presents new results from geological-stratigraphic and isotope geochronological studies of young lavas in the northeast part of the Javakheti Highland, Lesser Caucasus, Georgia. We provide a first description of the Algeti complex-structured valley lava flow about 55 km in total length; no information on this feature is available in the geological literature. We show that young magmatism in the northeast part of the Javakheti region has been evolving in the time interval of 3.2–1.5 Ma B.P. Its earlier phases have produced the longest (up to 100 km) valley basaltic lava river of those known in the Lesser Caucasus (the Khrami flow) (3.19 ± 0.10 Ma B.P.). Subsequently (2.7–2.5 Ma B.P.), the eruptions continued to form extensive lava plateaus there (Tsalka, Gomareti, and other plateaus). In the Late Piacentian–Early Gelasian (2.7–2.0 Ma B.P.) the active vents in the northern Javakheti Range started to form the Algeti basaltoid valley flow, with this process lasting for ~1 Ma. The terminal phase of its formation (1.9–1.5 Ma B.P.) was probably related to eruptions of the volcanic cones in the area of Lake Tabatskuri. These data, along with the reconstruction of the history of young magmatism, enabled us to trace the main patterns in the generation of the present-day relief and the network of river valleys in the area of study in the Lesser Caucasus. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
31. Three-Dimensional Numerical Modeling of Lava Dynamics Using the Smoothed Particle Hydrodynamics Method.
- Author
-
Starodubtsev, I. S., Starodubtseva, Y. V., Tsepelev, I. A., and Ismail-Zadeh, A. T.
- Subjects
LAVA domes ,THREE-dimensional modeling ,HYDRODYNAMICS ,LAVA flows ,VOLCANIC eruptions ,LAVA - Abstract
Lava domes and lava flows are major manifestations of effusive volcanic eruptions. Less viscous lava tends to flow long distances depending on the volcanic slope topography, the eruption rate, and the viscosity of the erupted magma. When magma is highly viscous, its eruption to the surface leads to the formation of lava domes and their growth. The meshless smoothed particle hydrodynamics (SPH) method is used in this paper to simulate lava dynamics. We describe the SPH method and present a numerical algorithm to compute lava dynamics models. The numerical method is verified by solving a model of cylindrical dam-break fluid flow, and the modelled results are compared to the analytical solution of the axisymmetric thin-layer viscous current problem. The SPH method is applied to study three models of lava advancement along the volcanic slope, when the lava viscosity is constant, depends on time and on the volume fraction of crystals in the lava. Simulation results show characteristic features of lava flows, such as lava channel and tube formation, and lava domes, such as the formation of a highly viscous carapace versus a less viscous dome core. Finally, the simulation results and their dependence on a particle size in the SPH method are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
32. Radar Observation of the Lava Tubes on the Moon and Mars.
- Author
-
Qiu, Xiaohang and Ding, Chunyu
- Subjects
GROUND penetrating radar ,LAVA ,MARTIAN surface ,MARS (Planet) ,RADAR ,TUBES - Abstract
The detection of lava tubes beneath the surfaces of the Moon and Mars has been a popular research topic and challenge in planetary radar observation. In recent years, the Moon–based ground penetrating radar (GPR) carried by the Chinese Chang'e–3/–4 mission, the RIMFAX radar carried by the Mars mission Perseverance, and the RoSPR radar and MOSIR radar carried by China's Tianwen–1 orbiter have extensively promoted the exploration of the underground space of extraterrestrial bodies, which is crucial for the future utilization and development of these spaces. This paper expounds on the principles, methods, and detection results of using GPR to detect lava tubes on the Moon and Mars. First, lava tubes' formation mechanism and morphological characteristics are outlined, followed by an introduction to GPR's working principles and classification. The advantages, disadvantages, and prospects of different types of radar in detecting the lava tubes are analyzed. Finally, the distribution of lava tubes on the Moon and Mars is briefly summarized, and the potential utilization of lava tubes is discussed. We believe that the GPR technique is an effective geophysical method for exploring the underground structures of the Moon and Mars, and the lava tubes beneath the surface of extraterrestrial bodies can provide important references for selecting future Moon and Mars bases. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
33. Conditions and Magmas Sources of the Summit and Flank Eruptions of Klyuchevskoy Volcano in 2020–2021: Isotope (Sr–Nd–Pb–O)-geochemical data.
- Author
-
Cherkashin, R. I., Bergal-Kuvikas, O. V., Chugaev, A. V., Larionova, Yu. O., Bindeman, I. N., Khomchanovsky, A. L., and Plutakhina, E. Yu.
- Subjects
VOLCANIC eruptions ,LAVA ,MAGMAS ,ISOTOPES ,VOLCANISM ,VOLCANOES - Abstract
In 2021, a unique event occurred on Klyuchevskoy volcano (Kamchatka). After over 30-year prevalence of summit eruptions, a flank vent was formed. It was named after the Corresponding Member of the USSR Academy of Sciences G.S. Gorshkov. The eruption began immediately after the end of the summit crater activation in 2020–2021 at an altitude of 2850 m in the northwestern part of the volcano, where manifestations of flank volcanism were not observed earlier. This paper presents geochemical and isotopic Sr–Nd–Pb–O data on lavas of the summit and flank eruptions of Klyuchevskoy volcano in 2020–2021. A comparative petrographic analysis was carried out and the chemical composition of the Ol, Cpx, and Pl phenocrysts in these lavas was analyzed. The lavas of both eruptions are alumina andesitic basalts of normal alkalinity. Variations of major oxides in the lavas of the summit eruption and G.S. Gorshkov vent are SiO
2 53.1–53.2 wt % and 51.6–53.2 wt %, MgO 5.6 wt % and 5.5–6.0 wt %; respectively. Temperature and pressure estimates showed that plagioclase crystallization occurred at 1210–1118°С and 12.3–3.6 kbar in lavas of the summit eruption and at 1203–1119°С and 9.0–3.3 kbar in lavas of the flank vent. The contents of major elements, similar conditions of plagioclase generations and compositional variations of Ol, Cpx, and Pl phenocrysts in the lavas of both eruptions indicate a genetic relationship of the magmas that fed the summit and flank eruptions. The lavas of the 2016 and 2020–2021 summit eruptions, as well as the lavas of the previous summit eruptions of Klyuchevskoy volcano are characterized by the persistent Sr–Nd–Pb isotopic characteristics:87 Sr/86 Sr = 0.703625–0.703626,143 Nd/144 Nd = 0.513085–0.513102,206 Pb/204 Pb = 18.3148–18.3179. Isotopic ratios207 Pb/204 Pb (15.5022–15.5107) and208 Pb/204 Pb (37.9597–38.0143) are significantly higher for the lavas of the last summit and flank eruptions than for all Klyuchevskoy lavas of the past eruptions, which indicates more complex magma evolution at crustal levels. The values of δ18 O = 6.49–7.39‰ (SMOW)-in the lavas of the considered eruptions are consistent with previously published data on Klyuchevskoy volcano. The lavas of the Gorshkov vent are enriched with Ba, Zr, Sr and other incompatible elements at constant MgO values in comparison with the lavas of the last summit eruptions, which points to the different evolutionary paths of their magmas. Sharply increased values of the87 Sr/86 Sr ratio (0.703673–0.703743) in the lavas of the G.S. Gorshkov vent, which were not previously observed in the lavas of Klyuchevskoy volcano, testify to the intense crustal assimilation of initial melts in the northwestern part of the volcano. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
34. New Data on the Rock and Mineral Composition of Kharchinsky and Zarechny Volcanoes, Central Kamchatka Depression: Heterogeneity of the Mantle Source and Peculiarities of Magma Evolution in the Crust.
- Author
-
Gorbach, N. V., Nekrylov, N. A., Portnyagin, M. V., and Hoernle, K.
- Subjects
MINERALS ,MAGMAS ,PLAGIOCLASE ,PHENOCRYSTS ,VOLCANOES ,ADAKITE ,LAVA - Abstract
Kharchinsky and Zarechny volcanoes and the Kharchinsky Lake zone of monogenic cones are unique eruptive centers of magnesian lavas located above the northern margin of the Pacific plate subducting beneath Kamchatka. This paper presents new geochemical data on the composition of rocks (55 samples) and minerals (over 900 analyses of olivine, pyroxenes, amphibole, and plagioclase) of these centers analyzed by XRF and LA-ICP-MS (rocks) and electron microprobe (minerals). Most of the studied rocks are magnesian (Mg# = 60–75 mol %) medium-K basalts and basaltic andesites. Moderate-magnesian (Mg# = 52–59 mol %) basaltic andesites are present among the monogenic cones of Kharchinsky Lake. The rare rock varieties include the high-K basalts–basaltic andesites of dikes in the center of Kharchinsky volcano and the magnesian andesites (Mg# = 58–61 mol %) of the extrusions of Zarechnу volcano. The distribution of trace-element contents in these samples demonstrates enrichment in large-ion lithophile elements and light REEs at depletion in high field strength elements and heavy REEs, as is typical of arc rocks. The high-K basalts and basaltic andesites show anomalous enrichment in Ba (>1000 ppm), Th (>3.8 ppm), U (>1.8 ppm), Sr (> 800 ppm, Sr/Y > 50), and light REE (La > 20 ppm), and their compositions are close to those of low-Si adakites. The basalts and basaltic andesites contain phenocrysts of high-Mg olivine (up to Fo
92.6 ) and clinopyroxene (Mg # up to 91 mol %). The rocks show petrographic and geochemical evidence of fractional crystallization, along with the processes of mineral accumulation and magma mixing. Some of the olivine phenocrysts show high NiO contents (up to 5000 ppm) and an elevated Fe/Mn ratio (up to 80), which were interpreted as evidence of the participation of a pyroxenite source in the magma generation processes. The use of the Ca/Fe and Ni/Mg ratios allowed us to distinguish the composition fields and evolution trends of olivine associated with different sources: peridotite and pyroxenite, which were formed by a reaction between mantle-wedge peridotites and high-Si melts of the subducted oceanic crust. The new data are consistent with other lines of evidence of melting of the subducted Pacific plate edge beneath the northern part of the Central Kamchatka Depression at the Kurile–Kamchatka and Aleutian subduction zone junction and testify to a significant heterogeneity of the mantle in this area. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
35. The Volcanism Occurring during the Initial Phase of Formation of the Northern Subduction Segment in the Pacific Plate (Kamchatka Peninsula, Kumroch Range).
- Author
-
Tolstykh, M. L., Babansky, A. D., Smirnova, M. D., Pevzner, M. M., Lebedev, V. A., Larionova, Yu. O., Kushcheva, Yu. V., and Parfenov, A. V.
- Subjects
SUBDUCTION ,VOLCANISM ,URANIUM ,LAVA ,RADIOACTIVITY ,PENINSULAS ,ANDESITE ,THORIUM - Abstract
The present paper reports a study of rocks in Mts. Baidara and Semkorok, which are situated in the northwestern flank of the Kumroch Range. The rocks are Amf-Px basaltic andesites and andesites, and are characterized by an arc type of trace element distribution. Some mineralogical and geochemical features in the composition of lavas sampled at Mt. Baidara (low concentrations of K
2 O, as well as of the entire range of REEs, of large-ion elements, thorium, and uranium) and at Mt. Semkorok (low concentrations of light REEs) are substantially different from the rocks of the adjacent Shiveluch Late Pleistocene–Holocene volcanic massif. The K-Ar isotopic lava ages are ~0.7 Ma (Baidara) and ~1.3 Ma (Semkorok), suggesting the inference that the eruptions might be related to the initial phase in the formation of the northern subduction segment in the Pacific plate. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
36. Impact of Media Type and Various Operating Parameters on Nitrification in Polishing Biological Aerated Filters
- Author
-
Rao Y. Surampalli, Jeong Hyub Ha, and Say Kee Ong
- Subjects
Ammonia ,chemistry.chemical_compound ,Environmental Engineering ,Hydraulic retention time ,Chemistry ,Lava ,Chemical oxygen demand ,Environmental engineering ,Plastic pipework ,Nitrification ,Aeration ,Pulp and paper industry ,Effluent - Abstract
Three biological aerated filters (BAFs) composed of a PVC pipe with a diameter of 75 mm were constructed and operated at a waste - water temperature at 13°C. The media used for each BAF were: 5-mm gravel; 5-mm lava rock; 12.5-mm diameter by 15-mm long plastic rings, all with a media depth of 1.7 m. The feedwater, which simulated the effluent of aerated lagoons, had influent soluble chemical oxygen demand (sCOD) and ammonia concentrations of approximately 50 and 25 mg/L, respectively. For a hydraulic retention time (HRT) of two hours without recirculation, ammonia percent removals were 98.5, 98.9, and 97.8%, for the gravel, lava rock, and plastic rings, respectively. By increasing the effluent recirculation from 100 to 200% for an HRT of one hour, respective ammonia removals im - proved from 90.1 to 96, 76.5 to 90, and 65.3 to 79.5% for gravel, lava rock, and plastic rings. Based on the ammonia and sCOD loadings for different HRTs, the estimated maximum ammonia loading was approximately 0.6 kg NH 3 -N/m 3 -day for the three BAFs of different media types. The zero-order biotransformation rates for the BAF with gravel were found to be higher than the lava rock and plastic ring media. The results ultimately showed that BAF can be used as an add-on system to aerated lagoons or as a secondary treatment unit to meet ammonia discharge limits.
- Published
- 2010
37. Muon radiography and deformation analysis of the lava dome formed by the 1944 eruption of Usu, Hokkaido —Contact between high-energy physics and volcano physics
- Author
-
Izumi Yokoyama and Hiroyuki Tanaka
- Subjects
geography ,Original Paper ,geography.geographical_feature_category ,Lateral eruption ,Lava ,muon radiography ,Resurgent dome ,deformation analysis ,Physics ,General Physics and Astronomy ,Lava dome ,General Medicine ,Volcanic Eruptions ,Physical Phenomena ,Radiography ,Dome (geology) ,Effusive eruption ,Volcano ,Japan ,Stratovolcano ,structure of lava dome ,General Agricultural and Biological Sciences ,Geology ,Seismology - Abstract
Lava domes are one of the conspicuous topographic features on volcanoes. The subsurface structure of the lava dome is important to discuss its formation mechanism. In the 1944 eruption of Volcano Usu, Hokkaido, a new lava dome was formed at its eastern foot. After the completion of the lava dome, various geophysical methods were applied to the dome to study its subsurface structure, but resulted in a rather ambiguous conclusion. Recently, from the results of the levelings, which were repeated during the eruption, “pseudo growth curves” of the lava dome were obtained. The curves suggest that the lava dome has a bulbous shape. In the present work, muon radiography, which previously proved effective in imaging the internal structure of Volcano Asama, has been applied to the Usu lava dome. The muon radiography measures the distribution of the “density length” of volcanic bodies when detectors are arranged properly. The result obtained is consistent with the model deduced from the pseudo growth curves. The measurement appears to afford useful method to clarify the subsurface structure of volcanoes and its temporal changes, and in its turn to discuss volcanic processes. This is a point of contact between high-energy physics and volcano physics.
- Published
- 2008
38. Detailed 40Ar/39Ar Geochronology of the Loyalty and Three Kings Ridges Clarifies the Extent and Sequential Development of Eocene to Miocene Southwest Pacific Remnant Volcanic Arcs.
- Author
-
Gans, P. B., Mortimer, N., Patriat, M., Turnbull, R. E., Crundwell, M. P., Agranier, A., Calvert, A. T., Seward, G., Etienne, S., Durance, P. M. J., Campbell, H. J., and Collot, J.
- Subjects
ISLAND arcs ,GEOLOGICAL time scales ,EOCENE Epoch ,ARGON-argon dating ,MIOCENE Epoch ,SUBMARINE volcanoes ,LAVA - Abstract
The 2015 VESPA voyage (Volcanic Evolution of South Pacific Arcs) was a seismic and rock dredging expedition to the Loyalty and Three Kings Ridges and South Fiji Basin. In this paper we present 33 40Ar/39Ar, 22 micropaleontological, and two U/Pb ages for igneous and sedimentary rocks from 33 dredge sites in this little‐studied part of the southwest Pacific Ocean. Igneous rocks include basalts, dolerites, basaltic andesites, trachyandesites, and a granite. Successful Ar/Ar dating of altered and/or low‐K basalts was achieved through careful sample selection and processing, detailed petrographic and element mapping of groundmass, and incremental heating experiments on both phenocryst and groundmass separates to interpret the complex spectra produced by samples having multiple K reservoirs. The 40Ar/39Ar ages of most of the sampled lavas, irrespective of composition, are latest Oligocene to earliest Miocene (25–22 Ma); two are Eocene (39–36 Ma). The granite has a U/Pb zircon age of 23.6 ± 0.3 Ma. 40Ar/39Ar lava ages are corroborated by microfossil ages from associated sedimentary rocks. The VESPA lavas are part of a >3,000 km long disrupted belt of Eocene to Miocene subduction‐related volcanic rocks. The belt includes arc rocks in Northland New Zealand, Northland Plateau, Three Kings Ridge, and Loyalty Ridge and, speculatively, D'Entrecasteaux Ridge. This belt is the product of superimposed Eocene and Oligocene‐Miocene remnant volcanic arcs that were stranded along and near the edge of Zealandia while still‐active arc belts migrated east with the Pacific trench. Plain Language Summary: Samples of lava from the seabed between New Zealand and New Caledonia have been dated using atomic clocks and fossils. Most lavas erupted in a big pulse of volcanic activity between 25 and 22 million years ago. They are part of a belt of now‐extinct undersea volcanoes that stretches for more than 3,000 km between New Zealand and the Solomon Islands. These volcanoes were formed by subduction of the Pacific Plate under the Australian Plate. Key Points: A major pulse of 25–22 Ma volcanism is documented on the Loyalty and Three Kings Ridges, southwest Pacific OceanThe ridges are part of a more than 3,000 km long belt of Eocene to Miocene remnant volcanic arcs, stranded along the edge of ZealandiaWith care in sample selection, and petrological work, meaningful Ar/Ar ages can be obtained from altered and/or very low‐K submarine basalts [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
39. PORE SYSTEM QUANTIFICATION AND CHARACTERIZATION IN VOLCANIC ROCKS: A CASE STUDY FROM THE LOWER CRETACEOUS SERRA GERAL GROUP, PARANÁ BASIN, SOUTHERN BRAZIL.
- Author
-
Becker, M., Lima, E. F., Waichel, B. L., and Mantovani, I. F.
- Subjects
VOLCANIC ash, tuff, etc. ,HYDROCARBON reservoirs ,X-ray computed microtomography ,CARBONATE rocks ,IGNEOUS provinces ,PARAGENESIS ,LAVA - Abstract
Studies of pore systems in volcanic rocks are of increasing importance due to these rocks' potential as reservoirs for hydrocarbons. For this paper, samples of basaltic pahoehoe, rubbly pahoehoe and acidic lava from the Lower Cretaceous Serra Geral Group (Paraná Basin, southern Brazil) were analysed in order to quantify and characterize the constituent pore systems. The Serra Geral Group volcanics were erupted as part of the Paraná‐Etendeka Igneous Province in the Early Cretaceous (Valanginian – Hauterivian). Analyses included experimental measurements by permo‐porosimeter integrated with X‐ray microtomography (μ‐CT) image analysis of vertical and horizontal sample plugs. In addition petrographic analyses were carried out to characterize pore types in thin section. The experimental porosity values ranged from 0.11 to 13.08% and most permeability values were generally lower than 0.0004 mD. Values varied as much within flow zones as they did between them. Porosity and permeability values were not sufficient for the Serra Geral Group volcanics to be considered as a potential reservoir analogue. However the wide range in values was attributed to the processes which controlled the origin and development of the pore system. Primary pores observed included intracrystalline sieve, vesicular and interflow laminar types; secondary porosity, such as spongy, interclast and intra‐matrix pore types, was related to dissolution and the precipitation of secondary minerals. The porosity values obtained by μ‐CT (between <0.01 and 3.37%) were lower than those experimentally measured by permo‐porosimeter. This was attributed to the presence of multi‐scale pores in the volcanic rocks sampled, and also to limitations with image resolution. Even so, the use of μ‐CT allowed the visualization of porosity variations and was useful in characterizing the pore system. The results presented in this paper demonstrate that the volcanic rocks in the Serra Geral Group have a heterogeneous pore system, similar to that in carbonate rocks. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
40. An interpretative view of open-vent volcanoes.
- Author
-
Vergniolle, S. and Métrich, N.
- Subjects
ACQUISITION of data ,MAGMAS ,LAVA ,VOLCANOES - Abstract
Open-vent volcanoes are special systems where the dynamics of sustained magmatic processes can be thoroughly investigated and where new monitoring tools can be tested and applied. However, various aspects remain puzzling at open-vent volcanoes for which forecasting their behaviour can be an important challenge. Recent papers highlight the very rapid improvements in spaceborne instruments, data acquisition techniques, data treatment and modelling over the last decade and illustrate the fundamental contribution of long time-series data, either discontinuous or continuous, and the development of multiparameter studies. Here we provide an interpretative overview of the main characteristics of open-vent volcanoes on the basis of selected examples chosen to be representative of the diversity of their magma composition, their eruptive activity and their geodynamic context. We choose typical open-vent volcanoes (Stromboli, Yasur and Erebus), some of them hosting a lava lake (Erta 'Ale, Nyiragongo, Villarrica, Ambrym and Masaya), to those with vigourous activity, which are associated to a long-lasting eruption (Arenal, Fuego, Popocatépetl, Santiaguito). We briefly review their surface activity and report the values of SO
2 flux and the derived magma supply rate with emphasis on the key results found on their behaviour. We show the key role of the magma viscosity and its implication on the degassing. We present the current models used to explain how an open-vent volcano could be maintained, such as by the simultaneous rise and fall of a degassing and degassed magma (bi-directional flow models) and the few thermal models at lava lakes and in the conduit. Finally, we discuss the sulphur evolution for three nearby volcanoes at the triple junction in Central America (Pacaya, Fuego, Santiaguito). [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
41. MATHEMATICAL MODELING APPLIED TO THE ANALYSIS OF MAGMATIC INTRUSIONS THERMAL INFLUENCE IN PARANÁ BASIN.
- Author
-
RODRIGUES DE OLIVEIRA, BRUNO, CORVAL, ARTUR, DE CASTRO VALENTE, SERGIO, LAMBERT, WANDERSON JOSÉ, ALBUQUERQUE MIRANDA, ALAN WANDERLEY, SOUZA DE OLIVEIRA, LUIZ GABRIEL, and FERNANDES, VICTOR HUGO
- Subjects
IGNEOUS intrusions ,MATHEMATICAL models ,SILLS (Geology) ,LAVA ,PETROLEUM industry ,HEAT ,PETROLEUM ,DIKES (Geology) - Abstract
This paper has the objective to present equations capable of generating one-dimensional models that permit to quantify the thermal influence caused by igneous intrusions. In Paraná Basin, the petroleum systems were great influenced by igneous activities in which they are presented by a thick lava effusion, large number of dykes in the entire sedimentary section and various levels of sills intruded in stratifications to provide thermal energy for organic maturation. Thus, a better understanding of how and how much the intrusions affect the generation of oil and gas is extremely necessary since the knowledge related to the effects of intrusions in such atypical petroleum system is still insufficient. The obtained results show: the thermal influence caused by igneous intrusions is much higher than that proposed in the literature; the greater the number of intrusions and the thicker they are, the thermal influence is unfavorable at short distances and favorable at large distances. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
42. Sketching Rilles (Lava Channels)
- Author
-
Thomas McCague, Erika Rix, Deirdre Kelleghan, Richard Handy, and Sally Russell
- Subjects
Basalt ,Graben ,Tectonics ,Lava ,Paper towel ,Rille ,Crust ,Petrology ,Extensional definition ,Geology - Abstract
Whether they are straight, arcuate, or sinuous, rimae (rilles) appear to be channels, which may be the result of faulting, lava flows, collapsed lava tubes, or extensional tectonic processes such as occurrences when basin-forming impacts were later filled with dense basaltic lavas. Straight rilles are frequently grabens, a collapsed floor between two parallel faults that can extend for hundreds of kilometers. Arcuate rilles are often found around the margins of maria when the stress of the cooling mass of basalt lava faulted the crust in concentric arcs. Sinuous rilles resulted when flowing lava formed channels or tubes that, when emptied or collapsed, revealed the snaking path of the lava caused by the differential velocity of the flow.
- Published
- 2011
43. Structure and Composition of the Nadayansky Lava Flow: an Example of the Homogeneity of Lava Flows of the Siberian Trap Province.
- Author
-
Krivolutskaya, N. A. and Kedrovskaya, T. B.
- Subjects
LAVA flows ,VOLCANIC ash, tuff, etc. ,FLOOD basalts ,TRACE elements ,WATERSHEDS ,HOMOGENEITY ,LAVA - Abstract
The Nadayansky Flow is one of the main markers of the volcanic pile of the Siberian Trap Province and covers an area of approximately 48 000 km
2 at an average thickness of 30 to 50 m. The paper is the first to present data demonstrating the constancy of the major- and trace-element composition of the Nadayansky Flow, typifying basalt lava flows in the province. The flow makes up the bottom part of the Mokulaevsky Formation in the Norilsk area and the bottom of the Khonnamansky Formation at the Putorana Plateau and, correspondingly, overlies the Morongovsky and Ayansky formations (the names of these formations differ because they are used in different schemes for the stratigraphic subdivision of the volcanic rock sequence). The rocks show an obvious glomerophyric texture, which makes this flow clearly distinguishable from the under- and overlying rock units. The composition of the Nadayansky Flow was studied throughout its length of a few hundred kilometers and shows very little varying concentrations of major components (48.31 SiO2 , 1.26 TiO2 , 15.8 Al2 O3 , 12.71 Fe2 O3 , 0.19 MnO, 6.89 MgO, 11.1 CaO, 2.25 Na2 O, 0.37 K2 O, 0.14 P2 O5 , 0.02 Cr2 O3 ) and trace elements (2.44 La/Sm and 1.56 Gd/Yb), whose variations are within the analytical uncertainties (XRF and ICP-MS analyses). The basalt of the flow crystallized from tholeiitic melt, whose composition was analogous to those of melts that produced all other flows of the Mokulaevsky Formation. For comparison, the paper displays the inner structures of the underlying Morongovsky and Mokulaevsky formations in the basin of the Mikchangda River in the eastern part of the Norilsk area. The composition of the basalts of these formations also varies insignificantly. The main difference is an increase in TiO2 concentration from 1.19 to 1.3 wt % with the transition from the lower formation to the upper one. In spite of the insignificant difference between the concentrations, it is of principal importance and makes it possible to distinguish between the basalts of these formations. The detected constancy of the compositions of the formations as a whole and the Nadayansky Flow in particular are principally important for studying continental flood basalt provinces and demonstrates the compositional homogeneity of the erupted magmas and their sources. These results are important as an example how geochemical data can be used to correlate widely spaced sequences of volcanic rocks. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
44. A photographic atlas of the architecture, low geometry and morphology, and facies of the Serra Geral Group (Paraná Igneous Province) in the state of Paraná, Brazil.
- Author
-
LICHT, OTAVIO BONI and ARIOLI, EDIR EDEMIR
- Subjects
FACIES ,VOLCANISM ,ROCKS ,LAVA - Abstract
Copyright of Boletim Paranaense de Geociências is the property of Universidade Federal do Parana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2020
- Full Text
- View/download PDF
45. A Volcano in the Alps?
- Author
-
Ioganson, L. I.
- Subjects
VOLCANOES ,VOLCANIC eruptions ,EIGHTEENTH century ,NUMBER theory ,LAVA ,FOREIGN study - Abstract
This paper analyzes the article published in Sankt-Peterburgskie Vedomosti (SPV) and a number of foreign studies addressing the natural cataclysm that occurred in Savoy (Western Alps) in 1751 and was recognized by witnesses as a volcanic eruption. This event was observed by V. Donati, a famous natural sc-ientist of the 18th century, and described by H.B. de Saussure, a prominent researcher of the Alps. Other evidence of similar phenomena in the Alps is presented from the historical data. It is suggested that a special type of explosive eruption, not accompanied by lava pouring out but still very dangerous may occur in the Alps. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
46. Hematology and Biochemistry of the Española Lava Lizard (Microlophus delanonis).
- Author
-
Capobianco, Christian M., Clarke, Emma A., Muñoz-Pérez, Juan Pablo, Ruales, Daniela Alarcón, Loyola, Andrea, Ayala, Stuart Torres, Skehel, Alice L., Guzmán, Kimberly E., Valle, Carlos A., and Lewbart, Gregory A.
- Subjects
- *
LAVA , *LIZARDS , *BIOCHEMISTRY , *FERAL cats , *HEMATOLOGY - Abstract
This paper presents novel baseline health parameters on the Española lava lizard (Microlophus delanonis). Blood samples and morphological measurements were taken on 51 lizards (21 males, 30 females) captured from three locations on the island of Española. Morphological parameters measured included body weight, snout–vent length, and temperature. Blood samples were analyzed approximately 8 h after collection using an i-STAT portable blood analyzer that measured hemoglobin, total CO2, glucose, lactate, sodium, potassium, and ionized calcium. Hematologic characterization data were obtained using standard laboratory techniques. There were significant differences found in snout–vent length, weight, heart rate, respiratory rate, total CO2, and heterophil percentage between males and females. The data presented herein can be used to monitor the health of this population of Española lava lizards as well as help to understand the health of a related species, the San Cristóbal lava lizard (Microlophus bivittatus), which faces different evolutionary pressures including the presence of humans and feral cats. This study continues to widen our understanding of the genus Microlophus; however, further research should characterize the remaining species that inhabit the islands in the Galápagos archipelago. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
47. Comparison between Automated and Manual Detection of Lava Fountains from Fixed Monitoring Thermal Cameras at Etna Volcano, Italy.
- Author
-
Calvari, Sonia and Nunnari, Giuseppe
- Subjects
FOUNTAINS ,LAVA ,VOLCANOES ,IMAGE analysis ,THERMAL imaging cameras ,LAVA flows ,INFRARED cameras - Abstract
The Etna volcano is renowned worldwide for its extraordinary lava fountains that rise several kilometers above the vent and feed eruptive columns, then drift hundreds of kilometers away from the source. The Italian Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) is responsible for the monitoring of Mt. Etna, and for this reason, has deployed a network of visible and thermal cameras around the volcano. From these cameras, INGV-OE keeps a keen eye, and is able to observe the eruptive activity, promptly advising the civil protection and aviation authorities of any changes, as well as quantifying the spread of lava flows and the extent of pyroclastic and ash plumes by using a careful analysis of the videos recorded by the monitoring cameras. However, most of the work involves analysis carried out by hand, which is necessarily approximate and time-consuming, thus limiting the usefulness of these results for a prompt hazard assessment. In addition, the start of lava fountains is often a gradual process, increasing in strength from Strombolian activity, to intermediate explosive activity, and eventually leading to sustained lava fountains. The thresholds between these different fields (Strombolian, Intermediate, and lava fountains) are not clear cut, and are often very difficult to distinguish by a manual analysis of the images. In this paper, we presented an automated routine that, when applied to thermal images and with good weather conditions, allowed us to detect (1) the starting and ending time of each lava fountain, (2) the area occupied by hot pyroclasts, (3) the elevation reached by the lava fountains over time, and (4) eventually, to calculate in real-time the erupted volume of pyroclasts, giving results close to the manual analysis but more focused on the sustained portion of the lava fountain, which is also the most dangerous. This routine can also be applied to other active volcanoes, allowing a prompt and uniform definition of the timing of the lava fountain eruptive activity, as well as the magnitude and intensity of the event. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
48. Quaternary Collision-Zone Magmatism of the Greater Caucasus.
- Author
-
Bewick, Samuel, Parkinson, Ian J, Harris, Nigel, Adamia, Shota, Sadradze, Nino, Allen, Mark B, and Hammond, Sam
- Subjects
MAGMATISM ,TRACE elements ,LAVA ,VOLCANIC ash, tuff, etc. ,ISOTOPIC signatures ,CONTINENTAL crust ,ISOTOPE geology - Abstract
The Greater Caucasus mountains (Cavcasioni) mark the northern margin of the Arabia–Eurasia collision zone. Magmatism in the central part of the Greater Caucasus began in the Pleistocene, up to ~25 Myr after initial collision. This paper presents bulk-rock and Sr–Nd–Pb isotope geochemistry from 39 Quaternary volcanic rock samples (<450 Ka) recovered from the Mt. Kazbek (Kasbegui) region of the Greater Caucasus, Georgia, to assess the sources and magmatic evolution of these lavas and the possible triggers for melting in the context of their regional tectonics. Compositions are dominantly calc-alkaline basaltic andesite to dacite (57–67 wt % SiO
2 ). Although the lavas were erupted through thick continental crust, there is little evidence for extensive modification by crustal contamination. Trace element and isotopic systematics indicate that the lavas have supra-subduction zone signatures, most likely reflecting derivation from a lithospheric source that had been modified by melts and/or fluids from material subducted before and during the collisional event. Mass-balance modelling of the Sr–Nd isotope data indicates that the lavas require significant input from a subducted slab, with deep-sourced fluids fluxing the slab into the source region. In contrast with published data from Lesser Caucasus magmatism, data from the Mt. Kazbek region suggest that a compositionally distinct sediment source resides beneath the Greater Caucasus, producing characteristic trace element and Pb isotopic signatures. Two distinct compositional groups and therefore primary liquids can be discerned from the various volcanic centres, both derived from light rare-earth element enriched sources, but with distinct differences in Th/Yb and Dy/Yb ratios and Pb isotopes. Rare-earth element modelling of the lava sources is consistent with 3–4% melting starting in the garnet peridotite and continuing into the spinel facies or, potentially, sited in the garnet-spinel transition zone. Small-scale convection related to mantle upwelling provides a plausible mechanism for Greater Caucasus magmatism and explains the random aspect to the distribution of magmatism across the Arabia–Eurasia collision zone. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
49. Lavascape: legal spectacle at Kīlauea.
- Author
-
Marusek, Sarah
- Subjects
LAVA ,SEMIOTICS (Law) ,GEOGRAPHY ,ENVIRONMENTAL regulations ,LANDSCAPES - Abstract
In considering the theme "Exploring Legal Discourse: A Sociosemiotic (Re)Construction," this paper examines the symbolic relationship between law and chaos in the changing landscape of Kīlauea Volcano on Hawai'i Island. The socio-legal dimensions of this relationship provide insight into law's project of governance in the dynamic natural environment. Most recently, in the summer of 2018, lava spouted and then flowed from Kīlauea in over twenty-four fissures which opened up within two heavily populated residential subdivisions. Law's response to the ensuing chaos provides keen insight into the epistemological positionality of law toward nature. In an attempt to tame this enlivened lavascape of persons and lava, law asserts authority over the spectacle in the areas of sightseeing, access, and mapping. In other words, the legal spectacle of lava eruption is an attempt to jurisdictionally frame the legal imagination of human risk in this dynamic landscape through legal semiotics, legal materiality, and legal topology. However, as this paper will explore, the source of chaos is actually law itself. Attempts to manage chaos are actually attempts to manage human nature as visitation to the erupting volcanic environment is ultimately beyond law's complete control. In a larger sense, this study of Kīlauea's lavascape as a constructed legal spectacle illustrates the phenomenological framing of law's incomplete jurisdiction over kinetic environments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. Age of the magma chamber and its physicochemical state under Elbrus Greater Caucasus, Russia using zircon petrochronology and modeling insights.
- Author
-
Bindeman, I. N., Melnik, O. E., Guillong, M., Utkin, I. S., Wotzlaw, J.-F., Schmitt, A. K., and Stern, R. A.
- Subjects
ZIRCON ,MAGMAS ,IMAGING systems in seismology ,AGE distribution ,DACITE ,SPATIAL resolution ,LAVA - Abstract
Mount Elbrus, Europe's tallest and largely glaciated volcano, is made of silicic lavas and is known for Holocene eruptions, but the size and state of its magma chamber remain poorly constrained. We report high spatial resolution U–Th–Pb zircon ages, co-registered with oxygen and hafnium isotopic values, span ~ 0.6 Ma in each lava, documenting magmatic initiation that forms the current edifice. The best-fit thermochemical modeling constrains magmatic fluxes at 1.2 km
3 /1000 year by hot (900 °C), initially zircon-undersaturated dacite into a vertically extensive magma body since ~ 0.6 Ma, whereas a volcanic episode with eruptible magma only extends over the past 0.2 Ma, matching the age of oldest lavas. Simulations explain the total magma volume of ~ 180 km3 , temporally oscillating δ18 O and εHf values, and a wide range of zircon age distributions in each sample. These data provide insights into the current state (~ 200 km3 of melt in a vertically extensive system) and the potential for future activity of Elbrus calling for much-needed seismic imaging. Similar zircon records worldwide require continuous intrusive activity by magmatic accretion of silicic magmas generated at depths, and that zircon ages do not reflect eruption ages but predate them by ~ 103 to 105 years reflecting protracted dissolution–crystallization histories. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.