Inter-eruptive Periods Research Articles

Interpretation of neovolcanic versus palaeovolcanic sand grains: an example from Miocene deep‐marine sandstone of the Topanga Group (Southern California)

ABSTRACTDespite abundant data on volcaniclastic sand(stone), the compositional, spatial and temporal distribution of volcanic detritus within the sedimentary record is poorly documented. One of the most intricate tasks in optical analysis of sand(stone) containing volcanic particles is to distinguish grains derived by erosion of ancient volcanic rocks (i.e. palaeovolcanic, noncoeval grains) from grains generated by active volcanism (subaqueous and/or subaerial) during sedimentation (neovolcanic, coeval grains).Deep‐marine volcaniclastic sandstones of the Middle Topanga Group of southern California are interstratified with 3000‐m‐thick volcanic deposits (both subaqueous and subaerial lava and pyroclastic rocks, ranging from basalt, andesite to dacite). These rocks overlie quartzofeldspathic sandstones (petrofacies 1) of the Lower Topanga Group, derived from deep erosion of a Mesozoic magmatic arc.Changes in sandstone composition in the Middle Topanga Group provide an example of the influence of coeval volcanism on deep‐marine sedimentation. Volcaniclastic strata were deposited in deep‐marine portions of a turbidite complex (volcaniclastic apron) built onto a succession of intrabasinal lava flows and on the steep flanks of subaerially emplaced lava flows and pyroclastic rocks.The Middle Topanga Group sandstones are vertically organized into four distinctive petrofacies (2–5). Directly overlying basalt and basaltic‐andesite lava flows, petrofacies 2 is a pure volcanolithic sandstone, including vitric, microlitic and lathwork volcanic grains, and neovolcanic crystals (plagioclase, pyroxene and olivine). The abundance of quenched glass (palagonite) fragments suggests a subaqueous neovolcanic provenance, whereas sandstones including andesite and minor basalt grains suggest subaerial neovolcanic provenance. This petrofacies probably was deposited during syneruptive Periods, testifying to provenance from both intrabasinal and extrabasinal volcanic events. Deposited during intereruptive periods, impure volcanolithic petrofacies 3 includes both neovolcanic (85%) and older detritus derived from plutonic, metamorphic and palaeovolcanic rocks. During post‐eruptive periods, the overlying quartzofeldspathic petrofacies 4 and 5 testify to progressive decrease of neovolcanic detritus (48–14%) and increase of plutonic‐metamorphic and palaeovolcanic detritus.The Upper Topanga Group (Calabasas Formation), conformably overlying the Middle unit, has dominantly plutoniclastic sandstone (petrofacies 6). Neovolcanic detritus is drastically reduced (4%) whereas palaeovolcanic detritus is similar to percentages of the Lower Topanga Group (petrofacies 1).In general, the volcaniclastic contribution represents a well‐defined marker in the sedimentary record. Detailed compositional study of volcaniclastic strata and volcanic particles (including both compositional and textural attributes) provides important constraints on deciphering spatial (extrabasinal vs. intrabasinal) and temporal relationships between neovolcanic events (pre‐, syn‐, inter‐ and post‐eruptive periods) and older detritus.

Mechanisms of crustal uplift and subsidence at the Yellowstone caldera, Wyoming

Leveling surveys in 1923, 1976, and each year from 1983 to 1993 have shown that the east-central part of the Yellowstone caldera, near the base of the Sour Creek resurgent dome, rose at an average rate of 14±1 mm/year from 1923 to 1976 and 22±1 mm/year from 1976 to 1984. In contrast, no detectable movement occurred in the same area from 1984 to 1985 (-2±5 mm/year), and from 1985 to 1993 the area subsided at an average rate of 19±1 mm/year. We conclude that uplift from 1923 to 1984 was caused by: (1) pressurization of the deep hydrothermal system by fluids released from a crystallizing body of rhyolite magma beneath the caldera, then trapped beneath a self-sealed zone near the base of the hydrothermal system; and (2) aseismic intrusions of magma into the lower part of the sub-caldera magma body. Subsidence since 1985 is attributed to: (1) depressurization and fluid loss from the deep hydrothermal system, and (2) sagging of the caldera floor in response to regional crustal extension. Future intrusions might trigger renewed eruptive activity at Yellowstone, but most intrusions at large silicic calderas seem to be accommodated without eruptions. Overpressurization of the deep hydrothermal system could conceivably result in a phreatic or phreatomagmatic eruption, but this hazard is mitigated by episodic rupturing of the self-sealed zone during shallow earthquake swarms. Historical ground movements, although rapid by most geologic standards, seem to be typical of inter-eruption periods at large, mature, silicic magma systems like Yellowstone. The greatest short-term hazards posed by continuing unrest in the Yellowstone region are: (1) moderate to large earthquakes (magnitude 5.5–7.5), with a recurrence interval of a few decdes; and (2) small hydrothermal explosions, most of which affect only a small area (<0.01 km2), with a recurrence interval of a few years.

124. Interpretation of intereruption period of Mount Erebus : A mechanism of Strombolian eruptions(Abstracts of Papers Presented at the Spring Meeting of the Society)

124. Interpretation of intereruption period of Mount Erebus : A mechanism of Strombolian eruptions(Abstracts of Papers Presented at the Spring Meeting of the Society)

Statistical analysis of persistent explosive activity at stromboli, 1971: Implications for eruption prediction

In September 1971 three vents within the summit crater of the volcano Stromboli intermittently ejected molten lava and hot gas to heights of several hundred meters. Field observations were conducted over four consecutive days (5–8 September 1971) and a chronological record of 399 discrete eruptions was compiled. Frequency distributions of intereruption (repose) periods at each vent can be statistically represented by a normal (Gaussian) distribution at the 99.9% confidence level. This implies that the eruption triggering mechanism operating at each vent is a completely random process, if the vents are individually considered to be independent volcanic systems. Regression analysis of the complete chronological record reveals, however, that the length of a vent's repose period is generally correlated with the number of eruptions occurring at the other two summit vents. Such intercorrelations can be used to increase the accuracy of eruption predictions by 18–87% compared with eruption forecasts that simply anticipate the average repose period between successive eruptions at each vent. The results of this study imply that in the case of persistent explosive activity at several vents, it may be possible to predict the outbreak of individual eruptions quite accurately on the basis of parameters reflecting the nature and intensity of eruptions occurring at other vents. In addition, intercorrelations between the explosive activity occurring at several active vents can be used to develop physical models of subsurface volcanic systems.

The distribution of minor elements in the rocks of Sakura-jima volcano

Geochemical and crystallochemical relationships in the lavas and pyroclastics of Sakura-jima volcano, Japan, suggest that magmatic differentiation is the dominant fractionation process. A triangular diagram is shown for Na-K-Ca and total Fe—Mg—Na + K. The volcanics investigated are the Kitadake, Minamidake, unknown eruption epoch, 1468–1476, 1779, 1914, 1946 flows, and 1955–1958 pyroclastics. Trends are illustrated in Cr, Mg, Ca, V, Fe, Si, Al, Ga and O in modified Larsen diagrams. Various ionic ratios, especially V/Fe, show marked variation on the modified Larsen plot. From the 1468–1476 until the 1914 eruptions, the Sakura-jima lavas tend to become more mafic. From 1946 until 1958, there is a tendency to become more silicic. However, within the 1955–1958 volcanic sequence, Co, Cr and V increases suggest increasing mafic differentiation of the lavas and pyroclastics. Distinct and extreme anomalies occur in Co, Cr and V in the initial pulse of a given eruption within the 1955–1958 sequence. During the initial high energy eruptive phase, expulsion of mafic differentiates (enriched in Co, Cr, and V) consolidated in the volcanic throat is thought to account for these high concentrations. Pb is also enriched in the early eruptive phases in the 1955–1958 volcanic series. Volcanic sublimates accumulating during the inter-eruptive period in the pyroclastic material within the volcano may account for this phenomenon. Spectroscopic analyses for Ga, Ni, Co, Cr, V, Pb, and Sn are given for sixty-two samples.

The Volcanoes and Rocks of Pantelleria

Previous articleNext article FreeThe Volcanoes and Rocks of PantelleriaHenry S. WashingtonHenry S. Washington Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 21, Number 8Nov. - Dec., 1913 Article DOIhttps://doi.org/10.1086/622118 Views: 126Total views on this site Citations: 9Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Silvio G. Rotolo, Stéphane Scaillet, Fabio Speranza, John C. White, Rebecca Williams, Nina J. Jordan Volcanological evolution of Pantelleria Island (Strait of Sicily) peralkaline volcano: a review, Comptes Rendus. Géoscience 353, no.S2S2 (Jan 2022): 111–132.https://doi.org/10.5802/crgeos.51David Oldroyd, Davis Young Of the American Quantitative Igneous Rock Classification: Part 5, Earth Sciences History 31, no.11 (Jan 2013): 1–41.https://doi.org/10.17704/eshi.31.1.17660412784m64r4Don F. Parker, John C. White Large-scale silicic alkalic magmatism associated with the Buckhorn Caldera, Trans-Pecos Texas, USA: comparison with Pantelleria, Italy, Bulletin of Volcanology 70, no.33 (Jun 2007): 403–415.https://doi.org/10.1007/s00445-007-0145-2M. Mattia, A. Bonaccorso, F. Guglielmino Ground deformations in the Island of Pantelleria (Italy): Insights into the dynamic of the current intereruptive period, Journal of Geophysical Research 112, no.B11B11 (Nov 2007).https://doi.org/10.1029/2006JB004781Benedetto De Vivo, Maria Luce Frezzotti, Gail Mahood Fluid inclusions in xenoliths yield evidence for fluid evolution in peralkaline granitic bodies at Pantelleria (Italy), Journal of Volcanology and Geothermal Research 52, no.44 (Oct 1992): 295–301.https://doi.org/10.1016/0377-0273(92)90050-NGail A Mahood, James A Stimac Trace-element partitioning in pantellerites and trachytes, Geochimica et Cosmochimica Acta 54, no.88 (Aug 1990): 2257–2276.https://doi.org/10.1016/0016-7037(90)90050-UG Longworth, S.E Warren The application of Mössbauer spectroscopy to the characterisation of western mediterranean obsidian, Journal of Archaeological Science 6, no.22 (Jun 1979): 179–193.https://doi.org/10.1016/0305-4403(79)90061-X O. F. Tuttle Origin of the Contrasting Mineralogy of Extrusive and Plutonic Salic Rocks, The Journal of Geology 60, no.22 (Sep 2015): 107–124.https://doi.org/10.1086/625943W. C. Smith A Classification of some Rhyolites, Trachytes, and Phonolites from part of Kenya Colony, with a Note on some Associated Basaltic Rocks, Quarterly Journal of the Geological Society 87, no.1-41-4 (Feb 1931): 212–258.https://doi.org/10.1144/GSL.JGS.1931.087.01-04.10