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  • Institute of Physics  (137,469)
  • American Geophysical Union  (28,944)
  • Cambridge University Press
  • 2005-2009  (166,484)
  • 1955-1959  (9,468)
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  • 1
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    January 2002 volcano-tectonic eruption of Nyiragongo volcano, Democratic Republic of Congo (2007)
    American Geophysical Union
    Details
    Publication Date: 2024-05-09
    Description: In January 2002, Nyiragongo volcano erupted 14–34 × 106 m3 of lava from fractures on its southern flanks. The nearby city of Goma was inundated by two lava flows, which caused substantial socioeconomic disruption and forced the mass exodus of the population, leaving nearly 120,000 people homeless. Field observations showed marked differences between the lava erupted from the northern portion of the fracture system and that later erupted from the southern part. These observations are confirmed by new 238U and 232Th series radioactive disequilibria data, which show the presence of three different phases during the eruption. The lavas first erupted (T1) were probably supplied by a residual magma batch from the lava lake activity during 1994–1995. These lavas were followed by a fresh batch erupted from fissure vents as well as later (May–June 2002) from the central crater (T2). Both lava batches reached the surface via the volcano's central plumbing system, even though a separate flank reservoir may also have been involved in addition to the main reservoir. The final phase (T3) is related to an independent magmatic reservoir located much closer (or even beneath) the city of Goma. Data from the January 2002 eruption, and for similar activity in January 1977, suggest that the eruptive style of the volcano is likely to change in the future, trending toward more common occurrence of flank eruptions. If so, this would pose a significant escalation of volcanic hazards facing Goma and environs, thus requiring the implementation of different volcano-monitoring strategies to better anticipate where and when future eruptions might take place.
    Description: Published
    Description: B09202
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Nyiragongo ; forecasting ; volcanic hazard ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Combating footnote status in evolutionary theory (2005)
    Cambridge University Press
    In:  Biased embryos and evolution vol. 74, 1/2, pp. 209-211
    Details
    Publication Date: 2024-01-12
    Keywords: evolution ; natural selection ; variation ; developmental bias
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/review
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  • 3
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    Comparison of different ridge formation models of Arctic Sea ice with observations from laser profiling (2006)
    International Glaciological Society | Cambridge University Press
    Details
    Publication Date: 2024-01-07
    Description: Sea ice deforms under convergent and Shear motion, causing rafting and ridging. This results in thicker ice than could be formed by thermodynamic growth only. Three different approaches to Simulating the formation of pressure ridges in a dynamic–thermodynamic continuum model are considered. They are compared with and evaluated by airborne laser profiles of the Sea-ice Surface roughness. The respective characteristic of each of the three ridging Schemes is (1) a prognostic equation for deformation energy from which ridge parameters are derived; (2) a redistribution function, Shifting ice between two categories, level and ridged, combined with a Monte Carlo Simulation for ridge parameters; and (3) prognostic equations for ridge density and height, resulting in the formation of ridged-ice volume. The model results Show that the ridge density is typically related to the State of ice motion, whereas the mean Sail height is related to the parent ice thickness. In general, all of the three models produce realistic distributions of ridges. Finally, the Second ridging Scheme is regarded as the most appropriate for climate modelling, while the third Scheme has advantages in Short-term Sea-ice forecasting.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    The paroxysmal event and its deposits (2008)
    American Geophysical Union
    Details
    Publication Date: 2023-01-16
    Description: The 5 April 2003 eruption of Stromboli volcano (Italy) was the most violent in the past 50 years. It was also the best documented due to the accurate geophysical monitoring of the ongoing effusive eruption. Detailed field studies carried out a few hours to a few months after the event provided further information that were coupled with visual documentation to reconstruct the explosive dynamics. The eruption consisted of an 8-min-long explosive event preceded by a short-lived precursory activity that evolved into the impulsive ejection of gas and pyroclasts. Meter-sized ballistic blocks were launched to altitudes of up to 1400 m above the craters falling on the volcano flanks and on the village of Ginostra, about 2 km far from the vent. The vertical jet of gas and pyroclasts above the craters fed a convective plume that reached a height of 4 km. The calculated erupted mass yielded values of 1.1–1.4 × 108 kg. Later explosions generated a scoria flow deposit, with an estimated mass of 1.0–1.3 × 107 kg. Final, waning ash explosions closet the event. The juvenile fraction consisted of an almost aphyric, highly vesicular pumice mingled with a shallow-derived, crystal-rich, moderately vesicular scoria. Resuming of the lava emission a few hours after the paroxysm indicate that the shallow magmatic system was not significantly modified during the explosions. Combination of volume data with duration of eruptive phases allowed us to estimate the eruptive intensity: during the climactic explosive event, the mass discharge rate was between 106 and 107 kg/s, whereas during the pyroclastic flow activity, it was 2.8–3.6 × 105 kg/s. Strong similarities with other historical paroxysms at Stromboli suggest similar explosion dynamics.
    Description: Unpublished
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: open
    Keywords: Stromboli ; paroxysm ; explosive dynamics ; pyroclastic deposits ; ballistic ejecta ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 5
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    Arctic decadal variability from an idealized atmosphere-ice-ocean model: 1. Model description, calibration, and validation (2006)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C06028, doi:10.1029/2004JC002821.
    Description: This paper describes a simple “multibox” model of the Arctic atmosphere-ice-ocean system. The model consists of two major modules (an Arctic module and a Greenland Sea module) and several sub-modules. The Arctic module includes a shelf box model coupled with a thermodynamic sea ice model, and an Arctic Ocean model coupled with a sea ice model and an atmospheric box model. The Greenland Sea module includes an oceanic model coupled with a sea ice model and a statistical model of surface air temperature over the Greenland Sea. The full model is forced by daily solar radiation, wind stress, river runoff, and Pacific Water inflow through Bering Strait. For validation purposes, results from model experiments reproducing seasonal variability of the major system parameters are analyzed and compared with observations and other models. The model reproduces the seasonal variability of the Arctic system reasonably well and is used to investigate decadal Arctic climate variability in Part 2 of this publication.
    Description: This publication is the result of research sponsored by Alaska Sea Grant with funds from the National Oceanic and Atmospheric Administration Office of Sea Grant, Department of Commerce, under grant no. NA 86RG0050 (project no. GC/01-02), and from the University of Alaska with funds appropriated by the state. This research has also been supported by the National Science Foundation and by the International Arctic Research Center, University of Alaska Fairbanks, under auspices of the United States National Science Foundation.
    Keywords: Arctic decadal oscillations ; Idealized Arctic model ; Arctic–Greenland Sea interaction
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Gravity currents from a dam-break in a rotating channel (2005)
    Cambridge University Press
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Cambridge University Press, 2005. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 536 (2005): 253-283, doi:10.1017/S0022112005004544.
    Description: The generation of a gravity current by the release of a semi-infinite region of buoyant fluid of depth $H$ overlying a deeper, denser and quiescent lower layer in a rotating channel of width $w$ is considered. Previous studies have focused on the characteristics of the gravity current head region and produced relations for the gravity current speed $c_{b}$ and width $w_b$ as a functions of the local current depth along the wall $h_b$, reduced gravity $g^\prime$, and Coriolis frequency $f$. Here, the dam-break problem is solved analytically by the method of characteristics assuming reduced-gravity flow, uniform potential vorticity and a semigeostrophic balance. The solution makes use of a local gravity current speed relation $c_{b} \,{=}\, c_b(h_b,\ldots)$ and a continuity constraint at the head to close the problem. The initial value solution links the local gravity current properties to the initiating dam-break conditions. The flow downstream of the dam consists of a rarefaction joined to a uniform gravity current with width $w_b$ (${\le}\, w$) and depth on the right-hand wall of $h_b$, terminated at the head moving at speed $c_b$. The solution gives $h_b$, $c_b$, $w_b$ and the transport of the boundary current as functions of $w/L_R$, where $L_R \,{=}\, \sqrt{g^\prime H}/f$ is the deformation radius. The semigeostrophic solution compares favourably with numerical solutions of a single-layer shallow-water model that internally develops a leading bore. Existing laboratory experiments are re-analysed and some new experiments are undertaken. Comparisons are also made with a three-dimensional shallow-water model. These show that lateral boundary friction is the primary reason for differences between the experiments and the semigeostrophic theory. The wall no-slip condition is identified as the primary cause of the experimentally observed decrease in gravity current speed with time. A model for the viscous decay is developed and shown to agree with both experimental and numerical model data.
    Description: This work was supported by NSF Grants OCE-0095059 and OCE-0132903.
    Keywords: Gravity current ; Dam-break problem
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Locations of selected small earthquakes in the Zagros mountains (2006)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q03001, doi:10.1029/2004GC000849.
    Description: The Zagros mountains of southern Iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between Arabia and Eurasia. Due to the lack of dense local seismic or geodetic networks, the inferred kinematics of the collision in Iran is mainly based on catalogs of teleseismically determined earthquake locations. We surveyed all M w 〉 4.5 earthquakes in the Harvard Centroid Moment Tensor (HCMT) and International Seismological Centre (ISC) catalogs that occurred in the Zagros mountains during the period 1992–2002 and that were spanned by Interferometric Synthetic Aperture Radar (InSAR) images from the ERS 1 and 2 satellites. We invert the observed deformation for the best fitting point source, single fault plane, and distributed fault slip for four earthquakes and one unexplained deformation event. We find that we can precisely locate earthquakes that are too small to be well-located by either the HCMT or ISC catalogs, allowing us to tie specific earthquakes to active geologic structures.
    Description: ERS 1 and 2 data were acquired through an ESA category-1 proposal. R. Lohman is partially supported by a NASA New Investigator Program grant award to M. Simons.
    Keywords: DOAS ; SO2 emissions
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Rapid analysis of 13C in plant-wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments (2006)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 5 (2004): Q10004, doi:10.1029/2004GC000772.
    Description: Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular waxes produced by terrestrial higher plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total plant-wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular plant origin (〈C25) are removed by evaporation on the moving wire. Test samples processed using this procedure yielded n-alkane fractions essentially free of interfering components. The δ13C values obtained by MW-irMS did not differ significantly from weighted averages of individual n-alkane δ13C values obtained by irmGC-MS. Isotopic variations in compound-class n-alkane fractions from a latitudinal transect of core-top sediments from the Southwest African margin (3°N–28°S) were congruent with those measured by compound-specific isotopic analyses of plant-wax n-alkanes. The amplitude of the variations was smaller, indicating contributions from non-plant-wax hydrocarbons, but the measurements revealed variations in carbon isotopic composition that are consistent with vegetation zones on the adjacent continent.
    Description: We thank the WHOI Summer Student Fellow program and NSF (BCS-0218511) for funding.
    Keywords: Moving wire ; Plant-wax n-alkanes ; Stable carbon isotopes
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Intraseasonal variability near 10°N in the eastern tropical Pacific Ocean (2006)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C05015, doi:10.1029/2005JC002989.
    Description: New in situ observations from 10°N, 125°W during 1997–1998 show strong intraseasonal variability in meridional velocity and sea surface temperature. The 50- to 100-day oscillations in sea surface height (SSH) have long been recognized as a prominent aspect of oceanic variability in the region of 9–13°N in the eastern Pacific Ocean. We use in situ and satellite data to more fully characterize this variability. The oscillations have zonal wavelengths of 550–1650 km and propagate westward in a manner consistent with the dispersion relation for first baroclinic mode, free Rossby waves in the presence of a mean westward flow. Analysis of 9 years of altimetry data shows that the amplitude of the 50- to 100-day SSH variability at 10°N is largest on 90–115°W, with peak amplitudes occurring around April. Some eddies traveling westward at 10–13°N emanate from near the gulfs of Tehuantepec and Papagayo, but eddies sometimes also appear to intensify well away from the coast while in the North Equatorial Current (NEC). The hypothesis that the intraseasonal variability and its annual cycle are associated with baroclinic instability of the NEC is supported by a spatiotemporal correlation between the amplitude of 50- to 100-day variability and the occurrence of westward zonal flows meeting an approximate necessary condition for baroclinic instability. The notion that baroclinic instability may be involved is further corroborated by the tendency of the NEC to weaken while the eddies intensify, even as the wind works to strengthen the current.
    Description: The authors gratefully acknowledge support for the fieldwork under the NOAA Office of Global Programs Pan American Climate Studies program (grants NA66GPO130 and NA96GPO428) and for analysis and publication (grants NA87RJ0445 and NA17RJ1223).
    Repository Name: Woods Hole Open Access Server
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  • 10
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    Magmatic processes in developing oceanic crust revealed in a cumulate xenolith collected at the East Pacific Rise, 9°50′N (2007)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q12O04, doi:10.1029/2006GC001316.
    Description: The petrology and geochemistry of a xenolith, a fragment of a melt-bearing cumulate, within a recently erupted mid-ocean ridge (MOR) lava flow provide information on petrogenetic processes occurring within the newly forming oceanic crust beneath the northern East Pacific Rise (NEPR). The xenolith reveals important petrologic information about MOR magmatic systems concerning (1) melt distribution in a crystal-dominated mush; (2) melt-crystal reactions within the mush; (3) the chemistry of melts that have contributed to the cumulate lithology; and (4) the chemistry of axial melts that enter the axial magma system. The xenolith was enclosed within a moderately primitive, normal mid-ocean ridge basalt (NMORB) erupted in 1991 within the neovolcanic zone of the NEPR, at approximately 9°50′N. The sample is a matrix-dominated, cumulate olivine anorthosite, composed of anorthite (An94-90) and bytownite (An89-70), intergranular olivine (Fo86±0.3), minor sulfide and spinel, and intergranular glass. Marginal corrosion of plagioclase, and possibly olivine, and internal remelting of plagioclase indicate syntexis. It is surmised that the pore volume was eviscerated several times with moderately primitive basaltic melts and reduced by intergranular crystallization of forsteritic olivine. The presence of anorthite as a cumulate phase in the xenolith and the observation of anorthite xenocrysts in NMORB lavas, and as a cumulate phase in ophiolite gabbros, indicate that Ca-rich melts that are not a part of the NMORB lineage play an important role in the construction of the oceanic crust.
    Description: The Mineral Resources Program, USGS, provided support to W.I.R. for this research. Field and laboratory research was supported by NSF grants OCE-9402360, 9403773, and 0138088 to M.R.P. and NSF grants OCE-9819261 and OCE-0525863 to D.J.F.
    Keywords: Ridge ; Xenolith ; Mid-ocean ridge basalt ; Syntexis ; Cumulate ; Crystal mush
    Repository Name: Woods Hole Open Access Server
    Type: Article
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