Disaster diaspora and the consequences of economic displacement and climate disruption,including Hurricanes Matthew (October 8, 2016) and Florence (September 14, 2018) in Robeson County,North Carolina     

Marson  Stephen M.  Legerton  Mac 《Natural Hazards》2021,107(3):2247-2262

Natural Hazards - This paper presents a case study of Robeson County’s challenges in addressing the double-barrel disasters of Hurricane Matthew in 2016 (Category 5) and Hurricane Florence in...  相似文献   

Emplacement temperatures of pyroclastic and volcaniclastic deposits in kimberlite pipes in southern Africa     

Giovanni Fontana  Conall Mac Niocaill  Richard J. Brown  R. Stephen J. Sparks  Matthew Field 《Bulletin of Volcanology》2011,73(8):1063-1083

Palaeomagnetic techniques for estimating the emplacement temperatures of volcanic deposits have been applied to pyroclastic and volcaniclastic deposits in kimberlite pipes in southern Africa. Lithic clasts were sampled from a variety of lithofacies from three pipes for which the internal geology is well constrained (the Cretaceous A/K1 pipe, Orapa Mine, Botswana, and the Cambrian K1 and K2 pipes, Venetia Mine, South Africa). The sampled deposits included massive and layered vent-filling breccias with varying abundances of lithic inclusions, layered crater-filling pyroclastic deposits, talus breccias and volcaniclastic breccias. Basalt lithic clasts in the layered and massive vent-filling pyroclastic deposits in the A/K1 pipe at Orapa were emplaced at >570°C, in the pyroclastic crater-filling deposits at 200–440°C and in crater-filling talus breccias and volcaniclastic breccias at <180°C. The results from the K1 and K2 pipes at Venetia suggest emplacement temperatures for the vent-filling breccias of 260°C to >560°C, although the interpretation of these results is hampered by the presence of Mesozoic magnetic overprints. These temperatures are comparable to the estimated emplacement temperatures of other kimberlite deposits and fall within the proposed stability field for common interstitial matrix mineral assemblages within vent-filling volcaniclastic kimberlites. The temperatures are also comparable to those obtained for pyroclastic deposits in other, silicic, volcanic systems. Because the lithic content of the studied deposits is 10–30%, the initial bulk temperature of the pyroclastic mixture of cold lithic clasts and juvenile kimberlite magma could have been 300–400°C hotter than the palaeomagnetic estimates. Together with the discovery of welded and agglutinated juvenile pyroclasts in some pyroclastic kimberlites, the palaeomagnetic results indicate that there are examples of kimberlites where phreatomagmatism did not play a major role in the generation of the pyroclastic deposits. This study indicates that palaeomagnetic methods can successfully distinguish differences in the emplacement temperatures of different kimberlite facies.  相似文献   

Infiltration in Soils with Fractal Permeability Distribution   总被引：1，自引：0，他引：1  

Marian W. Kemblowski  Ching-Min Chang 《Ground water》1993,31(2):187-192

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Chlorophyll a Biomass of Netplankton in Surface Waters of the Northern North Pacific Ocean and the Adjacent Seas from Summer to Autumn     

Dong-Hoon Han  Masayuki Mac Takahashi 《Journal of Oceanography》2000,56(2):213-222

Chlorophyll a concentrations of net (retained on 30 m mesh net) and total plankton in surface waters were determined along cruise tracks in an area of the northern North Pacific Ocean and the adjacent Bering Sea and the Gulf of Alaska from summer to autumn. Total chlorophyll a concentrations were high with a great areal and temporal variations in the western northern North Pacific compared to the eastern part. Chlorophyll a concentrations of netplankton varied from 0.001 to 0.230 g chl a l^–1 (average, 0.029 ± 0.040 g chl a l^–1), and showed a positive relation but a weak regression coefficient (r ² = 0.551) against the "average total chlorophyll a" (average of total chlorophyll a at the beginning and at the end during sampling of netplankton). However there were several data points showing high "average total chlorophyll a" but low netplankton and vice versa. Average percentage share of netplankton in the total chlorophyll a was estimated to be as large as 4.26%.  相似文献   

Structure and evolution of circumstellar shells formed by massive star winds     

Guillermo García-Segura  Mordecai-Mark Mac Low  Norbert Langer 《Astrophysics and Space Science》1995,224(1-2):459-460

We follow the interaction of massive stars with their circumstellar gas over their entire life-times by combining hydrodynamic stellar evolution calculations for 35 and 60M stars and one- and two-dimensional gas dynamical calculations for the circumstellar medium.  相似文献   

Extreme Nd isotopic variation in the Trinity Ophiolite Complex and the role of melt/rock reactions in the oceanic lithosphere     

G. Gruau  J. Bernard-Griffiths  C. Lécuyer  O. Henin  J. Macé  M. Cannat 《Contributions to Mineralogy and Petrology》1995,121(4):337-350

 Peridotites, dykes and gabbros from the 470–420 Ma Trinity Ophiolite Complex of northern California exhibit large geochemical rare earth element (REE) and Nd isotopic variations on the small scales which are indicative of a complex history. The Trinity Ophiolite, which covers an area of ≈1600 km², consists of three distinct units: (1) a ∼2–4 km-thick sheet of plastically deformed peridotites, including various ultrabasic lithologies (plagioclase and spinel lherzolite, harzburgite, wherlite and dunite); the peridotite unit is a fragment of mantle lithosphere of oceanic affinity; (2) a series of small (∼1 km diameter) undeformed gabbroic massifs; (3) several generations of basic dykes. The peridotites display the largest geochemical and isotopic variations, with ɛ_Nd(T) values ranging from +10 down to 0. In the gabbroic massifs and intrusive dykes, the variation in model ɛ_Nd(T) values is reduced to 7 ɛ_Nd units: 0 to +7. As a general rule, peridotites, gabbros and dykes with ɛ_Nd(T) values around 0 or +3 give less depleted L(light)REE patterns than do those with ɛ_Nd(T) values in the range +7 to +10. In the peridotites, the Nd isotopic variations take place over very short distances, with jumps as large as 7 ɛ_Nd units occurring on scales of less than 20 m. Comparison with available age data indicates that the peridotites with ɛ_Nd(T)≈+10 could be slightly older than the intrusive gabbro massifs and basic dykes (470 Ma vs. 420 Ma). Strontium isotopic data used in connection with Sm-Nd results demonstrate that the 10 ɛ_Nd units variation displayed by the Trinity Peridotite is a primary feature and not an artefact due to REE mobility during seawater interaction. The variable Nd isotopic signatures and variable LREE patterns in the Trinity Peridotite cannot represent mantle source characteristics as there is evidence that this unit was partially melted when it rose as part of the upwelling convecting mantle. Field, petrographic, geochemical and isotopic data rather suggest that the observed heterogeneity is due to local reactions between a 470 Ma proto-peridotite with ɛ_Nd(T)=+10 and younger (420 Ma) basaltic melts with lower ɛ_Nd(T) values (i.e. the gabbroic massifs and the dykes). The gabbros and basic dykes of the Trinity Complex have geochemical and isotopic compositions similar to the arc basalts from the adjacent Copley Formation, so it is proposed that the younger melts are related to arc magmatism. Received: 13 January 1995/Accepted 5 May 1995  相似文献   

Bayesian Decision Analysis for Plume Interception Wells     

Hewa A. Wijedasa  Marian W. Kemblowski 《Ground water》1993,31(6):948-952

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Volcanic history of El Chichón Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity   总被引：1，自引：0，他引：1  

J. M. Espíndola  J. L. Macías  R. I. Tilling  M. F. Sheridan 《Bulletin of Volcanology》2000,62(2):90-104

2 abundance and depletion in MgO, CaO, TiO₂, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization. Received : 4 May 1998 / Accepted: 1 November 1999  相似文献   

Eruption of kimberlite magmas: physical volcanology, geomorphology and age of the youngest kimberlitic volcanoes known on earth (the Upper Pleistocene/Holocene Igwisi Hills volcanoes, Tanzania)     

Richard J. Brown  S. Manya  I. Buisman  G. Fontana  M. Field  C. Mac Niocaill  R. S. J. Sparks  F. M. Stuart 《Bulletin of Volcanology》2012,74(7):1621-1643

The Igwisi Hills volcanoes (IHV), Tanzania, are unique and important in preserving extra-crater lavas and pyroclastic edifices. They provide critical insights into the eruptive behaviour of kimberlite magmas that are not available at other known kimberlite volcanoes. Cosmogenic ³He dating of olivine crystals from IHV lavas and palaeomagnetic analyses indicates that they are Upper Pleistocene to Holocene in age. This makes them the youngest known kimberlite bodies on Earth by >30?Ma and may indicate a new phase of kimberlite volcanism on the Tanzania craton. Geological mapping, Global Positioning System surveying and field investigations reveal that each volcano comprises partially eroded pyroclastic edifices, craters and lavas. The volcanoes stand <40?m above the surrounding ground and are comparable in size to small monogenetic basaltic volcanoes. Pyroclastic cones consist of diffusely layered pyroclastic fall deposits comprising scoriaceous, pelletal and dense juvenile pyroclasts. Pyroclasts are similar to those documented in many ancient kimberlite pipes, indicating overlap in magma fragmentation dynamics between the Igwisi eruptions and other kimberlite eruptions. Characteristics of the pyroclastic cone deposits, including an absence of ballistic clasts and dominantly poorly vesicular scoria lapillistones and lapilli tuffs, indicate relatively weak explosive activity. Lava flow features indicate unexpectedly high viscosities (estimated at >10² to 10⁶?Pa?s) for kimberlite, attributed to degassing and in-vent cooling. Each volcano is inferred to be the result of a small-volume, short-lived (days to weeks) monogenetic eruption. The eruptive processes of each Igwisi volcano were broadly similar and developed through three phases: (1) fallout of lithic-bearing pyroclastic rocks during explosive excavation of craters and conduits; (2) fallout of juvenile lapilli from unsteady eruption columns and the construction of pyroclastic edifices around the vent; and (3) effusion of degassed viscous magma as lava flows. These processes are similar to those observed for other small-volume monogenetic eruptions (e.g. of basaltic magma).  相似文献   

Comparison and Computational Performance of Tsunami-HySEA and MOST Models for LANTEX 2013 Scenario: Impact Assessment on Puerto Rico Coasts     

Jorge Macías  Aurelio Mercado  José Manuel González-Vida  Sergio Ortega  Manuel Jesús Castro 《Pure and Applied Geophysics》2016,173(12):3973-3997

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