The extinction of the mammoths

Two kinds of blanket of fine grains in the Earth's upper atmosphere are possible: a blanket of reflective dielectric particles and one of absorbing metallic particles. The first is a trigger for the onset of an ice-age, and the second a trigger for the disappearance of an ice-age. The facts support the view that it was a blanket of absorptive particles which caused the extinction of the mammoths.     

A unified presentation of the Voigt functions

This paper aims at presenting a unified study of the Voigt functionsK(x,y) andL(x,y) which play a rather important role in several diverse fields of physics such as astrophysical spectroscopy and the theory of neutron reactions. Explicit expressions for these functions are given in terms of relatively more familiar special functions of one and two variables; indeed, each of these representations will naturally lead to various other needed properties of the Voigt functions.     

Modeling Vulnerability and Resilience to Climate Change: A Case Study of India and Indian States

The vulnerability of India and Indian states to climate change was assessed using the Vulnerability-Resilience Indicator Prototype (VRIP). The model was adapted from the global/country version to account for Indian dietary practices and data availability with regard to freshwater resources. Results (scaled to world values) show nine Indian states to be moderately resilient to climate change, principally because of low sulfur emissions and a relatively large percentage of unmanaged land. Six states are more vulnerable than India as a whole, attributable largely to sensitivity to sea storm surges. Analyses of results at the state level (Orissa, and comparisons between Maharashtra and Kerala, and Andhra Pradesh and Himachal Pradesh) demonstrate the value of VRIP analyses used in conjunction with other socio-economic information to address initial questions about the sources of vulnerability in particular places. The modeling framework allows analysts and stakeholders to systematically evaluate individual and sets of indicators and to indicate where the likely vulnerabilities are in the area being assessed.     

A reconstruction of the northeastern pacific from the hawaiian-emperor hotspot trace

The evolutionary history of the Pacific Ocean is reconstructed back to 60 m.y. B.P. based on the Hawaiian Island chain and Emperor seamounts, which join at an elbow to form the Hawaiian hotspot trace on the Pacific plate. This trace can be interpreted as a series of two rotations of the Pacific plate about the Hawaiian hotspot, presently located beneath Hawaii. Utilizing a pair of rotation poles in accordance with previously proposed models, the evolution can be described by the following:

1. (1) a rotation of 0.8°/m.y. about the Emperor pole of 17°N and 107°W from 60 to 42 m.y. B.P., and

2. (2) a rotation of 0.89°/m.y. about the Hawaiian pole of 69°N and 68°W from 42 m.y. B.P. to present.

This model fits several constraints:

1. (1) the hotspot trace must continually pass through the hotspot,

2. (2) the elbow must reach the hotspot at 42 m.y. B.P,

3. (3) transform faults must lie on observed fracture zones,

4. (4) the first contact between the North American and Pacific plates must occur at about 30 m.y. B.P., and

5. (5) the motion between the North American and Pacific plates has been right-lateral from 30 m.y. B.P. to present.

The overall fit of the digitized data of the hotspot trace to this model shows that it is possible to use the given poles for finite rotations and that the Kula-Pacific ridge is just now subducting.     

The Santa Filomena meteorite shower: Trajectory,classification, and opaque phases as indicators of metamorphic conditions

On August 19, 2020, at 13:18—UTC, a meteor event ended as a meteorite shower in Santa Filomena, a city in the Pernambuco State, northeast Brazil. The heliocentric orbital parameters resulting from images by cameras of the weather broadcasting system were semimajor axis a = 2.1 ± 0.1 au, eccentricity e = 0.55 ± 0.03, and inclination i = 0.15^o ± 0.05. The data identified the body as an Apollo object, an Earth-crossing object with a pericenter interior to the Earth's orbit. The chemical, mineralogical, and petrological evaluations, as well as the physical analysis, followed several traditional techniques. The meteorite was identified as a H5-6 S4 W0 ordinary chondrite genomict breccia. The large amount of metal in the meteorite made a metallographic evaluation based on the opaque phases possible. The monocrystalline kamacite crystals suggest a higher petrological type and the distorted Neumann lines imply at least two different shock events. The absence of the plessite phase shows that the meteorite did not reach the highest shock levels S5 and S6. The well-defined polycrystalline taenite is indicative of petrologic types 4 and 5 due to the conserved internal tetrataenite rim at the boundaries. The presence of polycrystalline taenites and the characteristics of the Agrell Effect suggest that the Santa Filomena meteorite did not reheat above 700°C. The absence of martensite confirms reheating temperatures <800°C and a slow cooling rate. The Ni contents and sizes of the zoned taenite particles indicate a slow cooling rate ranging from 1 to 10 K Myr⁻¹.     

An alternative approach to reveal critical behaviour in the case of the Mw 6.3 Aquila earthquake

An independent approach, based on a power law relation interconnecting the lead time of precursory signals and the stress drop of forthcoming earthquake, confirms the reported evidence that the observed magnetic field anomaly and consequently, according to Maxwell’s laws, electric field anomaly prior to Mw 6.3 Aquila earthquake in 2009 exhibit features of criticality. Precisely, by inserting the data from Aquila earthquake in this power law, we get an exponent α = 0.329, which is in excellent agreement with previously found ones and falls within the range values (0.3–0.4) for critical exponents for fracture. This fact implies that upon the initiation of the observed magnetic field anomaly and the associated electric signal prior to Aquila earthquake, the prefocal area enters into a critical stage where nonlinear dynamic processes, typical behaviour of a system close to criticality, prevail.     

Metal accumulation by plant species growing on a mine contaminated site in Mexico

The present work aims to assess the efficiency of heavy metal accumulation of native species growing in contaminated soils in the mining district of Taxco, Mexico. Soil and tailing sampling was conducted in three study sites: La Concha, El Fraile, and a control site. The study localities present diverse metal concentrations with significant differences in their proportion in the geochemical fractions. Results show that species Cupressus lindleyi and Juniperus deppeana accumulate Zn and Mn in anomalous concentrations at La Concha, where Zn is present in soluble fractions. Manganese, despite not being present mostly in the soluble fraction in soils and tailings, seems to have been increased in the soluble fraction after the plant growth. In contrast, samples of the same species taken at El Fraile and in the control site, where Zn and Mn are mainly contained in the residual fraction, do not show an anomalous enrichment. Other analyzed species growing under the same contamination conditions in La Concha (Jacaranda mimosifolia and Psidium guajava) do not show anomalous concentrations. These facts confirm the Zn and Mn accumulation capacity of C. lindleyi and Ju. deppeana, which depends on their accumulation ability and on the concentration of these elements in the soluble fraction.     

P-T conditions of earliest Late Cretaceous metamorphism in the Western Sonobari Complex,northwestern Mexico: tectonic implications

The Western Sonobari Complex in northwestern Mexico consists of metamorphosed rocks mostly derived from Palaeozoic (?) sedimentary and Mesozoic igneous protoliths. Rocks of this complex display amphibolite facies orogenic metamorphism, pervasive foliation, migmatization, and four folding phases. These features are ascribed to a contractional tectonic event with NNW–SSE shortening direction, which caused thrusting, thickening of the crust, and sinking of the lithological units. U–Pb geochronology of migmatitic leucosome bands indicates that peak metamorphic conditions were reached between ~93 and 89 Ma. Post-tectonic Late Cretaceous peraluminous aplite-pegmatite dikes transect the metamorphic foliation. Traditional thermobarometry in the metamorphic rocks yields average pressures and temperatures of 9.0–7.1 kbar and 745–663°C, typical of intermediate P/T Barrovian metamorphism. On the basis of its age and contractional character, the thickening event originating the metamorphism may be related to collision of the Alisitos island arc against crustal blocks of Mexico. Thermobarometric data of post-tectonic intrusives including Late Cretaceous granodiorite and Eocene gabbro indicate emplacement within an overthickened crust, while P-T conditions of post-tectonic dikes point towards an almost isothermal decompression path along the amphibolite facies field. Rock units of similar age and metamorphic character are discontinuously exposed from the Islas Marias offshore the Nayarit coast to the Peninsular Ranges batholith of Baja California, and even extend north into the Sierra Nevada batholith and the Sevier hinterland. This extensive belt of Barrovian metamorphic rocks thus provides a record of middle Cretaceous shortening and crustal thickening related to arc-continent collision followed by subduction resuming.