Fine-scale analysis of shelf–slope physiography across the western continental margin of India

We attempt here to quantify and model physiographic features off the central west coast of India in terms of power spectral exponent, amplitude parameter. We demonstrate that statistical analysis of multi-beam echo-sounder grid bathymetry data is able to characterise the outer shelf, upper slope, shelf margin basin and several structural rises in the region. A scatter diagram analysis shows that the seafloor data can be grouped into two distinct clusters. Distinctly different clustering patterns are observed over the structural rises, compared to the shelf, slope and basinal areas. This suggests different modes of formation for the members of these two clusters. In fact, the steep structural rises appear to be part of the NW–SE-trending coast-parallel Mid-Shelf Basement and Prathap ridges. These ridges are rift-induced volcanic emplacements on a stretched and thinned continental crust which probably formed during mid-Cretaceous times.     

Analysis of multibeam-Hydrosweep echo peaks for seabed characterisation

Echo-peak data of outer and normal incidence beams from five different Southern Ocean bottom topographic regions have been analysed. The Rice and Extremal probability density function (PDF) statistical approaches reveal that the seabed roughness is, in general, Gaussian in nature except in the case of the Kainan Maru seamount summit (area D). The outer beams of the Enderby abyssal plain (area C) echo-peak PDF statistics reveal the highest possible large-scale feature dominance. Interestingly, Extremal PDF fit parameters (!) from the Agulhas Basin (area A) show a less dominant large-scale roughness than in the case of area C. Large-scale feature dominance up to 15° beam angle is observed in the case of mixed roughness seabeds such as area B (southwest Indian ridge) and area E (Meteor Rise). No increase in the 30°-beam Extremal PDF parameters is observed in these areas. Maximum microtopographic roughness is documented in area D on the summit of Kainan Maru seamount. The estimated fit parameters using Extremal statistics of outer-beam peak data provide a better understanding of the scattering process. Previously determined power law and volume roughness parameters using composite roughness theory are given for the five different areas. These support the results obtained using Rice and Extremal PDFs. The existence of higher volume roughness parameters and power law parameters for medium-scale roughness, along with dominant microtopographic features, are evident from the results of this study.     

Assessment and monitoring of urbanisation on Himalayan lacustrine environment-a case study in Mirik municipality area

The Mirik lake is a well-known tourist destination in the Darjeeling Himalayan region of West Bengal. In the last few decades, the lake area experienced a surge in demand for the hospitality industry with the consequences of unrestricted municipal town growth. On this perspective, this research work addresses the contemporary problems of the Mirk municipality area involving the lake system using technologies of remote sensing and GIS. In accordance with the primary objective, the detailed land use/land cover change analysis of the past twenty years shows a significant escalating trend in built-up area as it has increased from 149.85 ha in 2000 to 178.25 ha in 2020, where the lake expresses a steady reduction of its perennial part. The gradual shrinkage in the lake area may become of grave concern and therefore, this particular work tries to examine the water quality parameters of Mirik lake. Analyses have shown that the lake shrinkage may be attributed to waste disposal, landfill pollution etc., substantially contributed to the raised level of suspended sediment concentration (3724.26 mg/lit in 2020) near the boundaries. Moreover, the outcome of the developed water pollution model identifies that the western and south-western parts of the lake are the most polluted regions and confirms numerous inlets of the western side push up the level of phosphorus, nitrogen and biological oxygen demand in lake water. Such lake degradation is a real threat to the mountainous lacustrine environment, and it requires comprehensive plans for better management practices at some regular interregnum.

     

Implications of urban expansion on land use and land cover: towards sustainable development of Mega Manila,Philippines

GeoJournal - Planning of land use and infrastructure in advance for a population that is projected to grow rapidly is highly important for its sustainable development. A correlative approach of...     

Rock mass damage from underground blasting, a literature review, and lab- and full scale tests to estimate crack depth by ultrasonic method

Rock mass damage due to blasting (BID) is important for the personnel working underground and also for rock reinforcement costs. Therefore, about 20 methods for damage assessment have been developed. The methods are shortly presented. Often several methods have to be used in combination to achieve good quantitative estimate of the damage. Some blast damage indices have been developed and one of them, the D_ib (Yu & Vongpaisal 1996) after a modification of the Index was tested in field with good result. The ultrasonic method used both in lab and field tests has limited value and can only used with good accuracy to a depth of ~0.5 m. This method is not therefore recommended for blast damage measurements where damage depth could be up to 2.5 m.     

Spacetime dynamics of bed forms due to turbulence around submerged bridge piers

Stochastic Environmental Research and Risk Assessment - This work presents a study of spatiotemporal changes of scour-holes around sand embedded submerged circular and non-circular cylinders with...     

Effect of nonthermality on the perturbation dynamics of self-gravitating complex fluids

The perturbation dynamics of an unbounded nonthermal self-gravitating inhomogeneous viscoelastic system composed of two-component constitutive fluids is theoretically investigated. The role of fluid turbulence, which is a highly nonlinear hydrodynamic vorticity-driven phenomenology, is included via the Larson logatropic equation of state describing nonlinear fluid pressure effects. The thermodynamics of the variable-temperature bulk fluid is included with the help of a proper heat diffusion equation. The system is coupled by the electro-gravitational Poisson equations in a closed form. A generalized linear dispersion relation (cubic in degree) is procedurally obtained using a standard technique of linear normal mode analysis. The dispersion relation stems from the rudimentary condition of non-vanishing perturbed gravitational potential in a linear order. The propagatory and dispersive features of the composite fluid perturbations are numerically explored with a special attention to the nonthermality effects. Their growth characteristics are analyzed alongside promising indication to applicability in the astro-cosmo-plasmic context.     

Supernova neutrinos: Flavor conversion independent of their mass

In extremely dense neutrino environments like in supernova core, the neutrino-neutrino refraction may give rise to self-induced flavor conversion. These neutrino flavor oscillations are well understood from the idea of the exponentially growing modes of the interacting oscillators in the flavor space. Until recently, the growth rates of these modes were found to be of the order of the vacuum oscillation frequency \(\Delta m^2/2E\) [\(\mathcal {O}(1~\mathrm{km}^{-1})\)] and were considered slow growing. However, in the last couple of years it was found that if the system was allowed to have different zenith-angle distributions for the emitted \(\nu _e\) and \(\bar{\nu }_e\) beams then the fastest growing modes of the interacting oscillators grew at the order of \(\mu =\sqrt{2} G_\mathrm{F}n_{\nu }\), a typical \(\nu \)–\(\nu \) interaction energy [\(\mathcal {O}(10^5~\mathrm{km}^{-1})\)]. Thus the growth rates are very large in comparison to the so-called ‘slow oscillations’ and can result in neutrino flavor conversion on a much faster scale. In fact, the point that the growth rates are no longer dependent on the vacuum oscillation frequency \(\Delta m^2/2E\), makes these ‘fast flavor conversions’ independent of \(\Delta m^2\) (thus mass) and energy. This is a surprising result as neutrino flavor conversions are considered to be the ultimate proof of massive neutrinos. However, the importance of this effect in the realistic astrophysical scenarios still remains to be understood.     

Petrography,classification, oxygen isotopes,noble gases,and cosmogenic records of Kamargaon (L6) meteorite: The latest fall in India

A single piece of meteorite fell on Kamargaon village in the state of Assam in India on November 13, 2015. Based on mineralogical, chemical, and oxygen isotope data, Kamargaon is classified as an L‐chondrite. Homogeneous olivine (Fa: 25 ± 0.7) and low‐Ca pyroxene (Fs: 21 ± 0.4) compositions with percent mean deviation of <2, further suggest that Kamargaon is a coarsely equilibrated, petrologic type 6 chondrite. Kamargaon is thermally metamorphosed with an estimated peak metamorphic temperature of ~800 °C as determined by two‐pyroxene thermometry. Shock metamorphism studies suggest that this meteorite include portions of different shock stages, e.g., S3 and S4 (Stöffler et al. 1991 ); however, local presence of quenched metal‐sulfide melt within shock veins/pockets suggest disequilibrium melting and relatively higher shock stage of up to S5 (Bennett and McSween 1996 ). Based on noble gas isotopes, the cosmic‐ray exposure age is estimated as 7.03 ± 1.60 Ma and nitrogen isotope composition (δ¹⁵N = 18‰) also correspond well with the L‐chondrite group. The He‐U, Th, and K‐Ar yield younger ages (170 ± 25 Ma 684 ± 93, respectively) and are discordant. A loss of He during the resetting event is implied by the lower He‐U and Th age. Elemental ratios of trapped Ar, Kr, and Xe can be explained through the presence of a normal Q noble gas component. Relatively low activity of ²⁶Al (39 dpm/kg) and the absence of ⁶⁰Co activity suggest a likely low shielding depth and envisage a small preatmospheric size of the meteoroid (<10 cm in radius). The Kr isotopic ratios (⁸²Kr/⁸⁴Kr) further argue that the meteorite was derived from a shallow depth.