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21.
Hetu C. Sheth George Mathew Kanchan Pande Soumen Mallick Balaram Jena 《Journal of Earth System Science》2004,113(4):831-838
Rootless cones, also (erroneously) called pseudocraters, form due to explosions that ensue when a lava flow enters a surface
water body, ice, or wet ground. They do not represent primary vents connected by vertical conduits to a subsurface magma source.
Rootless cones in Iceland are well studied. Cones on Mars, morphologically very similar to Icelandic rootless cones, have
also been suggested to be rootless cones formed by explosive interaction between surface lava flows and ground ice. We report
here a group of gentle cones containing nearly circular craters from Mount Pavagadh, Deccan volcanic province, and suggest
that they are rootless cones. They are very similar morphologically to the rootless cones of the type locality of Myvatn in
northeastern Iceland. A group of three phreatomagmatic craters was reported in 1998 from near Jabalpur in the northeastern
Deccan, and these were suggested to be eroded cinder cones. A recent geophysical study of the Jabalpur craters does not support
the possibility that they are located over volcanic vents. They could also be rootless cones. Many more probably exist in
the Deccan, and volcanological studies of the Deccan are clearly of value in understanding planetary basaltic volcanism. 相似文献
22.
The seasonality of carbon dioxide partial pressure(pCO_2).air-sea CO_2 fluxes and associated environmental parameters were investigated in the Antarctic coastal waters.The in-situ survey was carried out from the austral summer till the onset of winter[January 2012,February 2010 and March 2009) in the Enderby Basin.Rapid decrease in pCO_2 was evident under the sea-ice cover in January,when both water column and sea-ice algal activity resulted in the removal of nutrients and dissolved inorganic carbon(DIC) and increase in pH.The major highlight of this study is the shift in the dominant biogeochemical factors from summer to early winter.Nutrient limitation(low Si/N),sea-ice cover,low photosynthetically active radiation(PAR),deep mixed layer and high upwelling velocity contributed towards higher pCO_2during March(early winter).CO_2 fluxes suggest that the Enderby Basin acts as a strong CO_2 sink during January(-81 mmol m~2 d~(-1)),however it acts as a weak sink of CO_2 with-2.4 and-1.7 mmol m~(-2) d~(-1)during February and March,respectively.The present work,concludes that sea ice plays a dual role towards climate change,by decreasing sea surface PCO_2 in summer and enhancing in early winter.Our observations emphasize the need to address seasonal sea-ice driven CO_2 flux dynamics in assessing Antarctic contributions to the global oceanic CO_2 budget. 相似文献
23.
A depth-averaged numerical model has been developed to study tidal circulation and suspended sediment transport in the Gulf of Kachchh including Kandla creek, west coast of India. The resolution of the model is taken as 750 m × 750 m, which is found to be adequate for the gulf region. However, this resolution could not produce the realistic circulation pattern and suspended sediment concentration in the Kandla creek region. There is a major seaport at Kandla which serves as the sea gate to northwest India. Therefore, a 2-D fine resolution (75 m × 75 m) model for Kandla creek has been developed and coupled with the coarser gulf model to compute the flow features in the creek region. The model dynamics and basic formulation remain the same for both the gulf model and the creek model. The models are barotropic, based on shallow water equations, and neglect horizontal diffusion and wind stress terms in the momentum equations. The models are fully nonlinear and use a semiexplicit finite difference scheme to solve mass, momentum, and advection-diffusion equations in a horizontal plane. The tide in the gulf is represented in the model by the semidiurnal M2 constituent mainly. In this study, no fresh water discharge conditions have been considered so the results are appropriate for the dry season. Numerical experiments are carried out to study the circulation and suspended sediment concentrations in the gulf and the creek regions. The computed results are validated with the available observations. 相似文献