17-Feb-2022: Unraveling tectonic evolution of Greater Maldive Ridge in western Indian Ocean can reconstruct Gondwanaland break up & dispersal

In a recent study, an Indian researcher traced the tectonic evolution and the nature of the Greater Maldive Ridge (GMR) --- a very crucial geodynamic features in the western Indian Ocean whose origin has been the centre of many a scientific debate.

The study can help reconstruct the original Gondwanaland break up and dispersal that led to present-day configuration of continents, continental fragments, and formation of ocean basins in the Indian Ocean.

The Maldive Ridge is an aseismic ridge that is not associated with earthquake activities. This ridge, located in the western Indian Ocean, southwest of India, is not well investigated. It is of paramount importance to gain knowledge on the structure and geodynamics of aseismic ridges (as it provides valuable inputs towards understanding the evolution of ocean basins).

The study by the Indian Institute of Geomagnetism, Mumbai, an autonomous institute of the Department of Science & Technology, Govt. of India, has chalked the possible geological cross-sections along the GMR for the first time with the help of satellite-derived high-resolution gravity data. The researchers postulated that the GMR may be underlain by an oceanic crust. The results from their study can provide additional constraints in understanding the plate-tectonic evolution of the Indian Ocean, better.

The research work carried out by Dr. Priyesh Kunnummal under the guidance of Dr. S.P. Anand provides the crustal architecture and the state of gravitational equilibrium between Earth's crust and mantle (isostasy) of the Greater Maldive Ridge segment of the larger Chagos-Laccadive Ridge (CLR) system. Their study, based mainly on the interpretation of gravity anomalies (small differences in the pull of gravity caused by the lateral variations of density within the subsurface) with broadband seismic and refraction seismic data, provided for the first time a three-dimensional picture of the variation of Moho along the Greater Maldive Ridge and the adjoining ocean basins. The depth to the boundary between the earth’s crust and the mantle or the Mohorovicic discontinuity (Moho) over the GMR was systematically mapped along with the finer variation of effective elastic thickness (Te) at the place. The research related to Te variations and isostatic compensation has been published recently in the journal ‘Gondwana Research’.

IIG team found that Moho is deeper over the Maldive Ridge (MR) segment and shallows southwards in the Deep Sea Channel region (DSC). However, the effective elastic thickness (a proxy for the strength of the lithosphere) values were lower over the MR compared to DSC region. Maldive Ridge and Deep Sea Channel region may probably be oceanic in nature with the presence of underplated materials associated with the Reunion hotspot volcanism. The research suggests that Maldive Ridge might have formed in the close vicinity of the Mid-Oceanic Ridge (where creation of a new ocean floor occurs due to divergent motion of lithospheric plates or spreading centre). Meanwhile, the DSC region was under a long transform fault (offset between the spreading centres, which neither create nor destroy lithosphere), which hindered melt production and gave rise to gap between Chagos and Maldive Ridge during the Plume-ridge interaction.

Satellite-derived gravity anomalies are very helpful in deciphering the crustal architecture where traditional shipborne geophysical data are either not available or scanty.

“The study provides new insights into the crustal architecture, isostatic compensation mechanism, and the tectonic evolution of the Greater Maldive Ridge, said Dr. Priyesh.

10-Feb-2022: New study suggests increase in warming in high altitude Himalayas due to water vapor

A recent study has shown that water vapour exhibits a positive radiative effect at the top of the atmosphere (TOA), suggesting an increase in overall warming in the High Altitude Himalayas due to it.

The precipitable water vapor (PWV) is one of the most rapidly varying components in the atmosphere and is mainly accumulated in the lower troposphere. Due to the large variability in space and time, mixing processes and contribution to a series of heterogeneous chemical reactions, as well as sparse measurement networks, especially in the Himalayan region, it is difficult to accurately quantify the climatic impact of PWV over space and time. Moreover, aerosol-cloud-precipitation interactions over this region, which are one of the most climatic-sensitive regions, are poorly understood, apparently due to a lack of proper observational data.

The recent research led by Dr Umesh Chandra Dumka from Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, an autonomous research institute of the Department of Science and Technology (DST) Govt. of India, showed that Precipitable Water Vapour (PWV) exhibits a positive radiative effect at the top of the atmosphere (TOA) in high altitude remote locations in the order of about 10 watts per square metre (W m-2) at Nainital (Altitude -2200m; Central Himalaya) and 7.4 W m-2 at Hanle (Altitude -4500m; western Trans Himalaya).

Team members from the National Observatory of Athens (NOA), Greece; Tohoku University, Japan; Indian Institute of Astrophysics (IIA) and CSIR Fourth Paradigm Institute (CSIR-4PI), Bengaluru and Institute for Advanced Sustainability Studies, Germany also contributed in the study. The research published in the Journal of Atmospheric Pollution Research, Elsevier shows that the atmospheric radiative effect due to PWV is about 3-4 times higher compared to aerosols, resulting in atmospheric heating rates of 0.94 and 0.96 K Day-1 at Nainital and Hanle, respectively. The results highlight the importance of PWV and aerosol radiative effects in the climate-sensitive Himalayan region.

The researchers assessed the combination of aerosols and water vapour radiative effects over the Himalayan range that is specifically important for regional climate and highlighted the importance of water vapour as a key greenhouse gas and climate forcing agent over the Himalayan region.

The team believes that this work will provide a comprehensive investigation of the combined impact of aerosols and water vapour on the radiation budget.

15-Dec-2021: Research on Himalayan Geology

Scientists of Wadia Institute of Himalayan Geology, while studying the glaciers in the upper Kali Ganga valley, Pithoragarh district of Uttarakhand, Himalaya, found that the 5 km long unnamed glacier (30.28089N- 80.69344E), covering an area of ~ 4 km2 in Kuthi Yankti valley (Tributary of Kali River), abruptly changed its main course and merged with an adjacent glacier named Sumzurkchanki, due to changes in climate and tectonic forcing sometime between the Last Glacial Maxima (19-24,000 years ago) and Holocene (10,000 years ago).

The Government encourages further research and study on the Himalayan region to find solutions to frequent natural calamities.

The government encourages research on the natural calamities in the Himalayan region by numerous research institutes, universities, IITs, IISc, etc. Ministry of Earth Sciences (MoES) through its National Centre for Seismology is involved in the research using the recorded earthquake data to understand various phenomena related to earthquake processes and seismic hazard assessment particularly for Himalayan region. The Wadia Institute of Himalayan Geology has been pursuing research in understanding the causes and consequences of earthquakes, landslides and avalanches in the Himalaya with a view to provide mitigation measures.