Geology

A fter learning about how the earth was born, how it evolved its crust and other inner layers, how its crustal plates moved and are moving, and other information on earthquakes, the forms of volcanism and about the rocks and minerals the crust is composed of, it is time to know in detail about the surface of the earth on which we live. Let us start with this question. Why is the surface of the earth uneven? First of all, the earth's crust is dynamic. You are well aware that it has moved and moves vertically and horizontally. Of course, it moved a bit faster in the past than the rate at which it is moving now. The differences in the internal forces operating from within the earth which built up the crust have been responsible for the variations in the outer surface of the crust. The earth's surface is being continuously subjected to external forces induced basically by energy (sunlight). Of course, the internal forces are still active though with different intensities. That means, the earth's surface is being continuously subjected to by external forces originating within the earth's atmosphere and by internal forces from within the earth. The external forces are known as exogenic forces and the internal forces are known as endogenic forces. The actions of exogenic forces result in wearing down (degradation) of relief/elevations and filling up (aggradation) of basins/depressions, on the earth's surface. The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation. The endogenic forces continuously elevate or build up parts of the earth's surface and hence the exogenic processes fail to even out the relief variations of the surface of the earth. So, variations remain as long as the opposing actions of exogenic and endogenic forces continue. In general terms, the endogenic forces are mainly land building forces and the exogenic processes are mainly land wearing forces. The surface of the earth is sensitive. Humans depend on it for their sustenance and have been using it extensively and intensively. So, it is essential to understand its nature in order to use it effectively without disturbing its balance and diminishing its potential for the future. Almost all organisms contribute to sustain the earth's environment. However, humans have caused over use of resources. Use we must, but must also leave it potential enough to sustain life through the future. Most of the surface of the earth had and has been shaped over very long periods of time (hundreds and thousands of years) and because of its use and misuse by humans its potential is being diminished at a fast rate. If the processes which shaped and are shaping the surface of the earth into varieties of forms (shapes) and the nature of materials of which it is composed of, are understood, precautions can be taken to minimise the detrimental effects of human use and to preserve it for posterity.

Water quality degradation exerts immense pressure on the availability of suitable freshwater resources. Deterioration in water quality has led to a decrease in the available water for consumption purposes. The excess concentration of heavy metals and faecal contamination in water pose a risk to human health. This study looks at heavy metal contamination and microbial contamination in different water samples of the east and south districts of Sikkim. The sampling extended for tap water, springs, and river water samples across monsoon, post-monsoon, and pre-monsoon seasons. The concentrations of heavy metals in most samples, except for some river water samples were under permissible limits set by the Bureau of Indian Standards (BIS) and World Health Organisation (WHO). Indices such as Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), and Contamination Index (C d) show a higher proportion of contamination in the river water samples than in tap and spring water samples and during monsoon season. Sources apportionment of metal concentration show geogenic as well as anthropological sources. For microbial contamination Most Probable Number (MPN) index was used showing possible faecal contamination in all water samples rendering them unsuitable for drinking purposes without appropriate treatment. The study also highlights the urgent need for effective measures to address faecal contamination in the water sources of the study area.

Black carbon (BC) and brown carbon (BrC) have versatile nature, and they have apparent role 13 in the climate variability and changes. As the anthropogenic activity is surging, the BC and 14 BrC are also reportedly increasing. So, the monitoring of BC/BrC and observation of land use 15 land cover changes (LULCC) at regional level are necessary for the various interconnected 16 meteorological phenomenal changes. The current study investigates BC, BrC, CO2, BC from 17 fossil fuels (BCff), BC from biomass burning (BCbb), LULCC, and their relationship to the 18 corresponding meteorological conditions over Gangtok in Sikkim Himalayan region. The 19 concentration of BC (BrC) 43.5 μg/m 3 (32.0 μg/m 3) is found to be highest during the March-20 2022 (April-2021). Surface pressure has been found to have a significant positive correlation 21 with BC, BCff, BCbb and BrC. The boundary layer is calmer and more stable when the surface 22 pressure is higher, which keeps contaminants deposited there. The wind, on the other hand, 23 appears to represent the dispersion of pollutants with a strong negative correlation. The fact 24 that all pollutants and precipitation have been shown to behave similarly points to moist 25 scavenging of the pollutants. Despite the dense cloud cover, it is clear that the area is not 26 receiving convective precipitation, implying that orographic precipitation is occurring over the 27 region. Most of Sikkim receives convective rain from May to September, indicating that the 28 region has significant convective activity contributed from the Bay of Bengal during monsoon 29 season. Furthermore, monsoon months have the lowest concentrations of BC, BCbb, BCff, and 30 BrC, suggesting the potential of convective rain (as rain out scavenging) to remove most of 31 the pollutants. Moreover, BC and BrC show positive radiative feedback.