India India- the world's largest democracy, is comprised of a total of 29 states along with seven union territories and is the second most populated country in the world. Spread over an area of 3,287,263 sq km, our country shares international borders with seven countries, namely Pakistan, China, Afghanistan, Myanmar, Bhutan, Nepal and Bangladesh. Our’s is a big tropical country experiencing variety of climates ranging from tropical in the south to temperate and alpine in the Himalayan north. The Himalayas work as a barrier to the Westerly winds, which blow down from Central Asia. The Tropic of Cancer passes through the middle of the country and this makes its climate more tropical. Physiographic regions in the country: The Himalayan Mountain Range The Indian Peninsula The Indo Gangetic Plains The Great Indian Thar Desert The Western and Eastern Ghat Mountain Ranges The coastline measuring 7,517 kilometres in length, out of which a distance of 5,423 kilometres belongs to the peninsular India and 2,094 kilometres belongs to Andaman, Nicobar and Lakshadweep island chains. Additionally, along with mainland coastline include 43% sandy beaches, 46% mudflats/marshy shores and 11% rocky shores. Water bodies that surround our country from different sides: Lakshadweep Sea in the southwest Arabian Sea in the west Bay of Bengal in the east Indian Ocean in the south Our country houses 12 rivers that are categorized as important rivers and several smaller ones. The overall drainage basin watered by these rivers is more than 976,000 sq miles or 2,528,000 km2. All the important rivers in the country have their sources in any of the following areas: Vindhya and Satpura mountain range, forming a part of the heart of the country The Karakoram and Himalayan mountain ranges Western Ghats mountain range, forming a part of western India The biggest drainage basin in the country is created by the Ganges-Brahmaputra-Meghana river network and it covers a total area of approximately 620,000 sq miles or 1,600,000 km2. The drainage basin of the Ganges river singularly covers a total area of around 420,000 sq miles or 1,100,000 km2. The major lakes in India are as follows - Vembanad Lake (Kerala), Sambhar Lake, (the biggest saltwater lagoon of the nation in Rajasthan), Loktak Lake (Manipur), Kolleru Lake (Andhra Pradesh), Chilka Lake (Orissa), Dal Lake (Jammu & Kashmir), Pangong Tso, Tso Moriri and Tso kar (Ladakh, Jammu & Kashmir), Sasthamkotta Lake (Kerala). Salient Features in Quaternary Research India has come a long way in Quatenary researches. Some of them are listed - The 2500-km long Himalayan Ranges have over 15000 glaciers. Late Quaternary is characterized by various degrees of asynchronous glacial behaviour. At least five glacial events have been identified in Western Himalaya since LGM. Prevalence of C3 species-dominated moist semi-evergreen forest in East Himalaya until the LastGlacial Maxima (LGM). The Early Holocene (_9.5 ka) in the Higher Himalaya was characterized by incision of the valley fills induced by high fluvial discharge associated with intensified monsoon as recorded in the Alaknanda Valley. Tree-ring width chronologies longer than 1000 years have been produced in the Himalaya reconstructing humidity conditions. Chronologies of >500 year long from the peninsular region confer information regarding temperature variations. Large floods on the Himalayan rivers during the Holocene have generally occurred during early Holocene Climatic Optimum and the Medieval Climate Anomaly. In general, most extreme floods on the these rivers are a result of failure of landslide and glacially dammed lakes. The presence of Mega lake systems in the Trans and Tethyan Himalaya during the Late Quaternary. Ionic load of Indus water largely from the silicate rocks, while the other smaller rivers show a mix of contribution from silicate and carbonate sources. Millennial–orbital scale variations in the Indian summer monsoon and monsoon variability driven directly related to Northern Hemisphere summer insolation is indicated by speleothem oxygen isotope record from Uttarakhand. Lake records across the Indian subcontinent show an intensified monsoon between 9 and 5 ka,corresponding with the globally recorded warm and wet Holocene Climate Optimum. A generaltrend in aridity is recorded throughout India after about 4 ka also support these findings. Records based on drill cores from the Ganga Valley reveal a general weakening of Indian monsoon during the transition period from late MIS-5 to 4 and renewed fluvial activity in the post-LGM period followed by incision as well as southward migration of the Ganga River after 6 ka. Palaeo-ethnobotanical finds from Chalcolithic site reveal advanced agricultural practices in Upper Ganga Plain; domestication of plants, early farming and ecosystem dynamics during Holocene/ Anthropocene and 7 ka old rice chronologies of archaeological significance. Studies of palaeosols in the Ganga-Yamuna interfluve reveal three major phases of humid conditions spanning 90-80 ka, 50-30 ka and 10 ka with intervening drier phases. In the Thar Desert, the Indian monsoon maxima during MIS-4 is represented by aeolian sand deposition (75 and 55 ka) due to strengthened monsoonal winds. Aeolian activity and dune building in the Thar Desert during early Holocene continued until ~6.8 ka, at ~5 ka and ~3.5 ka coinciding with drier periods. Records of palaeofloods from Peninsular India suggest that exceptionally high floods occurred during Medieval Warming Period and post-1950 CE, whereas the Little Ice Age (LIA) was characterized by lower magnitude floods. Multiple studies also indicate distinct flood clusters during the times of major shifts in the monsoon climate in western and southern Indian rivers. The vertical uplift rates along the major active faults range from 0.8 to 2.8 mm/yr in the Kachchh region, western India. West Coast has experienced marginally higher sea stand during 6 ka to 3 ka period. A high-resolution speleothem oxygen isotope record from Mawmluh Cave, located over the Meghalaya Plateau in Northeast India, has provided evidence of an abrupt decline in monsoon rainfall at ~4.2 ka. This distinct event was the prime candidate to formally ratify the post ~4.2 ka period as the Meghalayan Age. The Indian region is rich in Acheulian, Middle Palaeolithic, Microlithic, Neolithic and Chalcolithic sites. Cosmogenic nuclide dating of Acheulian artefacts from southern Peninsular India indicate that during the Early Pleistocene (ca 1.5 Ma), India was already occupied by hominins fully conversant with an Acheulian technology. Further, the early Middle Palaeolithic culture in India has now been firmly dated to around 385–172 ka. Fossil mangrove deposits show that Holocene sea rose from below -12.8 to 1.2 m above present level between 8 and 6 ka and between 5 and 4 ka. The sea transgressed in East Coast of India intruding 15–25 km inland until 5–6 ka, afterwards deltas prograded continuously with intermittent short periods of rise and fall in RSL during late-Holocene. In last two centuries, overall subsidence of 1.3–2.2 cm/yr is observed in Sundarbans, Bengal Basin leading to a 2.3 cm/yr estimated rise in relative sea level. The geological evidence of the 1008 CE tsunami in West Coast and earthquakes (Mw >8) in the historical past. Modern strength of oxygen minima zone around 1 Ma in denitrification and productivity records from the eastern Arabian Sea since late Miocene. Planktic foraminiferal assemblage and isotopic records from eastern Arabian Sea reveal a major reorganization in the south Asian/ Indian monsoon circulation attributed to the strengthening of Walker and Hadley circulation. Inter-hemispheric progression of deglaciation during ~130 ka by heat and moisture transfer from Southern to Northern Hemisphere in Bay of Bengal. Long-term impact of environmental changes on human health and subsistence have been revealed by sedimentary DNA analysis. Comparison of modern genome studies and those of Harappan / Indus Valley Civilization constructs the population changes in people of south Asia. MEGHALAYAN AGE : The Latest Stage in Earth’s 4.54 Billion-Year History Geologists divide up the 4.6-billion-year existence of Earth into slices of time. Each slice corresponds to significant happenings - such as the break-up of continents, dramatic shifts in climate, and even the emergence of particular types of animals and plant life. We currently live in what is called the Holocene Epoch, which reflects everything that has happened over the past 11,700 years - since a dramatic warming kicked us out of the last ice age. The Holocene itself can be subdivided, according to the International Commission on Stratigraphy (ICS) which is the official keeper of geologic time and it proposed three stages be introduced to denote the epoch's upper, middle and lower phases. These all record major climate events. The Meghalayan, the youngest stage, runs from 4,200 years ago to the present. It began with a destructive drought, whose effects lasted two centuries, and severely disrupted civilisations in Egypt, Greece, Syria, Palestine, Mesopotamia, the Indus Valley, and the Yangtze River Valley.It was likely triggered by shifts in ocean and atmospheric circulation. The Meghalayan Age is unique among the many intervals of the geologic timescale in that its beginning coincides with a global cultural event produced by a global climatic event. The Stratotype is housed in BSIP Museum .
