The jigsaw fit, one of the strongest evidences of Continental Drift Theory was propagated by A Wegener in 1912. Although remarked upon way back in 1620, with several scientists believing that the present day continents were the fragmented pieces of preexisting larger landmasses (supercontinents), it was only in the 1920s that the Theory gained prominence.

Earth’s crust is relatively lighter as compared to the denser mantle over which it lies and therefore behaves as if it is floating. Areas of the earth’s crust rise or subside to accommodate added load so that the forces that elevate landmasses balance the forces that depress them.

In recent years it has been possible to explore geological activity on the deep ocean floor. Using a submersible research vessel such as the United States’ Alvin, scientists have been able to make personal visits to deep sea sites rather than merely collecting samples from drilling. One of the most interesting discoveries made was ‘black smokers’ mineral enriched hot springs (or sometimes coloured white instead of black) from active regions of mid-oceanic ridges. They even have their own specially adapted marine animals and may be key sites for the origin of life on Earth.

Landslides frequently occur in about 15 per cent of India’s mountainous terrain, especially affecting the states of Sikkim and Mizoram.

Cyclones are areas of closed spiralling winds initiated by atmospheric disturbances around low pressure areas over the Indian Ocean, often resulting in destructive landfalls in the sub-continent. The air circulates inward in an anticlockwise direction in the northern and clockwise in the southern hemisphere.

Tsunamis are generated when the sea floor abruptly deforms and vertically displaces the overlying water. Recognising the imperative to put in place an early warning system for the mitigation of such disasters that cause severe threat to nearly 400 million of the Indian population that live in the coastal belt the Ministry of Earth Sciences has established a tsunami warning centre at Hyderabad.

Avalanches, a sudden rapid flow of ice/snow down a slope, occur in ice bound terrain. The frosty covering, precariously held to slopes, coupled with excessive amounts of snow layering and mixed with unpredictable weather patterns such as sudden warming are the makings of a disaster. The higher reaches of the Himalaya remain under a perpetual snow where thousands of avalanches occur, involving the movement of thousands of tons of ice and vertical displacements of over 1,500 metres.

Volcanic activities frequently occur along plate boundaries where pressure underneath the crust is released through cracks - pushing out magma and sometimes water and steam. The process of volcanism denotes eruption of molten rocks at the earth’s surface, often accompanied by rock fragments and explosive gases. Volcanism can take various forms, one being the creation of new crust along some 50,000 kms of ocean floor fissures where molten rock penetrates the surface and begins its divergent movement at the mid oceanic spreading ridges. In fact about 75 per cent of the world’s volcanoes are on the seafloor.

According to the provisional Census figures, although decadal growth in India’s population has registered the sharpest decline during 2001-2011, in terms of absolute numbers the population has increased by more than 181 million over the decade. India today sustains 17.5 per cent of the world population in 2.4 per cent of its geographical area.

People move in and out of places every day and have done so throughout human history. This short essay outlines the pattern of migratory movement and reflects an ever changing India. About 29 per cent of India’s population are migrants, which impacts the cultural landscapes in ways that often lasts well beyond lifetimes.