Answer: Masses of ice moving as sheets over the land or as linear flows down the slopes of mountains in broad trough-like valleys are called glaciers. They are formed through the processes of accumulation, compaction, and recrystallization of snow. The movement of a glacier is very slow and it moves from a few centimeters to a few meters in a day. During this movement, a glacier forms various landforms. Erosional landforms created by the movement of a glacier are the following:

• Glacial Valleys/Troughs: Glaciated valleys are trough-like and U-shaped with broad floors and relatively smooth, and steep sides.
• Cirque: These are bowl-shaped depressions found at the head of glacial valleys. For most alpine glaciers, cirques are the areas where snow first accumulated and was modified into glacial ice. A lake found in a cirque is called a tarn.
• Horns: These are pyramidal peaks that form when several cirques chisel a mountain from three or more sides. The highest peaks of the Alps (Matterhorn) and the Himalayas (Everest) are in fact horns formed through headward erosion of radiating cirques.
• Arete: These are formed as a spiky high land between two glaciers.
• Valley step: It is an abrupt change in the longitudinal slope of a glacial valley.
• Bergschrund: These form when a crevasse or wide crack opens along the headwall of a glacier; most visible in the summer when covering snow is gone.

Depositional landforms created by the movement of glaciers include:

• Till deposits: The unassorted coarse and fine debris dropped by the melting glaciers is called glacial till. Most of the rock fragments in the till are angular to subangular in form.
• Outwash plains: Streams form by melting ice at the bottom, sides, or lower ends of glaciers. Some amount of rock debris small enough to be carried by such melt-water streams is washed down and deposited. Such glaciofluvial deposits are called outwash plains.
• Moraines: They are long ridges of deposits of glacial till. Based on their orientation with the glacier, they are termed terminal moraines, lateral moraines, horse-shoe-shaped ridge, ground moraines, and medial moraines.
• Eskers: These are sinuous ridges formed as a result of the melting of ice. During summers, the water accumulates beneath the glacier and flows like streams in a channel beneath the ice. This causes very coarse materials like boulders and blocks along with some minor fractions of rock debris carried into these streams and settle in the valley of ice beneath the glacier giving rise to eskers.
• Drumlins: Drumlins are smooth oval-shaped ridge-like features composed mainly of glacial till with some masses of gravel and sand.

Answer: Diastrophism is an endogenic process and consists of all processes that move, elevate, or build up portions of the earth’s crust. It is the process that brings about changes in the configuration of the surface of the earth. They move, elevate, or build up portions of the earth’s crust owing to the energy emanating from within the earth. This energy is mostly generated by radioactivity, rotational and tidal friction, and primordial heat from the origin of the earth. The process of diastrophic movements is of the following types:

• Orogenic processes: These involve mountain building through severe folding and affecting long and narrow belts of the earth’s crust. This process takes place when tectonic plates collide, separate, or slide along one another. This causes mountain building through severe folding and affects long and narrow belts of the earth’s crust. Some examples of ongoing orogenic processes are the Mediterranean ridge, Andean orogeny, the Himalayan progeny, etc.
• Epeirogenic processes: These processes involve the uplift or warping of large parts of the earth’s crust. They involve a strictly vertical movement of a continent rather than horizontal movement and also uplifting or warping large parts of the earth’s crust. These processes lift the whole region evenly and result in the formation of gentle arches and structural basins.
• Plate tectonics: These involve horizontal movements of crustal plates. The outer shell of the earth i.e., the lithosphere is broken up into tectonic plates. Plates are classified as major, minor, and micro. Plate tectonics is simply the process of horizontal movement of these plates. The current physical map of the world with the distribution of continents and oceans is the result of the plate tectonic process.
• Earthquakes: They involve relatively local minor movements. Earthquakes occur when the surplus accumulated stress in rocks in the earth’s interior due to folding, faulting, or other physical changes is relieved through the weak zones over the earth’s surface in the form of kinetic energy (seismic waves). Such movements may result in uplift or subsidence in coastal areas.

Through the processes of orogeny, epeirogeny, earthquakes, and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure, volume, and temperature (PVT) changes which in turn induce the metamorphism of rocks.

Answer: A landslide is the movement of a mass of rock, debris, earth, or soil (soil being a mixture of earth and debris) on the downslope. Landslides occur when gravitational and other types of shear stresses within a slope exceed the shear strength (resistance to shearing) of the materials that form the slope. They often take place in conjunction with earthquakes, floods, and volcanoes. Prolonged rainfall is one of the most important triggers. The two regions most vulnerable to landslides in India are the Himalayas and the Western Ghats. There are several differences between the landslides of the two regions, including:

• Reasons for the occurrence of landslides:

• • The Himalayan mountain belt comprises tectonically unstable younger geological formations subjected to severe seismic activity. Also, the northward movement of the Indian plate causes continuous stress on the rocks rendering them friable, weak, and prone to landslides.
  • In the Western Ghats, almost all mass movements occur during monsoons (South-West and North-East monsoons) in the western flank and, during occasional cyclonic events in the eastern flank indicating that the main triggering mechanism is the over-saturation of overburden caused by heavy rains. Their steep seaward slopes are deeply dissected by streams and canyon-like valleys. Further, pronounced mechanical weathering due to temperature changes and ranges along with high-intensity rainfall during the monsoon trigger landslides.

• Nature of landslides: Compared to the Western Ghats region, the landslides in the Himalayan region are huge and massive, and in most cases, the overburden along with the underlying lithology is displaced during sliding particularly due to the seismic factor.
• Frequency of occurrence: Landslides occur very frequently in the Himalayas whereas they are not that frequent in the Western Ghats.
• Slope instability: The Himalayan region has high slope instability due to the immature and rugged topography. Compared to that, the Western Ghats are geologically stable and are mostly made up of very hard rocks, but have uplifted plateau margins influenced by neo-tectonic activities that provide a gradient for the landslides.

Although the causes of the landslides in the regions are different, the devastation caused by them is similar. Other than that, increased anthropogenic activities in terms of infrastructure development, construction of dams, and quarrying and mining in both the regions are inflicting heavy damage to the slopes. Thus, management of landslides would require coordinated efforts by limiting anthropogenic activities, as well as closely cooperating with all the stakeholders in the disaster management cycle.