When few months are left for UPPSC Prelims 2021, it becomes very important for every aspirant to be on their toes and follow an organized plan which will help them clear this exam and keep them at ease during the preparation phase.
UPPSC Target PT in 90 Days Planner will provide you with a daily time table, which will comprise of the following:
Landforms and its Evolution
Processes involved in the river erosion
The Course of a River
Potholes and Plunge Pools:
Incised or Entrenched Meanders
Typical landforms formed by the work of river
Process of underground water forming various features
Yardangs are narrow, streamlined ridges that are usually three to four times longer than they are wide. They are made up of long ridges of hard resistant rocks alternating with narrow furrows of soft rocks. Here, both the bands of hard and soft rocks aligned vertically to the direction of the blowing prevailing winds. The process of abrasion is accelerated in the course of the blowing prevailing winds, assisting in wearing the soft bands of rocks into narrow corridors between the hard layers. Eventually, the bands of hard rocks remain standing high above the soft bands that have been worn into narrow corridors.
A zeugen is a tabular mass of resistant rock, standing prominently in the desert. It is usually composed of alternating layers of hard and soft rocks. These alternating bands of rock usually lie horizontal on top of one and another. The softer rock layer usually lies beneath a surface layer of more resistant rock. The sculpturing effects of wind abrasion wear them into a furrow and ridge looking landscape. Insolation weathering enhances this activity.
Playas are by far the most prominent landforms in the deserts. In basins with mountains and hills around and along, the drainage is towards the centre of the basin and due to gradual deposition of sediment from basin margins, a nearly level plain forms at the centre of the basin. In times of sufficient water, this plain is covered up by a shallow water body. Such types of shallow lakes are called as playas where water is retained only for short duration due to evaporation and quite often the playas contain good deposition of salts. The playa plain covered up by salts is called alkali fiats.
Deflation Hollows and Caves
Weathered mantle from over the rocks or bare soil, gets blown out by persistent movement of wind currents in one direction. This process may create shallow depressions called deflation hollows. Deflation also creates numerous small pits or cavities over rock surfaces. The rock faces suffer impact and abrasion of wind-borne sand and first shallow depressions called blow outs are created, and some of the blow outs become deeper and wider fit to be called caves.
Mushroom, Table and Pedestal Rocks: Many rock-outcrops in the deserts easily susceptible to wind deflation and abrasion are worn out quickly leaving some remnants of resistant rocks polished beautifully in the shape of mushroom with a slender stalk and a broad and rounded pear shaped cap above. Sometimes, the top surface is broad like a table top and quite often, the remnants stand out like pedestals.
Wind is a good sorting agent. Depending upon the velocity of wind, different sizes of grains are moved along the floors by rolling or Saltation and carried in suspension and in this process of transportation itself, the materials get sorted. When the wind slows or begins to die down, depending upon sizes of grains and their critical velocities, the grains will begin to settle. So, in depositional landforms made by wind, good sorting of grains can be found. Sand accumulations come in a range of sizes and forms. Deposition may occur as sheets of sand (dune fields and sand seas) or loess or as characteristic dunes.
Ripples: Wind ripples are the smallest Aeolian bed form. They are regular, wave like undulations lying at right-angles to the prevailing wind direction.
Loess: Loess is terrestrial sediment composed largely of windblown silt particles made of quartz. It covers some 5-10 per cent of the Earth’s land surface, much of it forming a blanket over pre-existing topography that may be up to 400 m thick. Loess requires three things:
Dunes: Dunes are collections of loose sand built piece meal by the wind. They usually range from a few metres across and a few centimetres high to 2 km across and 400m high. Sand dunes form where there is a source of sand. Dune sand is usually composed of quartz, which is extremely hard and doesn’t easily decay. Dune sand grains are beautifully rounded by abrasion.
Crescent shaped dunes called barchans with the points or wings directed away from wind direction i.e., downwind, form where the wind direction is constant and moderate and where the original surface over which sand is moving is almost uniform. Parabolic dunes form when sandy surfaces are partially covered with vegetation. That means parabolic dunes are reversed barchans with wind direction being the same.
Seif also called linear dunesis similar to barchans with a small difference. Seif has only one wing or point. This happens when there is shift in wind conditions. The lone wings of seifs can grow very long and high. Longitudinal dunes form when supply of sand is poor and wind direction is constant. They appear as long ridges of considerable length but low in height.
Transverse dunes are aligned perpendicular to wind direction. These dunes form when the wind direction is constant and the source of sand is an elongated feature at right angles to the wind direction. They may be very long and low in height. When sand is plenty, quite often, the regular shaped dunes coalesce and lose their individual characteristics. Most of the dunes in the deserts shift and a few of them will get stabilised especially near human.
Wave action in deep and shallow water
Various coastal landforms
Various landforms formed by glacial action
Glaciers are capable of carrying a huge amount of rock debris over considerable distances. Glacial deposition is mainly of two types: deposition directly from the ice after melting; and by melt water flowing from a glacier.
90 Days Planner (Day 27 Geography)