Major landforms of the earth

Efforts by Aagman Saini

The various landforms are formed by various endogenic forces. However, the exogenic forces tend to reduce the elevation of the existing landforms. The exogenic forces are carried out in two ways:-

Weathering Erosion

Landform

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity.Two important classifications of weathering processes exist – physical and chemical weathering; each sometimes involves a biological component. Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure. The second classification, chemical weathering, involves the direct effect of atmospheric chemicals or biologically produced chemicals (also known as biological weathering) in the breakdown of rocks, soils and minerals.The materials left over after the rock breaks down combined with organic material creates soil. The mineral content of the soil is determined by the parent material, thus a soil derived from a single rock type can often be deficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types (as in glacial, Aeolian or alluvial sediments) often makes more fertile soil. In addition many of Earth's landforms and landscapes are the result of weathering processes combined with erosion and re-deposition.

Weathering

Erosion is the process by which soil and rock are removed from the Earth's surface by exogenetic processes such as wind or water flow, and then transported and deposited in other locations.While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive erosion causes problems such as desertification, decreases in agricultural productivity due to land degradation, sedimentation of waterways, and ecological collapse due to loss of the nutrient rich upper soil layers. Water and wind erosion are now the two primary causes of land degradation; combined, they are responsible for 84% of degraded acreage, making excessive erosion one of the most significant global environmental problems.Industrial agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many available alternative land use practices that can curtail or limit erosion, such as terrace-building, no-till agriculture, and revegetation of denuded soils. thus, different landforms are created by the agents of erosion

Erosion

Rivers perform a tremendous amount of work by erosion, the wearing away of the land's surface. All river water carries dissolved minerals and tiny particles of silt and clay. When the current of the stream is fast enough, it carries sand, gravel, and even boulders by suspension and by rolling them along the river bed. Thus the greater the speed and amount of water, the heavier the load the river can carry. Part of the material carried is washed into the stream; part is removed by the river itself from its banks and bed. In large rivers, such as the Mississippi, the amount of eroded material carried to the sea amounts to hundreds of millions of tons annually.Rivers vary greatly in the amount of water carried. In regions of ample rainfall, they flow throughout the year. They receive water directly during rains; they have many tributaries; they receive ground water, which has seeped into the land during rains; and they are constantly fed by lakes, swamps, marshes, and other wet areas. The greatest volumes of water are carried by the Amazon River of South America and the Congo River of Africa. Both drain vast areas of rainy tropical land. In dry regions, rivers usually flow only after rains, which often come in downpours causing flash floods.Rivers are of value in different ways throughout the world. In Southeast Asia, the fertile soils of the valleys of the Mekong, Salween, Irrawaddy, and Ganges support regions having some of the world's highest population densities. In Europe, the Rhine, Elbe, & Seine, and their many connecting canals, provide a fine system of river transportation. In North America, rivers are used extensively for transportation, water power, and irrigation. The major rivers of Africa, northern Asia, and South America are generally used less than rivers elsewhere because the lands through which they flow are sparsely populated

Work of a river

Waves give rhythm to the ocean. They transport energy over vast distances. Where they make landfall, waves help to sculpt a unique and dynamic mosaic of coastal habitats. They impart a watery pulse upon intertidal zones and trim back coastal sand dunes as they creep towards the sea. Where coasts are rocky, waves and tides can, over time, erode the shoreline leaving dramatic sea cliffs. Thus, understanding ocean waves is an important part of understanding the coastal habitats they influence. In general, there are three types of ocean waves: wind-driven waves, tidal waves, and tsunamis.

Work of sea waves

The impact, over the last million years or so, of a series of glaciations extended across much of western Europe. The most recent of these glaciations saw ice, on occasion in excess of a thousand metres thick, covering most of Ireland. These glaciations had a huge impact, as a result of the erosive work of slow-moving ice and also a result of depositional activity under the ice and at its margins.

The most widespread glaciation built up as a dome across much of lowland Ireland. Some mountain areas, for example in Cork-Kerry and in Wicklow had their own separately-driven ice caps. A few areas, mainly in parts of the south, remained unglaciated. Some of the most striking mountain scenery has been moulded by glacial erosion, although its precise expression relates also to the geology (contrast the pointed sandstone Kerry Reeks with the gently rolling profiles of the granite mountains of Wicklow and Mourne).

The evidence of glacial erosion is widespread in many mountain areas. Over-deepened rock hollows, some of them water-filled, represent the corries or cooms, where snow first lay, thickened and nourished ice. From these locations ice advanced into and down valleys. To these locations, the ice retreated. Two of the most spectacular corries are the Devil's Punchbowl, on Mangerton Mountain in Co. Kerry, and Coomshingaun, in the Comeragh mountains of west Waterford, but these features are widely-distributed in mountain areas. In west Mayo up to sixty small corries can be counted. Near Dublin, good examples are upper and lower Lough Bray , and Lough Tay, making steep rock faces that punctuate the generally rounded Wicklow mountains.

Work of moving ice

Features formed during glaciation

Features formed after glaciation

Wind is one of the major agents of the change on the surface of the earth, other two being river and glacier. The changes are mainly brought due to their movement and during such movement it may causes temporary or permanent changes. These changes manifest themselves in the form of surface features ,their exact nature depending on the velocity of the wind, its volume, nature of the surface and its duration of time for which it blows and so on. Thus, strong winds blowing over loose surface, dry soil and over desert may create temporary new features. Wind acts as an agent of erosion, as a carrier of transporting particles and grains so eroded from one place and also for depositing huge quantities of such wind-blown material at different places. The three principle modes of activity, i.e.…, erosion, transportation, and deposition by wind are briefly discussed below.

Work of wind

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