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Aeolian processes and landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Some 36 per cent of the world’s land surface is classed as dry savanna, semi-arid and arid; 19 per cent is arid and largely devoid of vegetation, and of this one-quarter to one-third is covered with mobile sand (Cooke and Warren, 1973). Wilson (1970) has shown that virtually all this mobile sand is contained in individual ‘sand seas’ or ergs (Arabic: erg – ‘region of shifting sand’) larger than 125 km2, and fully 85 per cent of it in ergs greater than 32,000 km2. The largest erg is the Rub al Khali in Arabia (560,000 km2) and the modal erg size is about 188,000 km2. Most sandy deserts are associated with the subtropical high-pressure cells and are located between latitudes 10° and 33°, the major exceptions being the Asiatic interior regions of Turkistan and the Gobi which lie far from maritime influences and experience high atmospheric pressure in winter. Some sandy deserts lie at quite high elevations (e.g. parts of Chile and Turkistan) and may be very cold in winter. The present areas of moving sand lie generally within the 150 mm isohyet and occur in a variety of tectonic environments, from the stable craton of the Sahara to the faulted basins of the south-western United States. In moister areas there are vegetated, stabilized tracts of ancient dunes indicative of climatic change (e.g. Nebraska Sand Hills, a broad belt south of the Sahara, and Botswana) (Figure 16.1). Desert sand derives from ephemeral stream channels and other fluvial deposits, coastal deposits, earlier dunes and from the weathering of sandstones and other siliceous granular rocks.
Sedimentary Environments and Facies
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Bedforms of various dimensions are produced by the action of wind: ripples (wavelength λ = 0.01–10 m), dunes (λ = 10–500 m) and draas (λ = 0.5–5.0 km). Each of these may be further subdivided into transverse and longitudinal elements leading to a total of eight subgroups, all apparently independent (Wilson 1972). A more comprehensive scheme of classification of eolian bedforms is given in Table 6.1 (after McKee 1979). Wilson’s draas are recognised in this scheme as the result of combination of two or more bedforms of the same type. Sand seas of still larger dimensions (~ 10,000 km2) are named ergs. These are produced by redistribution of sand initially deposited elsewhere.
Wind action and arid regions
Published in F.G. Bell, Geological Hazards, 1999
About one-fifth of the land surface of the Earth is desert (see Figure 8.1). Approximately four-fifths of this desert area consists of exposed bedrock or weathered rock waste. The rest is mainly covered with deposits of sand (Glennie, 1970). Desert regions may have very little sand; for example, only about one-ninth of the Sahara Desert is covered by sand. Most of the sand that occurs in deserts does so in large masses referred to as sand seas or ergs. In fact, Wilson (1971) estimated that 99.8% of aeolian sand is found in ergs that exceed 125 km2 in area, and 85% is in ergs greater than 32 000 km2. The smaller ergs, according to Cooke and Warren (1973), include dunes of one type only, but most ergs have different patterns of dunes in different areas.
Interconnecting sustainable development goals 7 and 13: the role of renewable energy innovations towards combating the climate change
Published in Environmental Technology, 2023
Hafiz Waqas Kamran, Mujahid Rafiq, Anas Abudaqa, Azka Amin
Table 8 also reveals that ERG reflects statistically significant coefficients. More specifically, the results show that the impact of ERG on EFP is highly significant, specifically under 0.50th and 0.75th quantiles with relative coefficients of −0.117 and −0.216. Moreover, ERG compels the overall economic structure to transform while utilizing environmental resources more efficiently. Such efforts may generate possible short-term growth loss; however, a successful ecological transformation may result in cleaner production in the medium and long run. Our results are aligned with Aşıcı and Acar [26]. They consider the sample of 87 countries and claim that strict and enforced ERG reduces the income turning point of the non-carbon footprints. Additionally, such regulations push toward the exploitation of natural resources more effectively. Relatedly, Luo and Mabrouk [35] focus on resource-rich economies and claim that ecological regulations reduce the EFP in the long and short run. Based upon the current empirical findings, the environmental reasoning behind ERG-EFP relationship clears that environmental policies and measures limit the harmful human activities conducted by business groups or economies in the form of depletion of natural resources and more pressure on nature. For this reason, ERG controls natural degradation through emission standards, land use restrictions, and waste management.