PHYSICAL GEOGRAPHY: EVOLUTION AND GEOLOGICAL FORMATIONS
The Asian relief is the result of the main geological events that have affected the Earth from the initial fragmentation of Pangea into two major continents: Laurasia to the North, Gondwana to South of reliefs that has its structural basis in the Angaric Shield and in the Sinic Shield, united, in the Paleozoic, to form the continent of Angara; to the second belonged the southern masses, that is, the Arabian and Indian peninsulas. The continent of Angara was separated from the western, north Atlantic section of Laurasia by a geosyncline from which the Hercynian reliefs of the Urals emerged; from other geosynclines that stretched along the edges of the continent of Angara, during the Caledonian and Hercynian orogenetic phases, the reliefs constituting the Kunlun Shan, the Tian Shan and the chains that border the Siberian region, including the Altaj mountains, the Saiani mountains and the transbajkalic chains, giving rise to the vast Siberian subsidence platform (Western Siberian Lowlands). Of these reliefs, the most internal are Caledonian, the most external and pronounced Hercynian. But the decisive event for Asia is linked to the formation of the great geosynclinal Tethys, which opened immediately to the South of the ancient reliefs and extended from the Mediterranean to China. Its evolution, which began in the Paleozoic, was responsible for the formation of the large and younger reliefs, such as Elburz, Hindu Kush, Himalaya, etc. The gigantic corrugation, which raised huge sedimentary masses accumulated in the geosynclinal pit, is part of a general crisis of the earth’s crust. In particular, it was connected to the movement of the Indo-Arab masses who, detached from Gondwana, moved towards the North, approaching the northern masses; the counter-thrust exerted by the Sinic and Angaric masses contributed to the particular development of the mountainous belt. The resulting relief, and which was defined above all in the Cenozoic era, is very complex. In fact, the whole mountainous belt is characterized both by real folded corrugations and covering faults intruded by gigantic crystalline masses, and by imposing vertical dislocations of interposed clods. To these dislocations we owe the formation of the highlands of Anatolia, Iran and Afghanistan, East Turkestan, Tibet, Mongolia itself, a tabular region between distant mountainous alignments.
After centuries in which the population, especially of East Asia, as defined by Countryaah.com, has lived in strong symbiosis with the surrounding environment, the recent and intense economic development – especially in the Indian region and the Chinese coast, without considering the intense mining activities of the region Siberian – has produced a long series of significant environmental changes. The portion of the territory subject to protection remains quite limited (5.7% of the territory in 2000), just as the establishment of protected marine areas is very recent (60% of the total that arose after 1980), which found mainly off the coast of Japan, China and the Korean peninsula. A typical example of how much anthropic activity is able to modify the environment is provided by what happened in China on the occasion of the Chang Jiang. In its middle course the river crosses, for 200 km, the famous region of the same name of the Three Gorges, before flowing into the eastern plain: the gorges have steep walls which, prior to the construction of the dam (2006), rose for 400-600 meters; with the creation of the artificial basin their height with respect to the course of the river has significantly decreased. Not only that, but the increase in river traffic and the alteration of natural balances have seriously compromised the existence of the local flora and fauna, as the case of the lipote (Lipotes vexillifer), a freshwater dolphin, declared extinct in 2006, although re-sighted in recent years. The other large area affected by strong industrialization, India, appears to be the country with the most compromised environmental situation in the entire Asian continent, primarily due to water and air pollution. In particular, water quality (due to the endemic spread of untreated sewage) and air quality (compromised by large industrial emissions) are of particular concern. The use of non-biodegradable pesticides also contributes to the contamination of soils, water and food. The whole continent has experienced strong deforestation in recent decades, which mainly affected the inland areas of India, of China and Southeast Asia. In India alone, deforestation affects about 1.5 million hectares of land every year and it is estimated that, considering only the data relating to Southeast Asia, the forests today cover only 53% of the territory occupied in 1985. rice is a typical crop of the eastern part of the continent, one of the plant species with the highest water consumption, the tendential and substantial increase in population pressure will seriously undermine the water management system: just think that a increase in water consumption which can range from 57% (South East Asia) to 70% (East Asia). A significant fact regarding anthropogenic air pollution is that concerning CO2 (carbon dioxide) emissions: the most recent data place China and India among the top five countries in order of emissions (China, with 24% of the total in 2007, holds the world record). This figure, which is understandable in the light of the economic model of these countries, will hardly face a reversal of the trend, since, so far, no one has been found.global governance to control and calm the phenomenon, as demonstrated by the outcome of the Copenhagen Summit, held at the end of 2009. In recent years, the limits of an often anarchic anthropization of some areas of the continent have been dramatically highlighted. Some disastrous events such as earthquakes (such as that of Bam, in Iran, in 2003 – over 30,000 dead – or that of Sichuan, China, in 2008, which cost the lives of about 90,000 people) or tsunamis (above all the devastating tsunami of 2004 in the Indian Ocean, about 230,000 victims), in fact highlight, alongside the terrible force resulting from natural events, also the absence of planning and foresight in the construction of civilian homes and in the occupation of spaces.