The futur of the earth

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  • Publicado : 16 de marzo de 2010
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IF GEOLOGICAL PROCESSES ARE GOVERNED BY UNIVERSAL PHYSICAL LAWS, SHOULD THE HISTORY OF THE EARTH BE PREDICTIBLE?
By Sebastián Ramiro Ramírez If one were to answer the question, bearing in mind that nowadays we assume that geological processes are governed by universal physical laws, and that the always behave in the same manner, then the answer would be yes. That is, considering “standard” or“ideal” conditions, or in other words, that the system intender for study is not affected by external perturbations. However, these ideal conditions do not take place in nature. For instance, take the erosion process of a drainage basin (with a given flow, slope and composition), in theory, it could be predicted how it will be eroded and the morphology it will adopt with the passage of time. However,if the external perturbations are kept in mind, for instance, the climate factor, then, the evolution of such drainage basin will not be 100% predictable any more. Hence, the question is weather external factors are predictable over time, and the answer is yes and no. All along the history of the Earth, after several studies and verifications, it has been shown that the evolution of climate has atendency to decrease the temperature and the atmospheric CO2. However, sometimes there are certain perturbations that affect directly the erosive processes. Such is the case of the Milankovitch Cycle, with a regular recurrence of 100,000 years (since at least 3Ga), by which it can be explained why glaciation episodes take place on the earth: the contrast between seasons is vital for the formationof glaciers, and in turn this depends on the ellipticity of the Earth´s orbit around the sun. The bigger the ellipticity the bigger contrast, with warmer winters (bigger amount of snow fall) and colder summers (smaller fusion of glaciers). When there is a strong ellipticity, the earth enters a period of glaciation. Now the question would be what the relationship is between this and CO2 anderosion. The answer then would be that this influences directly the alteration and erosion of calcium silicates contained in the mountain ranges and the erosion of rivers. Since there is no water to transport the CO2 in order to alter the CaSiO4, and erosion that the river flow produces in the drainage basins, there is a certain period of time when the erosion processes stop, and this will be so until avolcanic eruption takes place. Therefore, it is possible to make an approximate prediction of when such an event will take place on the Earth, but not how long will pass before the Earth goes out of it. There are other processes that take place in a cyclical way since at least 15,000 years ago. That is the case of the well-know phenomenon of “El Niño”. This causes enormous floods in thecontinental areas of Central and South America, able to change a drainage basin, and hence, its morphology. In this case, it is possible to know approximately time of the year this phenomenon will take place, and also its periodicity. However, the effect it will have on the Earth´s morphology is something aleatory. Another important factor to consider is the Tectonic Plates Theory, which explains the way inwhich the Earth´s lithosphere is structured. This theory deals with the tectonic plates that form the surface of the Earth, and how they move along the mantle, their direction and interactions. It also explains how mountain ranges are formed, and why volcanoes and earthquakes concentrate on certain places of the Earth, and also, why the great oceanic trenches are nearby islands and not in themiddle of the ocean.

This poses a new question: does this theory provide a logical explanation merely to the processes that took place in the past and the ones that are taking place in the present? Or does it also allow to make predictions about what will happen in a thousand or a million years? Considering the fragmentation that took place after the last pangaea, and the subsequent evolution...
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