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Volcanoes, Tectonics and Climate
In this section the relationships between some aspects of tectonophysics and climate are going to be briefly reviewed. Tectonophysics is concerned with movements in the Earth's crust, examples of such processes include the formation of sedimentary basins, postglacial rebound of regions such as Fennoscandia, earthquakes, plate tectonics, mountain building (i.e. orogenesis), volcanoes and volcanic events. Of these various phenomenons, some can have a short-term and a long-term effect on climate while others have only an impact on longer time-scales, though a very significant one. Volcanoes and volcanic phenomenons are remarkable as they have both a short-term and long-term impact depending on the type of events considered. Plate tectonics, and orogeneses have major long-term impacts as they change all circulations on Earth, be they atmospheric or oceanic and as these circulations regulate largely the distribution of energy and heat on the planet (and not only on a meridional scale), they set the patterns that define the global and regional climate(s). The erosion and alteration rates of silicate rocks depend on the latitudinal position and organization of the continents and of the climate observed where they are situated and therefore plate tectonics and orogeneses contribute to influence marginally the composition of the atmosphere by a variable withdrawal rate of CO 2. A lot of emphasis has been placed on these issues as a result of the excessive focus of the early XXI century research on the supposedly warming effect of CO2. The position of the plates, their organization and therefore their impact on the oceanic circulation, the obstacles and incidences that mountain belts have on the atmospheric circulation, all have a far greater impact on the climate than whether more of less CO 2 is withdrawn by erosional and alteration processes that were described in the section “CO2 removal from the atmosphere”, starting page 52. Trying to explain the Cenozoic or worse, e.g. the Cretaceous climate up to 145 million years ago by whatever changes of CO 2, be they of the order of ±1,000 or even ±2,000 ppm, are not relevant as was stressed in the “Past Climate” sections pages 130 and 138. One should remember the paper of Zachos et al., (2003) stating “Thus, these findings reinforce the hypothesized greenhouse gas forcing for the PETM. Whether the primary radiative forcing was supplied directly by CH 4 and / or CO2 is still unknown. The carbon isotope excursion has been attributed to the expulsion… of CH 4 from gas hydrates... assuming that the CH4 was converted to CO2, numerical models indicate a modest rise in atmospheric p CO 2 (100 ppmv), an amount far below that required to drive the observed warming... This suggests either that the CH 4... escaped immediate oxidation in the ocean and accumulated in the atmosphere, that the mass of CH 4 released was substantially greater (> 4 x 10 3 Gt) than estimated, and/or that additional greenhouse gas (CO 2) was supplied by another source”. When one needs a combination of three “Deus ex machina” to fit the bill when numbers cannot add up, it means that one is looking under the GHG lamppost, because this is where the light is supposed to be, but that no solution will be found there. One needs more imagination to fathom what these distant worlds could have been and tectonophysics is the discipline that helps build mental representations and frames that organize thought in that respect. Of all the relevant phenomenons, this section will only briefly deal first with volcanism and volcanic events and then with how plate tectonics might have impacted by their relative positioning and ordering the circulations and climate patterns. Apart from geologists and planetologists who do not need it, volcanoes with the earthquakes are the two manifestations having an internal origin that remind our contemporaries that the Earth is an active body (Zobin, 2018). In fact, hot springs also tell the same story and could serve as a reminder. Volcanoes are a source of awe and fear and history of mankind has always showed a conflicting stance as fertile terrains have always attracted men for good agricultural reasons while at the same time leading them to being too close of dangerous and massive objects. From time to time, alas, one of these monsters erupts and as was previously mentioned, Naples, beyond its famous pizza(s) is well known for the ominous and dreadful Vesuvius eruption in 79 Anno Domini (AD) with a VEI=5. I personally live in Malta, located just 70 km away from Mount Etna, the highest active volcano in Europe outside the Caucasus, a stratovolcano of 3,326 m (10,912 ft), being about two and a half times the height of the next largest, Mount Vesuvius. On clear days, one can see the top of the volcano stand out well above the blue horizon of the Mediterranean sea. Etna occupies a very special geodynamical position, it lies above the convergent plate margin between the African Plate and the Eurasian Plate and volcanic activity started about 500,000 years ago, and about 300,000 years ago, volcanism began occurring to the southwest of the current summit, then activity moved towards the present center 170,000 years ago. Eruptions at this time built up the first major volcanic edifice, forming a strato-volcano in alternating explosive and effusive eruptions leading to the collapse of the summit to form calderas. From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large pyroclastic flows, which left extensive ignimbrite deposits (i.e. a hardened tuff, a pyroclastic rock of dacitic or rhyolitic composition). Ash from these eruptions has been found as far away as south of Rome's border, 800 km (497 mi) to the north. Thousands of years ago, the eastern flank
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