| Volcanic activity is perhaps the single most important geological phenomenon for life and living beings on our planet.Volcanic eruptions were – and still are – among the most thrilling natural phenomena that attracted, scared and fascinated humans. It is no surprise then that volcanic eruptions are among the first themes drawn by Neolithic civilizations in murals found in Central Anatolia conurbations, 8,500 years ago. Volcanoes were the first main provider (along with lightning) of fire, a tool invaluable to man. Volcanoes were the origin of obsidian, the ‘precious stone’ of the Neolithic age. They then supplied volcanic ash that permitted the production (after mixing with lime) of the first cement that could cure and resist water. The sulfur they produced was the best disinfectant, a key medicine for viticulture and gardening. They permitted quarrying of millions cu. m. of high-strength, beautiful rocks used to build bastions and fortresses, temples and dwellings. Hot springs were on or adjacent to volcanoes; they became famous for healing all diseases. Volcanic soil was the most fertile of all, allowing two or three crops a year if sufficient water was available. Volcanoes are of course linked to catastrophic effects too. Despite the fact that volcanic activity – related risks were much lower compared to other natural disasters, the numbers of victims and devastation caused by major volcanic eruptions are significant. Unfortunately, we are ‘minuscule on our Earth to clean up our volcanoes’ as the Little Prince of Antoine de Saint Exypery did on his own small planet. Yet volcanic eruptions are among the physical disasters for which the current state of knowledge permits long-, mid-, and short-term predictions. Assessment of volcanic risk and hazard levels become increasingly more accurate and permit us to minimize casualties.All the tribes on our planet, through all ages, invented countless myths that deify volcanic activity. Hundreds of novels have been scripted and thousands of meters of film have recorded imaginary or actual extravagant scenes of creative or ravaging volcanic activity. The one and only Jules Verne used them as gates to the knowledge of the Earth’s interior. His ‘journey’ to the ‘center of the earth’ starts with a descent in a volcanic crater in Iceland; return to the surface is made when explorers are blasted from the crater of Stromboli, in the Aeolian Islands of Italy. 150 years after the novel was scripted, Stromboli continues its eruptions at approximately 20 minute intervals to remind us just how lively our planet is. At 20 minute intervals, it blasts new flaming magma that feeds a quite intricate chain in the earth crust, in the water and in the air, which keeps our planet alive through a fragile dynamic equilibrium.Compared to the trip imagined by Jules Verne, it is amazing to note that all elementary particles that compose our body have made this very trip! The stardust of which we are made has been many times recycled from the surface to the inside of earth and has been blasted over and over from volcanic craters before it started to assume the form of living material.Astrophysicists have yet to conclude the prevailing model for the creation of our planet (consolidation of cosmic matter, homogenous or not), however they agree that in the past phases of creation, there has been sufficient heat to turn its outer jacket into molten fluid. A few million years after its creation, our planet was surrounded by a ‘magmatic ocean‘: All lighter rock elements amassed in the exterior surface were in a viscous, incandescent condition.As Earth began to cool by radiating heat to the universe, the topmost magma started to solidify and create the initial rocky crust. This primordial crust is highly unstable, as it floats above an ocean of magma. It is broken into large solid plates, the planet’s initial tectonic plates. Magma under the crust found ways to the surface through the cracks that separated the plates and thus it poured out or ejected to the surface to become cooler, solidify into lava and build up thousands of new volcanoes, adding substantial large blocks of solid rock to the crust.It took another 300-400 million years until the production of continental crust began, from new volcanoes and form the erosion of older ones, through the physical and chemical differentiation of magma; it then formed terrestrial lands as it surfaced above the primordial oceans and composed the first continents. Continental crust is a unique feature of Earth. Other ‘rocky’ planets in the solar system (Mercury, Venus & Mars) as well as our satellite (Moon) lack such a crust. Its existence on Earth is owed to two elements: the presence of water and the plate tectonics. Water weathers and erodes older rocks, simultaneously hydrating the basaltic crust. Plate tectonics cause the subduction of a slab below another and produce lighter ‘orogenic’ magma which is then cooled, consolidated and piled up, thus creating the continents. Thereafter, by virtue of the plate tectonics mechanism, volcanoes create, renew and partially recycle earth crust. Assuming that our planet is 100 years old – to adjust this magnitude to the human timescale – it renews its surface each 3.5 years. Thus, a multiplicity of geo-ecosystems is created; the variety of life forms on the planet is attributed to this multiplicity. It is possible that life on Earth would not develop without plate tectonics. Even if it could develop without them, in all probability it would not develop to such diversity culminating to mankind itself. Plate tectonics was non-existent – or stopped very early – on other rocky planets in the solar system. Based on current state-of-knowledge and thermal status of our planet, we can infer that it will remain alive (with intense volcanic activity and earthquakes) for at least 500 million more years. Then, it will become a dying planet, presumably as Venus is today.A key factor that contributed in transforming Earth into a living planet is the composition of the atmosphere; in this area too, volcanoes played a vital part. Most scientists that study genesis and changes to the earth’s atmosphere accept that the initial atmosphere of our planet does not exist any more. Light gaseous elements that remained attached during the initial consolidation phases were eventually swept by the ‘Taurus wind’, a cosmic hurricane from the sun, when its nuclear firing became stable, as the case is with all stars. Thus, our current atmosphere was born from the gases released through volcanic eruptions during the Earth’s life span, following the ‘Taurus wind’ effect, perhaps with small contributions by ice meteoroids which brought water from space.An initial approach for estimating gases produced by 4.5 billion years of volcanic activity reveals astonishing facts: the resulting quantities of water, chlorine, nitrogen and carbon are almost tantamount to the sum of these elements in the current atmosphere, water environment and the sediments on the earth crust (where large carbon dioxide quantities are blocked in limestone). Two elements are an exception to this: oxygen and sulfur: the first is not produced from volcanoes while the second is produced in quantities much larger than the ones found today. Regarding oxygen, it is known today that its production started from living matter (the term being used conditionally upon its schematic definition as self-reproducible organic matter), by being amassed in small percentages just 2.5 billion years ago, initially as a (by)product of bacterial fermentation and later – in mass quantities – as a product of photosynthesis. Things are not as clear with respect to sulfur. Based on the above calculation, the quantities of sulfur in the atmosphere, water environment and the earth crust sediments should be 50 times more than they actually are. This would mean large quantities of sulfuric acid, a factor that would prevent the existence of most of the current living forms. Apparently it is iron and plate tectonics that saved us: the former retains sulfur to produce pyrite while plate tectonics make sure that sulfur is removed by being recycled to inner earth.The invigorated power of volcanoes is not restricted to renewing the ocean earth crust, increasing the continental crust and feeding the planet’s atmosphere and water environment. An increasing number of scientists studying the mystery of the creation of life, the structuring of the primordial forms of living matter, assert that the volcanic environment is the most appropriate for the development of life-creating conditions.Despite the amazing variability of living organisms, they comprise very few elements (mainly carbon, oxygen, hydrogen, nitrogen and phosphor) organized in also few organic compounds (mostly nucleic acids, proteins, hydrocarbons and lipids). RNA and DNA, two composite nucleic acids are responsible for reproduction as they contain the resources and experience of the past as well as the instructions to use it. The following are requirements for life creation: (1) existence of the required elements, catalysts and energy to compose organic molecules; and (2) absence of free oxygen that could oxidize and destroy these molecules. The first and most widespread theory of the condensed ‘primordial soup’, rich in carbon compounds, which, aided by lightning energy and ultraviolet radiation, composed organic molecules, appears to be troublesome. The rapid recycling of the first oceans through the mid-oceanic ridges appears to prevent the development of such a soup, except for few and special conditions (isolated basins exhibiting intense evaporation). Though a group of astrochemists is contemplating the possibility that living matter was imported from outer space, several scientists estimate that the environment in which living matter was structured was far more expanded and widespread in the early archaic age. The path that led from inorganic matter to aminoacids and then to RNA (assuming that it preceded proteins) requires stable long-term conditions and continuous supply of energy and raw matter, as well as appropriate structures in the environment that will allow accommodation and aid forming of the structure of organic substances. The optimal environment that features all the above characteristics is areas of widespread hydrothermal activity along the underwater volcanoes on mid-oceanic ridges. These demonstrate a continuous presence and production of water, carbon dioxide, ammonia, hydrogen sulphide and methane. Heat is continuously supplied. The minerals produced from weathering of basalts – clay minerals and zeolites – serve as catalysts: using the slates comprising the former or the pores – tunnels featured in the crystalline structure of the latter, they offer appropriate places and also direct the organic matter to its organized structuring. Thus, they provide an opportunity to germinate and safely store the chains that we discovered in our time within RNA and DNA structures. Thus, the first living organism, 4 billion years later, seem to have developed in zeolites and the clayey minerals of ‘white smokers’, spectacular hydrothermal manifestations that have recently been photographed by submarines that have explored the active volcanoes on mid-oceanic ridges.In the last 20 years, the dramatic increase in carbon dioxide emissions from burning fossil fuel and the production of CFCs opened up a wide and varied debate regarding the greenhouse effect, the depletion of ozone and eventually the possibility that man-induced activities destabilize the equilibrium that the planet has created and maintained for billions of years. Scientists, in an effort to provide a precise quantitative estimate of the physical time-specific variation and change of climate, in order to enable the assessment of man-induced impact, turned their attention to the role of volcanic eruptions upon climate change.Active volcanoes on our planet are currently estimated to exceed 550. Around 60 of them explode each year, releasing volcanic ash to the atmosphere. Some are continuously active e.g. Stromboli, Etna and Hawaii; they constantly release – whether explosively or not – enormous quantities of volcanic gases. Whether these affect the climate and the ozone layer and to which extent and over which time period – and whether such influence is cumulative or not, and whether the changes these bring are dependent upon magma composition, eruption magnitude or the location of the volcano on the planet, are questions yet to be answered to produce adequately reliable models that will simulate the natural climate changes over time.In fact, a qualitative approach to this issue is far older. In 44 B.C., the year Julius Caesar was assassinated, a vast eruption of Etna caused the spreading of a thick, dry cloud that extended to Rome. Plutarch reports that that year sun rays were so foible and cold that fruit was unable to ripen. The next year is referred to as an unusually cold year; crops were reportedly ruined in Italy and Egypt. One thousand eight hundred years later, in 1789, Benjamin Franklin attributed the cause for the cold winter of 1783/84 to a blue fog that covered northern Europe, derived from the major eruption of Laki volcano in Iceland. In 1815, Tampora volcano, east of Bali island in Indonesia, erupted to release in excess of 40 cubic kilometers of magma into the atmosphere. This was one of the largest eruptions on Earth witnessed by humans. 1816 is referred as the ‘year without summer’. A dry blue fog is described in New York. Cold weather would force Mary Shelley to make creative use of her summer vacation, thus creating “Frankenstein”. The subject again made it to the forefront in 1883, when Krakatau volcano in Indonesia exploded. The conclusion of papers presented in 1888 to the Royal Society of London was that the magnificent sunsets enjoyed all over the world for the 5 – year period following 1883, as well as the temperature lows recorded in many countries were the outcome of this explosion.Major volcanic eruptions introduce large quantities of fine volcanic ash and volcanic gases to the stratosphere (sulfur dioxide, carbon dioxide as well as water). Although the largest part of volcanic ash will be removed very rapidly – within a few days or weeks, creating larger particles that precipitate to the troposphere – sulfur dioxide remains in the stratospheric aerosol for longer periods. It then reacts with water and gradually turns into droplets of sulfuric acid. These droplets provoke a more intense reflection of sunlight, thus increasing ‘optical depth’ (i.e. absorbency of light) of the stratospheric aerosol. Sulfuric acid droplets remain in the stratosphere for periods between 3 to 5 years. The eruption of the Pinatubo volcano in Philippines confirmed the above mentioned observations, highlighting the role played by the eruption magnitude and sulfur quantity produced. On June 9, 1991, after 400 years of inactivity, this volcano gave the most severe explosion on Earth in the last 80 years. Nine cubic kilometers of magma were blasted into the atmosphere to a height of 30 km. It is estimated that 17,000 tons of sulfur dioxide were introduced to the stratosphere. Increase of the optical depth of the stratospheric aerosol is five times the respective value prior to the eruption. The volcanic aerosol circumnavigated the whole of the Earth in 22 days; it covered the entire planet in a year. The Northern Hemisphere cooled by 0.5-0.6 degrees; the overall temperature of the planet in 92-93 decreased by 0.4 degrees. The climate change introduced by the Pinatubo eruption has been assessed as more severe than the torching of the Kuwait oil fields during the Gulf War; such an impact is considered equal to a fire blazing in the jungle of the tropics for 6 months. This climate change was more accentuated than the heating effect of El Nino or the man-induced greenhouse effect in 91-93. However it is worth mentioning that the peak sulfur dioxide emissions were a mere 15% of the quantity released by power plants in USA alone. It must be noted that all volcanoes combined produce somewhat more than 1% of carbon dioxide produced by human activities.Another series of measurements following the Pinatubo eruption, that sent a grave warning on the risks from the human-induced disturbance of the atmosphere, refers to ozone depletion measured precisely for the first time beyond uncertainty or dispute. The overall reduction in ambient ozone in 1992-1993 has been estimated to be approximately 2%. Measurements in moderate latitudes within a period of approximately 3-6 months following the eruption in Brazil, Congo and the Island of Ascension, demonstrated that ozone concentration has been reduced by 15-20% at the altitude where maximum concentrations of volcanic aerosols were observed. Furthermore, with regard to the Antarctic ‘ozone hole’, an overall reduction by 10-15% has been noted during the polar spring of 1991. This reduction was partly attributed to the Pinatubo cloud (at altitudes of between 25-30 kilometers) and partly to the cloud generated by the Hudson volcano (at altitudes of between 11-13 kilometers) which erupted in Chile in August of the same year. The basic mechanism used by volcanic gas emissions for the depletion of ozone is a flooding of positions, supplied by minuscule droplets, favoring ‘heterogenous phase chemical reactions’: in other words they allow man-made chlorofluorocarbons (CFCs) to produce, through photolysis, active chlorine that destroys ozone. If CFCs were absent from the stratosphere, then ozone depletion from the volcanic eruptions would be negligible.An attempt to simulate the impact from a major eruption like the one in Pinatubo 10 years later, assuming that the London Pact regarding phasing out CFCs, yielded an ozone reduction by 2.3%. In other words, the impact from a major eruption to the ozone layer in 2010 will be twice as harmful as it would be in 1980.These calculations again demonstrate the delicate balance that is maintained on planet Earth (or the Earth organism, pursuant to the ‘Gaia Theory’ by Lovelock & Margulis (1984)). They highlight our destructive potential as a species, in contrast to our limited functional role, and again set the issue of how ‘recklessly’ we deal with the organism that feeds us. By producing apparently insignificant – compared to the corresponding magnitudes as resulting from nature – CFC quantities, volcanic eruptions may become a hazard for the future of life, instead of an invigorating force for the planet. The conscious mobilization of increasing numbers of citizens against inconsiderate practices and the hope that ‘organism earth’ will manage to readjust once more, retaining its delicate balance and the life that itself created, allow us to be positive for the future and to continue to enjoy the scenery as well as to admire the glory and the magic of volcanic eruptions. |
