Possible Tectonic Impact of Biosphere

Abstract

16 This paper explores the possibility of existence of ultra-deep biosphere (deeper than 17 10 km under the surface) and the biogenic earthquake hypothesis – the idea that sub18 surface microorganisms might be directly related to earthquake activity. The importance 19 of electroautotrophic type of metabolism is underlined, and the role of telluric currents 20 in this process is explored in some detail, as well as the role of subsurface and atmospheric 21 microorganisms in the global electric circuit. 22 It seems that the existing estimates of the adaptability of biological organisms are 23 inconsistent with empirical evidence, and theoretical concepts predict key biochemical 24 processes to fail long before the onset of the temperatures and pressures, at which mi25 croorganisms are actually observed. This implies that life might exist much deeper be26 neath the surface than previously assumed. At the same time the estimates of energy 27 radiated during the strongest earthquakes are consistent with the biochemical energy avail28 able to the subsurface biosphere. 29 Some additional evidence is examined. It is proposed that the ultra-deep biosphere 30 might represent an important factor in resolving the debate on the nature of hydrocar31 bons. At the same time the deep subsurface microorganisms might play a significant evo32 lutionary role, not only providing seismically induced genetic variation and a ”seed bank” 33 for quick recovery after a mass extinction, but also by modulating longer climatic cy34 cles through planetary-wide bio-geo-electrochemistry. 35 Plain Language Summary 36 The depths of the Earth’s crust and layers beneath it are hostile to living organ37 isms due to high temperatures and pressures. Previous estimates have been suggesting 38 that life (even tiny microorganisms) cannot exist in the Earth’s crust deeper than about 39 10 km. Yet recent findings have shown that the limits of heat and pressure that microor40 ganisms can withstand have been underestimated. It is logical to assume that life can 41 exist at greater depths – up to 75 km at least. 42 The energies produced by microbes under the surface (combined) is enough to pro43 duce an earthquake (shaking of the ground). Perhaps it is this previously unrecognized 44 deep microbial collective that is causing the earthquakes. Earthquakes might release the 45 nutrients and other necessary chemical elements from the surrounding rocks, as well as 46 cause exchange of genes between microbial cells, which might drive their evolution. 47 Most of the earthquakes occur at the edges of the Pacific Ocean at large trenches 48 in the Earth’s crust. These trenches allow microorganisms to get deeper into the crust, 49 where they might produce an earthquake. It might also explain the presence of hydro50 carbons (oil and gas) deep beneath the surface – they might be produced by the same 51 microorganisms. 52