On probable terrestrial nature of the Tunguska explosion in 1908.
G. G. Kochemasov
IGEM RAS, 35 Staromonetny, Moscow 109017, Russia, kochem@igem.ru
Two peculiar characteristics of the Tunguska event (TE), usually not taken into consideration by partisans of the comet- asteroid- meteorite hypotheses, are very important. Firstly, apparitions of anomalous atmospheric phenomena long before the event itself (as though the event has being prepared by growing anomalous state of the atmosphere and was a result - culmination of this state). Secondly, not rectilinear flight trajectory of the shining object. The second peculiarity excludes any relation of the event to a solid body bursting at a great speed from cosmos. An alternative explanation satisfying both "peculiarities" is a giant electrical charge following geopotential lines related to the planetary tectonics and tectonics of the East-Siberian craton. The origin of a giant ball-lightning (GBL) could be provoked by "restless" tectonics accompanied with movements of lithospheric blocks of various dimensions. Friction and pressure of solid blocks are the causes of tribo- and piezoelectricity seeking issues into the atmosphere probably under influence of the electrically charged ionosphere. In any case, some ionospheric events, such as Aurora Borealis, in their distribution are influenced by lithospheric structures.
A directed flight of the formed GBL along the power lines of geofield (not wandering) is the most probable supposition as numerous examples witness directed flights of ball-lightnings along electric wires and geomorphological boundaries. In fact, the Tunguska event occurred within an area of intersection of large weakness zones of the East-Siberian craton superstructure. TE location coincides with a paleovolcano and sulphide showings, has somewhat increased seismicity and is perspective for natural gas accumulations. All theses characterize intersections of large tectonic zones. TE restriction to the peculiar geologic (tectonic) setting is its very important feature rejecting an "accidental fall".
The explosion energy ((1016 J) can roughly constraint the GBL size as density of energy in ball-lightnings is approximately known (1 - 10 J/cm3 , in the Goodlett's case it was 15 kJ/cm3 ). It gives the radius of GBL about 104-105 cm. Ball-lightnings of such dimensions (about 100 m radius) are not registered but could not be rare in scale of thousand years or geologic time.Ъ The estimated size of the GBL body apparently does not contradict to the real size of the Tunguska body as witnesses compared it with the size and shine of the sun disk.
Shining spheres and other formations in air often appear near geological faults, during earthquakes and volcanic explosions. But the Tunguska body is giant. Its uniqueness apparently matches to the tectonic situation of the region occurring within as well unique Tunguska syneclise whereЪ large masses of the Permian- Triassic mantle derived basalts were accumulated. This indicates at great permeability of the fractured by deep faults crust in a particular morphotectonic setting. The area belongs to a planetary scale bend (flexure) of the crust and lithosphere in a place of transition (contact) of the subsided Eurasian sector in the north and west to the uplifted Asian sector in the south and east. The giant flexure of the NE strike, being a part of the great planetary circle marked with large basalt effusions of various ages, goes from the South of Africa to Choukotka. It is well observed in the Earth's relief and planetary geophysical fields. Corresponding to it a wide zone of crushing and faulting is highly seismic.
It is interesting that in this zone also occurs the suddenly ruinedЪ Harappa culture (III thousand years before Christ) in the NW of India. Archaeological excavations indicate a sudden death of people, large-scale fires. The "Mahabharata" epos mentions an "explosion" which caused "dazzling light, a fire without smoke". This anomalous in geologic-geophysical sense huge tectonic "scar" is apparently able to generate though rare (once in several thousand years!) but catastrophic events. With these terrestrial events probably might be compared an intensive flash in 1985 in the vicinity of Proclus crater (Bog of Dream) on the Moon and martian flashes.