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THE TECTONIC INTERPRETATION
OF THE 1908 TUNGUSKA EVENT

FACTS ARE AGAINST SPACE IMPACT AND POINT TO GEOPHYSICAL ORIGIN!
1. INTRODUCTION AND A LINK TO MY LARGER ARTICLE ON TUNGUSKA

The problem of the nature of the 1908 Tunguska event has already excited researchers over the course of many decades and there is no consensus on Tunguska still (see results of "what was Tunguska" internet poll here).
A 100-th Anniversary celebrations just confirmed that 'Tunguska is still a mystery' (see: http://www.cnn.com/2008/TECH/science/07/04/tunguska.anniversary/index.html ).

In the morning of June 30, 1908, the ground trembled north and northwest of Lake Baikal in Central Siberia, and underground jolts struck panic into the hearts of the local population. Reports of a glowing body flying over came from various points of the territory. The Tunguska forest fall, called the "impact/explosion site" or the "epicenter" was discovered just in 1927 at 61 N & 102 E, i.e. in the northern part of the Tunguska event manifestations region. Various conjectures were soon offered in 1908 to explain the nature of the Tunguska event. The most popular were a meteorite fall, a ball lightning (or its formation) and an earthquake (because of the seismic phenomena). Since official science of the time put in doubt the existence of ball lightning, while the possibility of glow occurring during earthquakes was, as a rule, rejected, and a false report about a meteorite fall near a town of Kansk appeared, the general consensus was that a very large meteorite had come down in Siberia. Attempts to put forward any other interpretations of the Tunguska event had been quashed for many years.

Since that time the situation with the "meteorite fall" Tunguska rather resembles a pendulum: one group of scientists turns up new strong evidences that Tunguska event couldn't have been caused by an asteroid made of stone or iron, thus it had to be caused a comet.
Pretty soon, another group of scientists comes up with new strong arguments that Tunguska could not have been a comet, thus it must have been an asteroid!
The number of supporters of each idea varies with time. The latest maximum for the "asteroid" Tunguska was around 1995. Since then, the attractiveness of an asteroid explanation seems to decline again.
These swings hint that both groups are right and wrong at the same time: Tunguska 1908 was neither an asteroid, nor a comet. But then, what was it?

Many researchers seeing the failure of asteroid/comet interpretation proposed other ideas: a "black hole", an "antimatter bullet", and, of course, UFO (the latter one is, no doubt, the most correct: indeed the event was related with some "unindentified flying object", or sooner with "objects", as it is shown in the link below!).

In late 1980-s I came up with the idea that Tunguska event was something completely different, not a cosmic, but a geophysical event, associated with tectonic processes. My idea, which in the meantime has been presented at several scientific conferences as well as in scientific journals, should not be confused with an earthquake, although earthquakes were indeed associated with the 1908 explosion. It was a more complicated event of tectonic origin in which atmospheric processes played a large role. So probably we can call Tunguska as tectono-atmospheric phenomenon. Now we can just to admit that it was related with some still poorly understood processes of the Earth electricity, but it is just a speculation.
Unfortunately, till now, such phenomena are little known and poorly understood. Moreover, there is no scientific term accepted for the phenomena still. I prefer to call as a "geophysical meteor" or just a "geometeor" (you can read about it here). In a very simplified form often it can be imagined as an explosion of an energetic high-speed ball-lightning.

So this my idea idea (first it was published in IZVESTIA ACADEMY OF SCIENCES OF USSR in 1991, and now it is already rather popular among Tunguska researchers) explains that the 1908 Tunguska event was a manifestation of geophysical (terrestrial) processes, and the most probably, a result a some kind of coupling between tectonic and meteorological processes in very rare combination of favourable geophysical factors.
In general the idea is based on the following:

  • Perusing Tunguska facts shows they don't conform with a stony meteorite or a comet fall. I can add that all known to me computer calculations which claim an "explanation of Tunguska" have large shortcomings, and moreover often contradict to each other.
  • Tunguska event in place and in time coincided with a strong upsurge of tectonic activity on regional and (partly) global levels.
  • There was strong and remarkable coincidence of Tunguska event with particular local and regional (and partly semi-global) meteorological conditions.
  • There were several other remarkable evidences of peculiarities in geophysical situation accompanied Tunguska.

  • Simultaneous realization of all these geophysical phenomena together with Tunguska as just pure accidental coincidence is very unlikely.
    Remarkably, that on small scales similar geophysical micro-Tunguskas occur rather often.
    The exact physical mechanism of Tunguska event is still disputable. In my opinion electromagnetic phenomena play large role in it.

  • You can read my detailed Tunguska story at http://olkhov.narod.ru/tunguska.htm.

    2. MY REPORT ON TUNGUSKA AT THE BRUNEL UNIVERSITY'S CONFERENCE

    Below is a text of my report (see related pictures in http://olkhov.narod.ru/tunguska.htm) at the conference "Environmental Catastrophes and Recovery in the Holocene" (Brunel Univ., Uxbridge, UK, Aug.28-Sept.2, 2002).
    Also below you can read a SCIENCE magazine's note on it.

    THE TUNGUSKA EVENT - THE FACTS ARE AGAINST AN EXTRATERRESTRIAL IMPACT AND POINT TO GEOPHYSICAL ORIGIN
    A.Yu. Ol'khovatov

    Nowadays the situation with so called "Tunguska meteorite" resembles a pendulum: one group of scientists turns up new (and old too) strong evidence that Tunguska couldn't have been an asteroid made of stone or iron, thus it had to be a comet. But pretty soon, another group of scientists comes up with new (and old too) strong arguments that Tunguska could not have been a comet, thus the only way-out is that it must have been an asteroid.
    These swings hint that both groups are right and wrong at the same time: Tunguska 1908 was neither an asteroid, nor a comet.
    And indeed, now I try to demonstrate that it could not have been any known spacebody-fall.

    THE EYEWITNESSES ACCOUNTS

    A main reason to attribute the Tunguska to the fall of a meteorite were reports about flying fiery body. Let's look at these 'flying bodies' carefully from our modern knowledge.
    - Analysis of the most reliable witness's accounts conducted in 1920s and 1930s showed that the Tunguska spacebody flew from the south to the north. But in 1960s a new group of witness's accounts was collected pointing to quite another trajectory: almost from east to west!
    - Even just in a few days-weeks after the event different time was given by different witnesses, from early morning to the afternoon. Conducted in 1980s statistical analysis revealed that the "afternoon" accounts are not at the edge of statistical dispersion, but form a distinct secondary maximum. So was the duration of the event: from a few minutes to an hour.
    - Many witness's accounts hardly conformed to the meteorite fall, as a shape and luminosity of flying object reported in many cases does not resemble a bolide, including such strange as darkening of the sky. And there was no any smoke trail at all!
    - Remarkably that, in the area within 200 km around the epicenter, witnesses did not see any bolide or just even its trail, at least, but they saw flames shooting up, and fire pillars, flashes in the sky and other non-bolide luminosities.

    FOREST FALL

    Here is a map of the famous "butterfly" pattern of the Tunguska forest-fall.

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    PICTURE (omitted here)
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    Now I will try to show that the forest-fall could not be produced by a stony meteorite or by a cometary "explosion". Here are just a few of the arguments:
    - The Tunguska explosion detailed numerical simulation undertaken by Victor Korobeinikov with his co-workers has shown that there must be some additional (internal) source of the "explosion's" energy, and moreover, the source's energy is to be commensurate with spacebody kinetic energy to produce the forest-fall. In plain language, this means that the Tunguska meteorite had to be an enormous block of super-explosive!
    - These calculations also shows that the angle of inclination of the hypothetical spacebody trajectory must be about 40 degrees, while from witness's accounts it must be no more than about 10-15 degrees. The only way-out for the meteorite interpretation is to propose that the angle was changed during its flight because of "non-zero aerodynamic lift", but due to evident reasons avoiding to discuss details of such "guided flight".
    Moreover there are peculiarities of the Tunguska forest fall, which can not be produced by any known type of a spacebody fall:
    - An effect of rotation of fallen trees in the epicentral area. The rotation achieved 5 degrees clockwise in the epicenter, decreasing to negligibly small values at about 16 km from the epicenter. So the field of the mean directions of the tree-fall is the vortex one. In other words, the hypothetical Tunguska spacebody explosion's shock wave was to transfer a very large angular momentum. But such explosion couldn't produce it due to a law of conservation of angular momentum. [Addition of the year 2007: my new detailed research and research of some other Tunguska researchers shows that the rotation (revealed in mid-1960s) could be a computational artefact sooner.]
    - One more puzzle for the spacebody interpretation is the area of the forest fall on the ridge Chuvar, which is about 23 km from the epicenter, and according to the local Evenks had formed the same morning as the general one. The peculiarity of this forest fall is that trees were uprooted with their tops in the opposite of what was expected from the meteorite fall direction.

    THE TREE BURN

    The tree burn in the epicenter is a remarkable and important aspect of the Tunguska event. Indeed some cases of the ignition of wood bedding were reported up to 34 km from the epicenter. So the burn must be many times stronger right in the epicenter, and everything alive would completely burn into ashes at the epicenter.
    In reality many groups of trees survived at the epicenter. Moreover, some single standing trees in open places of the epicenter had no visible traces of the burn!

    GEOCHEMICAL ANOMALIES

    No "Tunguska meteorite" fragments were discovered, despite many years of careful search over vast area. Some minor geochemical anomalies were detected in the epicentral area, but their origin is uncertain. It is important to mention that the isotopic ratio for rare Earth elements in the Tunguska epicenter, which was measured in the place of their most enrichment is a terrestrial ratio. Till now meteorite interpretation has no plausible explanation of the absence of any traces of the spacebody substance.

    SOME OTHER MANIFESTATIONS

    The Tunguska event is also associated with other disturbances and anomalies, as, for example, unusual pattern of seismic manifestations, which also don't conform with the meteorite fall, but unfortunately, I have no time to discuss them.
    But, as we see, the already considered anomalies don't conform with a stony asteroid or a comet fall.

    GEOPHYSICAL CIRCUMSTANCES OF TUNGUSKA EVENT

    In late 1980s I proposed a large role of tectonic and some other geophysical processes in Tunguska event, and began to investigate various geophysical circumstances of Tunguska event, especially its tectonic and meteorological. The investigation brought very interesting data. Here I show that the event took place during a remarkable and rare combination of geophysical factors on regional, and partly, global levels.

    TECTONIC ASPECTS OF THE TUNGUSKA EVENT

    From the geological aspect, the Tunguska event occurred in a rather remarkable place in the southern part of the Siberian platform. It was the place of one of the most powerful volcanic activity in Earth's history 250 millions years ago, a former "hotspot". The area is rich in various gas/oil and ore deposits, including rare earth elements, and platinoids. There are kimberlites in the region too. The upper mantle in this region has anomalous speeds of seismic waves.
    The Tunguska epicenter is right in the middle of the paleovolcano crater. Here the paleovolcano is seen on a satellite picture taken in the near-infrared.

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    PICTURE (omitted here)
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    Also the Tunguska event occurred in the intersection area of several prominent tectonic faults in the region

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    PICTURE (omitted here)
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    It is remarkable, that all main hypothetical Tunguska spacebody trajectories coincide with the most powerful tectonic faults in the region, as well as, the Tunguska event reported luminosities resemble "earthquake lights" very much.
    To check seismic activity in the Tunguska event region, I have investigated a catalog of Baikal-region earthquakes for 1908 and also for near-by years. The result is the following. In 1906 just 1 earthquake to the north of Baikal was registered, in 1907 the number was 2, in 1908 - 6 (including the one associated with Tunguska event), in 1909 - no earthquakes, in 1910 - 1.
    In other words, in 1908 an upsurge of tectonic activity took place in the region of the Tunguska event. Distribution of earthquakes in the Baikal rift region and surroundings inside year 1908 is also remarkable and is shown here.

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    PICTURE (omitted here)
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    So, there was a peak of regional tectonic activity at about the Tunguska date.
    Interestingly, that at about that time an unusual phenomenon was discovered near Ust'-Kut settlement: a hot "salted" spring with various chemical elements, which was absent in previous summer.
    There are also evidences of activation of tectonic processes at the time on larger scales too. The evidences are as follows. I searched through a catalog of the position of the Earth axis of rotation, together with the "momentary" polhode radius of the Earth axis trajectory on the Earth surface (in plain language, the trajectory of the North Pole).

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    PICTURE (omitted here)
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    You can see that between June 14 and July 2 the strongest decrease of the polhode radius has occurred. The rate (per time) of relative change of the polhode's radius for this period was the largest not only in 1908 but also for the whole period of 1907-1910!
    In general, there was a decrease of a total number of earthquake reports in summer 1908, so the seismic energy release that year was one of the lowest for the 20th century. But on another side, on June 30 and July 1 the number of registered earthquakes was increased. It is shown on the picture

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    PICTURE (omitted here)
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    So there are strong evidences of significant activation of tectonic processes in the Tunguska event region, and possibly even of large-scale disturbances in the Earth interior at about the Tunguska date.

    METEOROLOGICAL CIRCUMSTANCES OF TUNGUSKA EVENT

    It is important, that besides tectonic, there were also other numerous geophysical peculiarities in that period of time on regional, as well as, on much larger scale.
    For example, there were some peculiarities in global atmospheric circulation at about the Tunguska date. Cyclones over Siberia in June were much deeper than usual, it led to significant increase of air pressure gradients.
    Another peculiarity was very warm weather in this part Siberia (and even partly in Europe) in the second half of June. Together with the small number of thunderstorms it led to drought in some regions.
    At the beginning of July the situation sharply changed. There was a strong increase in thunderstorm activity. For example in the Perm' province, Russia in July a quantity of precipitation was a record high for the whole 70 previous years of measurements. In the Tunguska event region level of rivers raised leading to floods in some areas. Powerful thunderstorms took place.
    On larger-scale level the Arctic area of high pressure sharply decreased in dimensions.
    I have discovered that in the Tunguska event region a change from good weather to a bad weather was right on June 30, 1908. Here is averaged daily cloudiness data of 9 meteorological stations situated within 1000 km from the Tunguska epicenter (the closest was 500 km away).

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    PICTURE (omitted here)
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    And even more remarkable aspect. Tunguska event occurred exactly at the time of a maximum of atmospheric pressure strong upsurge in the region. In the best way it is seen from the data of the Irkutsk station, which had a log of data with sampling rate every 3 hours.

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    PICTURE (omitted here)
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    Unfortunately, a little is known on the meteorological data at the Tunguska epicenter surroundings. In most places witnesses (Evenks) usually described a clear weather at the time of the Tunguska event, but in some others, they said that weather was not so good, including a sudden rain.
    The closest to the Tunguska epicenter Kezhma meteorological station was 214 km away. Its data at about Tunguska time shows a moderate cloudiness, while 6 hours later it shows the maximum cloudiness.
    In general, statistical analysis of witness accounts conducted in early 1980s has revealed that the Tunguska event was accompanied by various meteorological phenomena, including strong winds (windstorms), haze, fog, temperature changes, thunderstorms, whirlwinds.
    Remarkably, that in late 1920-s, while discussing Tunguska event in Soviet Academy of Science, prominent Soviet meteorologist Prof. Mul'tanovskii B. attracted attention to a possibility of cyclonic air mass movement activation at the area on the date of Tunguska event.

    OTHER GEOPHYSICAL PECULIARITIES

    There are also some other evidences of the peculiar geophysical situation at the time of the Tunguska event. Here I just mention that on June 29 the "Alps Glow" phenomenon was registered in Austria. Remarkably, it was the only registration of this phenomenon for the whole 1908 summer! Also, a Greenland ice layer corresponding to the spring-summer of 1908 contains extremely large quantity of terrestrial dust.

    GEOPHYSICAL INTERPRETATION

    Thus there was a remarkable geophysical situation, including peculiar tectonic and atmospheric activity in the area of the Tunguska event and partly on larger scales.
    Please, pay attention, that if any of the geophysical peculiarities taken separately could be just an accidental coincidence with the Tunguska event, the possibility that they all together were just an accidental coincidence is very unlikely.
    An exact physical mechanism of the Tunguska event is unclear. But on much smaller scales similar events occur from time to time. Unfortunately, I have no time to discuss them in my report. Just a picture. A non-meteoroidal luminous ball fell in Spain in 1994 and produced such a crater.

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    PICTURE (omitted here)
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    Anyway, as we saw, whatever Tunguska was, it could not have been a stony asteroid or a comet fall. Apparently new fresh ideas are needed to invigorate Tunguska research. And also new open-minded researchers, especially Earth scientists, too! There is no doubt that Nature has much more puzzles for us!

    -THE END OF MY REPORT-

    3. SCIENCE MAGAZINE NOTE ON THE GEOPHYSICAL TUNGUSKA

    Below is a note from SCIENCE magazine - a reaction on the above-mentioned discussion of Tunguska at the Brunel Univ. conference (SCIENCE's issue of Sept.13, 2002, p.1803):

    4. WHAT TO READ ABOUT TUNGUSKA?

    There are a lot of info in internet on Tunguska event. It is easy to become enmeshed, especially for a novice. So for those who don't consider themselves as experts in Tunguska, I would like to advise to read a nice popular book "Tunguska fireball" by Surendra Verma (I think that it could be useful for Tunguska experts too). You could read my opinion about the book here.
    When you have got some "Tunguska education" and want to know "every technical detail", I can advise to read about Tunguska those authors, who have some real expertise (experience) in Tunguska research. In my opinion, real data (facts) are the most important in such articles, so a reader can work out his own opinion on "what was Tunguska" basing on the facts, if even authors of the articles have another interpretation. Unfortunately, not many such articles can be found (in open/free access) in internet, especially in English.
    Below are several such articles I would like to advise.

    - The first group of articles is by of TOP 1 researcher of Tunguska - Nikolai Vasil'ev. He was in Tunguska research since 1959 to his death in 2001. Informally he led Tunguska research since 1963 to 2001. He was a brilliant scientist with wide field of view and knowledge.
    Here is his: internet article on Tunguska, and its another version.
    Unfortunately, his most open article was published just in Russian (see here). So I have done its electronic translation into English. Vasil'ev concentrated on discussions of real Tunguska facts/data, and not on groundless speculations.

    - The second group of articles I would like to recommend is a group by researchers from University of Bologna (Italy). Their published results concentrate on search of "remnants of Tunguska spacebody". ...
    Below there are links to articles posted on their www-page: latest research, and early reseach. The authors seem to favour "asteroidal Tunguska". Remarkably that their steady applying of meteorite's interpretation to Tunguska led them to an idea:
    "On the basis of the tree fall data and earlier eyewitness testimonies we consider that the Tunguska Cosmic Body was a multiple bolide formed by at least two bodies of similar mass (see papers pdf, 211 kb, pdf, 18.9 Mb). They likely entered the atmosphere very close to each other following parallel trajectories with azimuths ~135 and an inclination of the total combined shock wave axis between 30 and 50. The first body, with a greater mass, emitted the maximal energy at a height of about 6-8 km. The second, of minor mass, flew a little higher, on the right side and behind the first body, following the azimuth ~135 in the direction of the lake Cheko. " (www-th.bo.infn.it/tunguska/99-NewMap.htm).
    So there must be at least 2 Tunguska spacebodies!...

    - The third group of articles I would like to advise are from well-known Soviet/Russian astronomer Vitalii Bronshten (by the way, he was a nephew of famous communist leader - Lev Trotsky!). Here they are: "The Nature of the Tunguska Meteorite" ( METEORITICS & PLANETARY SCIENCE, vol. 34, no. 5, pp. 723-728 (1999)). and "On the nature of the Tunguska meteorite" ( ASTRONOMY AND ASTROPHYSICS, v.359, p.777-779 (2000) or as Adobe Acrobat pdf-file here). It is interesting to read how Bronshten disputes with the above-mentioned Bologna group, stating that "Tunguska could not have been an asteroid, so it must be a comet".

    - If you are interested in geochemistry, then read this group of articles by Evgenii Kolesnikov with coauthors. Kolesnikov wrote many articles on "discovering Tunguska spacebody substance" since late 1970s. Here is a link to an article by Rasmussen, Kaare L.; Olsen, Hans J. F.; Gwozdz, Raymond; Kolesnikov, Euginev M.: "Evidence for a very high carbon/iridium-ratio in the Tunguska impactor" ( METEORITICS & PLANETARY SCIENCE, vol. 34, no. 6, pp. 891-895 (1999)).
    But their results on composition of the "Tunguska spacebody" are so unusual (if not strange), that it produced some argue: METEORITICS & PLANETARY SCIENCE, v.36, p.999-1006 (2001).

    - Prof. Wolfgang Kundt is in Tunguska research since late 1990s. He is strictly against the "space impact Tunguska", and inclines to think that it was a gas outburst from the Earth interior. Here is one his first articles "The 1908 Tunguska catastrophe: An alternative explanation" ( CURRENT SCIENCE, vol.81, N 4, pp.399-407 (2001)) as Adobe Acrobat pdf-file, or ( the 2003 report.
    Now Prof. J.P. Morgan from the Cornell Univ. joined Kundt with similar idea of so called verneshots.

    And you can discuss all of the above-mentioned at Tunguska-forum: www.topica.com/lists/tunguska/.

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