Tollmann's hypothetical bolide

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Alexander Tollmann's bolide, proposed by Kristen-Tollmann and Tollmann (1994), is a hypothesis presented by Austrian geologist Dr. Alexander Tollmann, suggesting that one or several bolides (asteroids or comets) struck the Earth at 7640 BCE (±200), with a much smaller one at 3150 BCE (±200). If true, this hypothesis explains early Holocene extinctions and possibly legends of the Universal Deluge (Kristen-Tollmann and Tollmann 1994).

The positive scientific evidence includes stratigraphic studies of tektites, i.e. Izohk (1988), Glass (1978), and Prasad and Rao (1990), dendrochronology, and ice cores (from Camp Century, Greenland) containing hydrochloric and sulfuric acid (indicating an energetic ocean strike) as well as nitric acids (caused by extreme heating of air).

The 7640 BCE evidence is consistent with the dates of formation of a number of salt flats and lakes still extant in dry areas of North America and Asia, suggesting that the strikes may have occurred in oceans, causing multiple-kilometer-high waves that penetrated deeply into continents, and/or causing large amounts of saltwater to be pushed into orbit and fall down as rain, leaving salt lakes in deserts.

Incursions of salt, sand and oceanic fossils in this period were classically explained by "depression" of continents by the weight of Pleistocene ice, but these explanations are inconsistent with countervailing observations of a 90–120 m rise of ocean levels in the early Holocene. That is, it would be impossible for the sea level to inundate these areas, and then rise 90 m later and remain below them. In some areas (like the Great Salt Lake of Utah), no glacier was present when the salt almost instantly (in stratigraphic terms) replaced a previous fresh-water lake.

Large waves and climatic disruption caused by impacts could have given rise to the stories of global flood found in many cultures, but this must remain speculation.

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[edit] Mainstream evaluation

Quaternary geologists, paleoclimatologists, and planetary geologists specializing in meteorite and comet impacts have rejected the Tollmann bolide hypothesis as proposed by Kristan-Tollmann and Tollmann (1994). They reject his hypothesis because

  1. The evidence used to argue it can more readily be explained by more mundane and less dramatic geologic processes
  2. Many of the events alleged to be associated with this impact occurred at the wrong time, sometime hundreds to thousands of years before or after his hypothesized impacts; and
  3. There is a lack of any credible physical evidence for the cataclysmic environmental devastation and characteristic deposits that kilometer-high tsunamis would have created had they actually occurred.

First, many pieces of evidence used by the Tollmann bolide hypothesis to argue for catastrophic Holocene impacts can be just as well, in most cases even better, explained by more mundane geological processes. For example, the chemical composition of and the presence of volcanic ash with specific acidity spikes in the Greenland ice cores presents clear evidence that they are volcanic, not impact, in origin (Hammer et al. 1980; Zielinski et al. 1994). Also, the largest acidity spikes found in Antarctica ice cores are far too old, from 17,300 to 17,500 BP, to be associated with any Holocene impacts (Hammer et al. 1997). The formation of modern salt lakes and playas ("flats") is readily explained by the concentration of salts and other evaporite minerals by the evaporation of water from stream-fed lakes lacking external outlets, called "endorheic lakes" in arid climates. The composition of the salts and other evaporate minerals found in these lakes is more consistent with their precipitation from dissolved material continually input into the lakes by rivers and streams and concentration by evaporation (Eugster 1980, Hart et al. 2004). Whether a lake becomes salty or not simply depends on whether the lake lacks an outlet and the relative balance between water flowing into the lake and leaving the lake via evaporation. Ocean water dumped into a lake as the result of a single catastrophic event, as suggested above, would contain an inadequate amount of dissolved minerals to produce, when evaporated, the vast quantities of salts and other evaporites found in the salt lakes, playas, and pans cited as evidence of a mega-tsunami by this hypothesis.

In case of Lake Bonneville (Great Salt Lake), the above arguments for the Tollmann Bolide Hypothesis contains factual errors. First, the presence or absence of glaciers does not directly influence whether a lake becomes either a salt lake or not. When the Great Salt Lake was a freshwater lake, Lake Bonneville, a significant source of water was mountain glaciers. It was their disappearance along with reduced precipitation and increased evapotranspiration within watersheds due to higher temperatures that caused a reduction in the freshwater inflow to Lake Bonneville and it becoming a salt lake. Finally, the shift, which started before the hypothesized Tollmann bolide impacts, from a freshwater lake to a salt lake for Lake Bonneville was not instantaneous event, but occurred over a period of several hundred years as discussed in detail by various papers including Spencer et al. (1985) and Hart et al. (2004).

In addition, many published papers, i, e, Peltier (1998, 2002), clearly demonstrate that isostatic depression of the Earth's crust is not only real, but quite capable of submerging substantial portions of coastal areas adjacent to continental ice sheets and resulting in the accumulations of marine sediments and fossils within them. A well-documented example of flooding caused by isostatic depression is the case of Charlotte, The Vermont Whale, a fossil whale found in the deposits of the former Champlain Sea. Like many similar marine deposits, the sediments, which accumulated within the Champlain Sea lack the physical characteristics, i.e. sedimentary structures, interlayering, and textures, that characterize sediments deposited by a mega-tsunami. In addition, many of these deposits and the fossils, which they contain, are far too old, by hundreds to thousands of years, to have been created by impact around either 9,640 BP or 5,150 BP. In case of the Champlain Sea, its sediments started to accumulate around 13,000 BP, almost 3,400 years before the oldest of the hypothesized Holocene bolide impacts.[1]

Second, as noted above, a significant amount of the physical evidence used by Kristan-Tollmann and Tollmann (1994) to argue for Holocene impacts is either too old or too young to have been created by this hypothesized impact. In many cases, it is hundreds to thousands, and in one case hundreds of thousands, of years too old to be credible evidence of a Holocene impact. For example, the research (i.e. Glass (1978), Izokh (1988), and Pasad and Rao (1990)) that dates the tektites, which Tollmann bolide hypothesis regards as indicating the time of the hypothesized impact, is antiquated. Later research, i.e. Schneider et la. (1992), Shoemaker and Uhlherr (1999), and Lee and Wei (2000), has shown the tektites to be far too old, about 790,000 BP in case of the Australasian tektites, to have been associated with any of his hypothesized Holocene impacts. At this time, there exist no documented examples of Holocene tektites. In addition, the formation of salt lakes and playas is neither synchronous nor consistent with the hypothesized impacts having occurred about either 9,640 BP or 5,150 BP. For example, in case of Lake Bonneville, Lake Lahontan, Mono Lake, and other Pleistocene pluvial lakes in the western United States, the transition to salt lakes and playas occurred at different times between 12,000 to 16,000 BP (Benson 2004). Thus, the change from freshwater to salty water and eventually salt playas ("flats") started over 2,400 to 6,400 years before the oldest of the impacts hypothesized by the Tollmann bolide hypothesis occurred. As a result, it impossible that the formation of these salt lakes could have been associated with any hypothesized Holocene impacts.

Finally, credible physical evidence of either multiple-kilometer-high tsunami waves penetrating deeply into continents and the ecological devastation they would have certainly caused have yet to be reported from any of the thousands of paleoenvironmental records constructed from the study of lakes, bogs, mires, and river valleys all over the world by palynologists. In case of North America, many papers, as summarized in Bryant and Holloway (1985), Jacobson et al. (1987), Shuman et al. (2002), Grimm et al. (2004), and many other publications, provide detailed records of paleoenvironmental changes that have occurred throughout the last 10,000 to 15,000 years as reconstructed from pollen and other paleoenvironmental data from over a thousand sites throughout North America. In none of these records, have palynologists recognized any indication of either the catastrophic environmental devastation or layers of tsunami deposits, which the mega-tsunamis postulated by the Tollmann bolide hypothesis would have created. The paleovegetation maps of Shuman et al. (2002) and Overpeck et al. (1992) illustrate a distinct lack of the dramatic changes in North American paleovegetation during the Holocene, which would be expected from the cataclysmic ecological and physical destruction that a continental-wide mega-tsunamis would have certainly have caused.

For example, a 50,000-year long record of environmental change was reconstructed from the analysis of pollen from an 18.5 meter (60.7 ft) long core from Lake Tulane in Highland county, Florida (Grimm et al. 1993). Because of the low-lying nature of the peninsula, which this part of Florida lies, this lake and the area around it certainly would have been flooded and obliterated along with many of the other lakes and bogs discussed by Jacobson et al. (1987) and Grimm et al. (2004). The forests and associated ecosystems of these areas would have been flooded and completely obliterated by the mega-tsunamis proposed by Kristan-Tollmann and Tollmann (1994). Despite its location, both the core and the pollen record as described by Grimm et al. (1993) recovered from Lake Tulane completely lacks any indication of any abrupt, catastrophic environmental disruptions, which the mega-tsunamis proposed by the Tollmann bolide hypothesis would have cause, during the Holocene Stage. This and other cores from Florida and elsewhere also lack sedimentary layers that have the characteristics of sediments deposited by either tsunamis or mega-tsunamis.

The cataclysmic scale of physical and ecological destruction that a mega-tsunamis, like the one proposed by Kristan-Tollmann and Tollmann (1994), would have caused to the Holocene landscape and ecosystems certainly would have left a painfully obvious and readily recognizable signature within the majority of long-term environment records. Such a signature has not been reported from the more than thousand cores from North America for which Holocene paleoclimatic and paleoenvironmental records have been reconstructed. There is a similar lack of evidence for mega-tsunami related, Holocene, catastrophic environmental disruptions and deposits reported from environmental records reconstructed from thousands of locations from all over the world. This lack of a physical record for the occurrence of Holocene mega-tsunamis is quite revealing given that geologists and palynologists have been quite successful in some coastal regions finding in cores and exposures the characteristic sediments deposited by tsunamis locally generated by either earthquakes, volcanic eruptions or submarine slides and recovering abundant well-defined records of their environmental affects of them by studying the pollen from cores and exposures.

A more detailed analysis of the Tolmann bolide hypothesis can found in Deutsch et al. (1994), which was published in the same journal, “Terra Nova”, as Kristan-Tollmann and Tolmann (1994).

[edit] References

Blakeslee, Sandra, Ancient Crash, Epic Wave, New York Times, November 14, 2006.

Benson, L., 2004, Western lakes, in Gillespie, A.R., Porter, S.C., and Atwater, B., eds., p. 185-204. The Quaternary Period in the United States--Developments in Quaternary Science, Amsterdam, Elsevier. ISBN 0-444-51470-8

Bryant, V.M., Jr., and R.G. Holloway, 1985, Pollen Records of Late-Quaternary North American Sediments. Dallas, American Association of Stratigraphic Palynologists. ISBN 0-931871-01-8

Deutsch, A., C. Koeberl, J.D. Blum, B.M. French, B.P. Glass, R. Grieve, P. Horn, E.K. Jessberger, G. Kurat, W.U. Reimold, J. Smit, D. stoffler, and S.R. Taylor, 1994, The impact-flood connection: Does it exist? Terra Nova. 6:644-650.

Eugster, H.P., 1980, Geochemistry of Evaporitic Lacustrine Deposits. Annual Review of Earth and Planetary Sciences. 8:35-63.

Glass, B.P., 1978, Australasian Microtektites and the Stratigraphic Age of the Australites Bulletin of the Geological Society of America. 89(100):1455-1458.

Grimm, E.C. and G.L. Jacobson, Jr., 2004, Late Quaternary vegetation history of the eastern United States. in Gillespie, A.R., S.C. Porter, and B.F. Atwater, eds., pp. 381-402. The Quaternary Period in the United States--Developments in Quaternary Science, Amsterdam, Elsevier. ISBN 0-444-51470-8

Hammer, C.U., H.B. Clausen, and W. Dansgaard, 1980, Greenland ice sheet evidence of post-glacial volcanism and its climatic impact. Nature. 288(5788):230-235.

Hammer, C.U., H.B. Clausen and C. Langway, Jr., 1997, 50,000 years of recorded global volcanism. Climatic Change. 35(1):1-15.

Hart, W.F., J. Quade, D.B. Madsen, D.S. Kaufman, and C.G. Oviatt, 2004, The 87Sr/86Sr ratios of lacustrine carbonates and lake-level history of the Bonneville paleolake system. Geological Society of America Bulletin. 116(9-10):1107-1119.

Izokh, E.P., 1988, "Age-paradox and the Origin of Tektites" in J. Konta, ed., "2nd international conference on natural glasses Abstracts - International Conference on Natural Glasses-Prague, Czechoslovakia, 1988.2: 379-384

Jacobson, G.L., Jr., T. Webb, III, and E.E. Grimm, 1987, "Patterns and rates of vegetational change during the deglaciation of North America". in W. F. Ruddiman and H. E. Wright, Jr., eds., pp. 277-287. North America Adjacent Oceans During the Last Deglaciation. The Geology of North America. K-3. Geological Society of America, Boulder, Colorado.

Kristan-Tollmann, E. and A. Tollmann, 1994, "The youngest big impact on Earth deduced from geological and historical evidence". Terra Nova 6(2):209-217

Lee, M.-Y., and K.-Y. Wei, 2000, "Australasian microtektites in the South China Sea and the West Philippine Sea: Implications for age, size, and location of the impact crater". Meteoritics & Planetary Science 35:1151-1155.

Peltier, W.R. 1998, "Global glacial isostatic adjustment and coastal tectonics" in I. Stewart and C. Vita-Finzi, eds., pp. 1-29. Coastal Tectonics. Special Publication 146:1-29. Geological Society of London, London.

Peltier, W.R., 2002, "Global glacial isostatic adjustment: Palaeogeodetic and space-geodetic tests of the ICE-4G (VM2) model". Journal of Quaternary Science. 17(5-6):491-510.

Prasad, N.S. and P.S. Rao, 1990, "Tektites Far and Wide". Nature. 347(6291):340.

Overpeck, J.T., R.S. Webb, and T. Webb., 1992. "Mapping eastern North American vegetation change over the past 18,000 years: no-analogs and the future". Geology 20(12):1071-1074.

Schneider, D.A., D.V. Kent, G.A. Mello, 1992, "A detailed chronology of the Australasian impact event, the Brunhes-Matuyama geomagnetic polarity reversal, and global climatic change". Earth and Planetary Science Letters 111(2-4):395-405.

Shoemaker E.M., and H.R. Uhlherr, 1999, "Stratigraphic relations of australites in the Port Campbell Embayment, Victoria". Meteoritics & Planetary Science. 34(3):369-384.

Shuman, B., P. Bartlein, N. Logar, P. Newby, T. Webb, III, 2002, "Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet". Quaternary Science Reviews. 21(16-17)1793-1805.

Spencer, R.J., Eugster, H.P., and Jones, B.F., 1985, "Geochemistry of Great Salt Lake, Utah II: Pleistocene-Holocene evolution". Geochimica et Cosmochimica Acta, 49(3):739-747.

Zielinski, G.A., P.A. Mayewski, L.D. Meeker, S. Whitlow, and M.S. Twickler, 1996, "A 110,000 year record of explosive volcanism from the GISP2 (Greenland) ice core". Quaternary Research 45(2):109-118.

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