Tollmann's hypothetical bolide
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Alexander Tollmann's bolide, proposed by Kristan-Tollmann and Tollmann in 1994, is a hypothesis presented by Austrian geologist 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.
The claimed evidence for the event includes stratigraphic studies of tektites, dendrochronology, and ice cores (from Camp Century, Greenland) containing hydrochloric acid and sulfuric acid (indicating an energetic ocean strike) as well as nitric acids (caused by extreme heating of air).
Christopher Knight and Robert Lomas in their book, Uriel's Machine, argue that the 7640 BCE evidence is consistent with the dates of formation of a number of extant salt flats and lakes in dry areas of North America and Asia. They argue that these lakes are the result remains of multiple-kilometer-high waves that penetrated deeply into continents as the result of oceanic strikes that they proposed occurred.
- The evidence offered to support the hypothesis can more readily be explained by more mundane and less dramatic geologic processes
- Many of the events alleged to be associated with this impact occurred at the wrong time (i.e., many of the events occurred hundreds to thousands of years before or after the hypothesized impacts); and
- 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 pedestrian geological processes. For example, the chemical composition of and the presence of volcanic ash with the specific acidity spikes in the Greenland ice cores presents clear evidence that they are volcanic, not impact, in origin. 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. The formation of modern salt lakes and salt 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 consistent with their precipitation from dissolved material continually input into the lakes by rivers and streams and concentration by evaporation instead of evaporation of sea water. 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, flats, 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 contain 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.
Many published papers 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.
As noted above, a significant amount of the physical evidence used by Kristan-Tollmann and Tollmann to argue for this Holocene impact 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 that dates the tektites, which Tollmann bolide hypothesis regards as indicating the time of the hypothesized impact, is antiquated. Later research, 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 salt flats 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 salt flats occurred at different times between 12,000 and 16,000 BP. Thus, the change from freshwater to salty water and eventually salt 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 the impact hypothesized by Kristan-Tollmann and Tollmann.
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, various peer-reviewed publications summarize numerous published scientific papers that 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. Paleovegetation maps 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, E. C. Grimm G. L. Jacobson and others documented a 50,000-year-long record of environmental change by the analysis of pollen from an 18.5 m (61 ft) core from Lake Tulane in Highland county, Florida. 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 described in their and other publications. 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. Despite its location, both the core and the pollen record 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 caused. 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 megatsunami, like the one proposed by Kristan-Tollmann and Tollmann, would have caused to the Holocene landscape and ecosystems certainly would have left an obvious and readily recognizable signature within the majority of long-term environmental 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 effects by studying the pollen from cores and exposures.
Members of the Holocene Impact Working Group have published papers advocating the occurrence of mega-tsunamis created by extraterrestrial impacts at various times during the Holocene and Late Pleistocene. However, none of these proposed impacts match either the cataclysmic scale or timing proposed by Kristan-Tollmann and Tollmann for Alexander Tollmann's bolide.
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- Holocene extinction event
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