Not everyone thinks the Carolina Bays were created at the time of the Little Dryas impact event. Not everyone even thinks they are impact features.
A number of different researchers get dates for the Carolina Bays inconsistent with the 12,900 BP time of the Younger Dryas. One of these is Paul Heinrich, whose paper An Evaluation of the Geological Evidence Presented By ''Gateway to Atlantis'' for Terminal Pleistocene Catastrophe, challenges the connection of the Carolina Bays with the Younger Dryas climatic event, was published in December 2007. In spite of the reference to Atlantis in the title, the article seems to be well written and well documented. This is his conclusion.
In a detailed examination of the geologic evidence offered by Collins (2000a) for a catastrophic meteorite or comet impact about 10,500-10,600 BP (8,500-8.600 BC), I found that none of the observations or data provide convincing evidence for such an event. In the case of the Carolina Bays, there is overwhelming evidence that these features formed tens of thousands of years before 10,500-10,600 BP. Thus it is impossible that these features could have been formed at the time proposed by Collins (2000a). Also there exists a lack of any credible evidence indicating that some sort of impact related process produced them given that their morphology has been modified by tens of thousands of years of lacustrine and eolian processes. The deep sea craters cited by Collins (2000a) as evidence lack any convincing evidence of either their formation or existence to the point of being imaginary features. Similarly, the catastrophic interpretations of the so-called Alaskan muck by Hibben (1942, 1946) represent antiquated and obsolete research that has been complete refuted by research published in the decades since his papers and book were published. What is now known about the character and chronology of Mississippi River and global meltwater pulses contradicts Collins (2000a) interpretations to the point of refuting them. In fact the timing of meltwater pulses show that the transition from glacial to post-glacial climates started thousands of years before the date of his proposed impact and impossible to have been the result of it. Although rapid periods of synchronous warming have occurred during the transition from glacial to post-glacial climates, they were common features of paleoclimate during the last 125,000 years. They were far too common to be explained by invoking relatively rare large-magnitude comet or meteorite impact. The timing of these events is inconsistent with a meteorite or comet impact about 10,500-10,600 BP. Furthermore, as does the data on meltwater pulses, palynologic and other paleoclimatic evidence clearly demonstrates that the transition from glacial to post-glacial climates started thousands of years before 10,500-10,600 BP. In summary, none of the examined geologic evidence provided any evidence for the cosmic catastrophe provided postulated by Collins (2000a). When the latest research was examined, it directly contradicts his ideas concerning a terminal Pleistocene catastrophic impact.
Andrew H. Ivester, in a paper delivered in October 2002, Carolina Bays and Inland Dunes of the Southern Atlantic Coastal Plain Yield New Evidence for Regional Paleoclimate, comments on the dating problem and concludes the Carolina Bays were formed by the wind. Many of the bays overlap, which makes an aeolian origin very difficult. I found three other similar papers written by Ivester in November 2003, November 2004, and March 2007. This is the abstract of his 2002 paper.
New optically stimulated luminescence ages from eolian landforms in the Coastal Plain of South Carolina document multiple episodes of inland dune and Carolina bay development. Ages from eolian sand rims on the southeast edges of Carolina bay wetlands indicate conditions were suitable for rim development—i.e., southwesterly winds were blowing across ponded water—during several intervals of the late Quaternary. In the upper Coastal Plain, dates from Flamingo Bay indicate the rim was active at 108.7 ± 10.9 ka BP and again at 40.3 ± 4.0 ka BP. The nearby Bay-40 had an actively forming sand rim at 77.9 ± 7.6 ka BP. Near the confluence of the Wateree and Congaree Rivers in the middle Coastal Plain, an eolian sand sheet was dated to 74.3 ± 7.1 ka BP. The surface of the sand sheet has been reworked to produce smaller-scale parabolic dunes, two of which were dated to 29.6 ± 2.4 ka BP and 33.2 ± 2.8 ka BP. Five dates from dunes on Sandy Island, between the Waccamaw and Great Pee Dee Rivers in the lower Coastal Plain, fall in the general range of 30 to 40 ka BP. These new ages, combined with previously reported dates from dunes and a bay rim in Georgia, are beginning to clarify the late Quaternary environmental history of the southeastern Coastal Plain.
Henry Savage gave this rebuttal to the aeolian hypothesis in his 1982 book "The Mysterious Carolina Bays".
That Kacrowski, the current leader of the wind theorists, found it necessary to journey all but literally to the ends of the earth to view features on harsh landscapes in fierce climes that only faintly resemble Carolina Bays speaks for the uniqueness of the Carolina Bay phenomena, particularly when the striking images brought back from those places are contrasted with Carolina Bays. Even more pertinent questions confronting the wind origin theorists are nearer at hand. How, for example can they account for regional winds being so much more emphatic in their earth sculpturing activities in the border region of the Carolinas than elsewhere in the region? How can they with credibility attribute to winds, notoriously symbolic of instability and vagaries, the creation of beautifully sculptured, almost perfectly elliptical overlapping Bays without semblance of distortion of either? If they are familiar with the tenacity of the root bound earth of Southern ponds, how can they reasonable espouse a wind genesis of the Bays in the face of the knowledge imparted to us by those pollen studies of the paleobotanists.
The wind isn't the only alternate explanation for the Carolina Bays. James H. May and Andrew G. Warne of the U. S. Army Waterways Experiment Station, Vicksburg, MS, in an August 1999 article in Environmental and Engineering Geoscience, Hydrogeologic and geochemical factors required for the development of Carolina Bays along the Atlantic and Gulf of Mexico, coastal plain, USA, say the Carolina Bays developed "as silica-karst features". Here is the abstract of their paper.
More than 60 years of intense study and debate have yet to resolve the origin of the Carolina Bays. Carolina Bays are circular to elliptical depressions located along the Gulf of Mexico and Atlantic Coastal Plains. Proposed processes of initiation and development of these karst-like features include meteorite impacts, substrate dissolution, wind, ice, marine waves and currents. Based on field studies throughout the Atlantic and Gulf Coastal Plains and on review of coastal plain literature, we propose that Carolina Bays initially developed as silica-karst features. During Pleistocene sea-level lowstands, water tables in the Atlantic Coastal Plain were up to 30 m lower than today. Large volumes of surface water collected in local topographic lows and/or areas of enhanced permeability and infiltrated through sandy substrates of the low-relief coastal plain. Localized infiltration of phreatic water induced extensive desilicification of the sandy and clayey substrates, resulting in volume loss and development of karst-like depressions. Particularly relevant to initial bay development was alteration of kaolinite to gibbsite, which can produce a 34-percent loss in clay material volume, and concurrent dissolution of iron oxide. The initial silica-karst depressions along the Atlantic and Gulf coasts were later modified by eolian and, perhaps, ice-push processes, which enhanced their elliptical form. The subsequent Holocene rise in sea level caused ground-water levels in the coastal plain to equilibrate near the present-day land surface. This curtailed geochemical weathering, as well as eolian and ice-related processes. Ground-water saturation partially reversed chemical reactions associated with intensive weathering of clays beneath the bays, masking evidence of the severe leaching that occurred during their initial formation. Silica-karst features, similar to Carolina Bays in their initial stages of development, are common geologic features. Moreover, silica-karst processes are active today in warm temperate, subtropical, and tropical areas in sandy substrates where ground-water levels are well below the ground surface and can cause subsidence or disrupt developing wetlands.
Richard B. Firestone, whose work we've already read about, and William Topping, coauthored Terrestrial Evidence of a Nuclear Catastrophe in Paleoindian Times presenting their theory that (even if an impact event didn't do it) a nearby supernova might be responsible for the 12,900 BP extinction event and the Carolina Bays.
As a humorous note in closing, there is even one researcher who believes the bays are the result of the activity of beavers.
I rather like the concept of the Younger Dryas impact event, and I think the evidence that something dramatic happened in 12,900 BP is substantial.
What is your theory?
Extraterrestrial Impact Energy
How much energy is released when the earth gets in the way of an asteroid or a comet? How is it calculated?
An object falling to earth from an infinite height strikes the earth (neglecting air friction) at a velocity of 11.186 km/sec. This is called the escape velocity, because an object fired into space from earth has to have at least this velocity relative to earth or else gravity will cause it to fall back to earth like everything else we throw up into the air. The earth’s orbital velocity is 29.79 km/sec. A stationary object meeting earth head on would be traveling at the sum of these two speeds when it landed ~ 41 km/sec. Since objects are never stationary, but are traveling around the sun in their own elliptical, parabolic, or hyperbolic orbits, the impact velocity can be significantly more or less than this amount. I will assume 41 km/sec in my estimates of comet impact energy.
When a meteor (or something larger) is slowed down by passage through the atmosphere, or by impact with the earth, its energy of motion is converted to heat. The material of the object absorbs some of that heat and is vaporized. The atmosphere and the earth absorb the rest. [Objects below a certain size are vaporized completely before reaching the ground. Most of the “shooting stars” we see at night are the size of a grain of sand, and are visible between 60 and 120 km above the ground.] The heated materials expand violently, and there is an explosion.
We usually describe the energy released in an explosion in terms of the equivalent amount of TNT (trinitrotoluene) needed to give the same sized bang. Energy is measured in Joules or Ergs. The following statistics are from the 1992 McGraw-Hill Encyclopedia of Science and Technology.
A moving body has “kinetic” energy. To calculate the kinetic energy of a comet or asteroid, we need to know its mass and velocity. It is always necessary to keep the units consistent. You can’t mix meters and inches, or pounds and kilograms. We'll be using the "cgs" units of centimeters, grams, and seconds.
According to a study of comet Shoemaker-Levy 9’s impact with Jupiter by Johndale C. Solem, the density of comets is about 0.5 g/cm3. That's consistent with the belief that comets are fluffy snowballs.
Let's assume a comet half a kilometer in diameter (50,000 cm) traveling 41 km/sec (4,100,000 cm/sec) relative to earth.
If you divide this result by the number of ergs per megaton of TNT, you get 6,600 megatons. That's a BIG explosion. To put this in perspective, the US had a total of about 2,500 MT at the end of 1991, before START I. The Soviet Union had about 4,500 MT. If a comet this size struck the earth you'd be dead, but at least you wouldn't be radioactive. Holy Nuclear Winter, Batman!
And on that happy note I'll end this series on the Younger Dryas impact event.
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