A sixth fault with the asteroid impact theory is that in most situations the iridium and other noble metals are associated with organic compounds from dead biomass, which is likely to be the source of the metals. The seventh reason is that the abundances of noble metals is more consistent with earthly compositions than extraterrestrial sources at many sites. Also other metals typical of meteoritic materials are missing in some sites with iridium or the ratios are not typical of impact debris. Moreover, the shocked quartz at some sites is more consistent with water transport (ocean erosion) rather than atmospheric (as would occur with impact).
An eighth point is that other times of impact did not cause such extensive mass extinctions. This is apparent in the Barringer Meteor Crater (See Figure 7 for picture) instance in northern Arizona. A ninth outstanding problem is that an impact is theoretically less likely to initiate widespread tectonic activity, and sea level rise, which occurred at the end of the Cretaceous.
A tenth factor is that the climatic shift should have gone from a drastic drop in temperature (with sunlight blocked) to progressively hot temperatures (the Greenhouse Effect). Not withstanding, the temperature went from warm to progressively colder temperature with only a short period with a temperature rise. The atmosphere never rebounded, but was colder than it had been and would remain colder than any time throughout the Cretaceous. In the Cretaceous there was no glacial cover anywhere, and the Arctic regions were much warmer than today with places like Alaska having temperature similar to San Diego, and the treeline and temperate species were much farther north than at present. After the boundary the climate is much more like that of today, with glaciers developing in the following periods.
The eleventh reason is that the mass extinctions of the time do not fit the impact theory for many reasons. One, the extinction were not instantaneous and were selective. Two, many species were in decline before the time of the proposed impact. Three, if the Yucatan region were the impact site then the greatest mass extinctions should be in North America, Central America, and northeastern South America, but were not (it seems that the greatest dinosaur fossil graveyard is in the Gobi Desert, on the other side of the Earth, and most extinctions were along mid-latitudes, not tropics). Four, the huge dust and water vapor cloud should have caused plant extinctions the most, but it did not, and equatorial species should have been hit the worst, but it was mid-latitude species that were affected the most, and most mass extinctions were animals. Five, photosynthetic nannoplankton survived into the Tertiary, and Cretaceous and Tertiary species even coexist in land-based marine sections of the Tertiary. Six, tropical insects should have become extinct, but persist into the Tertiary. And Seven, the dinosaurs appear to have undergone gradual extinction in at least some locations.
The twelfth reason for disagreement with the asteroid impact theory is the high-energy terrestrial explosions, called geoblemes or cryptoexplosions, have not been studied, nor have laboratory simulations been tested. Therefore, much of the evidence for impact is somewhat biased by not considering the evidence in light of all the possibilities. For example, a number or journal articles have shown that the craters on Mars and other planets are dynamically related to the core, and therefore, are internal in origin. Also, the structural similarities of multi-ringed craters with a central peak are too uniform, regardless of size and proposed angle of impact, for them to be impact craters; laboratory experiments show different structures for different angles and impactor size. This suggests that multi-ringed craters with a central peak, like that of the Chicxulub, are internally produced.
The thirteenth reason is that amino acids typical of organic-rich meteor and asteroid remnants were found in Late Cretaceous formations. However, they occur over a long period of time and show no signs of being burnt by entry into the atmosphere, which is not typical of an extraterrestrial source.
The fourteenth, and final argument against the impact theory is that other times of proposed impacts did not cause mass extinctions.
Volcanic Theory
Another main theory, proposed by Officer and Drake which suggests that the K-T mass extinction was the result of hot spot volcanism. (See Figure 8 for representation of a volcano).
The impact theory has been debated with a scenario of huge volcanic eruptions. Like the impact theory, the volcanic event could have brought about drastic weather changes that included a darkened sky, climatic cooling and acid rain. Both iridium and shocked minerals can be caused by volcanic eruptions. Furthermore, the hot lava could cause widespread wildfires.
Near the end of the Cretaceous, India had vast lava flows, known as the Deccan Traps. These lava flows covered an area the size of France. The Deccan Traps were the outcome of the largest volcanic catastrophe since the beginning of the Mesozoic.
Areas in the Pacific Basin, northeastern Asia, Peru, and the Western Interior of North America also had a fairly high level of volcanic eruptions. However, volcanic activity had already been spent by the end of the Cretaceous. Eruptions in Britain, Baffin Island, Canada, and northern and western Greenland began shortly after the end of the Cretaceous.
In some ways the volcanic theory can explain many of the facts that the impact theory cannot. There are a number of iridium peaks with irregular distribution, which can be explained by the fact that the eruptions covered a longer time-span than an impact. It may also account for some of the selective extinctions.
But just as with the impact theory, the volcanic theory has many outstanding problems too. Number one, it is very difficult to reconcile lava flows in India, which was surrounded by seas, with being responsible for global wildfires. This seems especially so when considering that the continents were being pushed and inland seas were either forming or retreating due to major ridge expansion.
Problem number two, basalt lava flows can produce iridium, but none has been found in the Deccan Traps themselves. Furthermore, it is difficult to imagine volcanic eruptions sending iridium globally. The third problem is that shocked quartz can form from violent eruptions, but usually the grains are so large that they do not travel very far. Again, quartz was found at a number of sites.
The fourth outstanding problem is that a volcanic eruption cannot explain the sharp boundaries at some sites. A fifth reason is that some extinctions, such as the global extinction of the dinosaurs, seem impossible to reconcile with just volcanic eruptions.
Number six, the massive climate changes including temperature and ocean perturbations, cannot be accounted for by the volcanic eruptions of the time. And finally the seventh problem is that at least three of the times of massive flood basalts are not connected with mass extinctions.
An extension of this theory known as the Volcano-Greenhouse theory was proposed by Dewey McLean. He proposed that a large volcanic eruption could have filled the atmosphere with carbon dioxide and allowed for a large rise in temperature. According to the theory, the carbon dioxide would have let the suns radiation enter the atmosphere, but not to escape This rise in temperature would have caused some species to become sterile. Infertility could have caused the extinction of the dinosaurs as well as mammals such as the mastodon and the sager-toothed tiger.
A rise in temperature might have killed plankton in the sea, disrupting food chains and making the carbon dioxide factor worse because of its job converting it to oxygen. Without clean air to breath, many animals would die.
The Climate Change Theory
One of the simplest theories of why the dinosaurs became extinct is that the earth’s climate gradually changed. As the continents of the Earth continued to shift 60 million years ago, new mountains rose and sea levels gradually dropped. As a result, the average air temperature around the earth could have fallen 17 degrees or more, changing weather patterns and given rise to new kinds of plants. It’s possible, think some scientists, that dinosaurs were not well adapted to such cool weather. If they were, indeed, cold-blooded animals, then the colder air temperature would have made them more sluggish and less able to hunt or forage for food.
Another possibility is that dinosaurs were not well suited to the new vegetation, such as flowering plants and leafy tree, which thrived in a cooler climate. Convincing as this theory sounds, it does not explain why dinosaurs did not simply move to the tropical regions of the world where the temperature is far warmer, or why dinosaur fossils have been found above what was then the Arctic Circle.
Glaciation, global cooling, and the creation of huge ice-sheets, is perhaps the single most important type of climate change to be implicated in mass extinctions Evidence of these ‘ice-ages’ comes both from characteristic glacial sediments, such as those under the floor of the North Sea, and form the extinction of groups adapted to warm climates.
Glaciation was probably a major factor in a least three mass extinctions, in the late Ordovician, the late Devonian, and the end Permian. It many also have been a factor in the extinction event at the end of the Cambrian period. Another type of climate change, an increase in rainfall, has been suggested as the cause for another extinction, that of the late Triassic.
Climate change causes extinction by altering the type and availability of ecological niches (potential homes for animals and plants), resulting in conditions that are unsuitable for previously thriving species, which must migrate or adapt, they are driven to extinction.
Radiation from a Nearby Supernovae Theory
The suggestion that the dinosaurs were killed off by cosmic radiation from a nearby supernova is pure speculation. (See Figure 9 for an example of a supernova explosion). As no supernova remnant has been, or is ever likely to be, identified, the notion can be neither proved nor disproved. However, it is difficult to explain why certain organisms succumbed to the radiation while others survived. First of all, a supernova would have had to be very close to the Earth for the radiation to have penetrated the atmosphere to a sufficient degree to have completely wiped out all species of dinosaurs. If it had been close enough, and the radiation intense enough, to have also penetrated the ocean (water is a remarkable good radiation screen) to wipe out so many lineages of marine organisms, it should have virtually sterilized the land. Yet a surprising majority of land organisms, from plants and insects to small land and freshwater vertebrates, survived virtually unscathed.
This theory continually reappears because there is evidence of its effects in the fossil record. For example, Upper Cretaceous fossil form Nemegt Valley, Mongolia, had greater radioactivity levels than fossils of upper and lower strata in the same location. Many fossils suggest the effects of radiation, such as mummified dinosaurs, fossilized delicate dinosaur embryos, and pine cones without any signs of predation, decay, or the effects of insects, scavengers or decomposers. Even preserved amino acids may have been discovered, though there is a debate that amino acids could not survive such an extended time period, but if they were buried and the environment irradiated they could survive.
A generally overlooked fact is that mass extinctions are eventually followed by mass speciations, not just during this event, but throughout evolutionary history. Again, this suggests radiation. According to molecular evolution, radiation could split chromosomes, and through the effects of recombination, crossing-over, and aberrations, as well as RNA and DNA mutation, they would be shifted into a different order, hence new species (or in the case of extinction, radiation poisoning or unworkable mutation). Furthermore, research over the past 80 years has shown that nothing is more capable of causing genetic mutation than radiation. This could explain many other facts.
The big problem for the radiation theory is that there is no confirmed source for the radiation. Theories have suggested a nearby supernova (exploding star), a super solar flare, and a super solar flare during a magnetic reversal. However, a supernova would leave behind a molecular cloud (nebula), but none has been detected in a region near Earth. The super solar flare would not cause a major problem as the Earth’s atmosphere and magnetosphere (a magnetic sphere around the Earth resulting from the effects of the geomagnetic field) would deflect the flare. When a super solar flare occurs along with a magnetic reversal, the magnetosphere no longer being protective, the possibility looks promising. However, no known such event has occurred to compare it to.
In August of 1971, an expedition, while in the Gobi Desert, uncovered the skeletons of two dinosaurs still locked in mortal combat. Something very sudden had to overcome them or obviously both would have defended themselves against a common threat. Furthermore, both had their back arched as if something had severely cramped their back muscles. Radiation affects high atomic-number elements more. The most abundant high atomic-number elements in biological organisms are calcium and potassium. These two elements are utilized in muscle function, and ionizing radiation may have caused extreme cramping of their muscles, arching their backs. Some have claimed that the tendons tighten after death producing this arching. Regardless, something had to overcome these dinosaurs very quickly in order for them to still be locked in combat.
Sun Variability Theory
As indicated earlier climate changes is almost always the reason for mass extinctions. It is possible that also the changes in Sun’s (See Figure 10 for a complete diagram of the Sun) activity could be causing some changes in terrestrial climate.
The eleven year solar cycle is the best known variability in the Sun. However, all solar cycles are not equally intense, and it is possible that longer period modulations are operating. For example, long periods of almost no sunspot activity at all have been recorded. Especially the Manuder’s minimum is well known; it is perhaps noteworthy that it coincided with a “small ice age”.
One possible mechanism operating is that during high activity levels that decreased amount to galactic cosmic rays could lead to reduced clouds formation in the atmosphere, and hence to increased temperatures. Some research suggests that the Sun’s variability could account for virtually all of the global warming measured to date. Experts are now scrutinizing three solar variables as likely agents of terrestrial change; the Sun’s overall brightness (See Figure 11 for a picture of the brightness of the Sun), which is seen as affecting temperatures; the Sun’s ultraviolet rays, which are seen as affecting winds and ozone production high in the atmosphere, and the Sun’s storms of magnetic fields and subatomic particles, which are seen as affecting rainfall and the amount of cloud cover.
Just a 1 degree change in the Earth’s temperature can result in mass extinctions.
Magnetic Reversals Theory
The Earth’s magnetic field, like the ozone, acts as a barrier against outside forces. Periodically our Earth’s magnetic field, changes polarity. (See Figure 12 for a timeline of the magnetic field). In terms of magnetic arrangement the poles reverse. Approximately 700,000 years ago, the Earth undertook its last reversal. After a relatively brief stretch of time, the Earth poles shifted to where they are located now. Minerals found in magnetic rocks (See Figure 13 for reversal in rock), when formed, align themselves with the immediate arrangements of the poles. (See Figure 14 for a drawing of the Earth’s magnetic field).
Ozone Depletion Theory
Dr. M.L. Keith, professor of geochemistry at Pennsylvania state University has developed a possible theory for the extinction of dinosaurs. He claims that volcanic gases could have depleted the upper atmospheres protective ozone layer. Base-skinned creatures such as dinosaurs would have been particularly vulnerable to the ultraviolet radiation. Furry mammals, feathered birds, and select sea creatures must have had enough protection to account for their survival.
Galactic Dust
It has been suggested that as our Solar System orbits around the center of the Milky way galaxy, that it might pass occasionally through clouds of unusually thick galactic dust, or clouds of hydrogen gas. Such clouds are known to exist within the galaxy, so the possibility undoubtedly exists. It is further proposed that higher than normal concentrations of dust falling into the Sun might caused it to burn brighter and hotter, thereby increasing the amount of Solar radiation received by the Earth, leading to elevated temperatures and global warming. While all of this is entirely possible, the problem with it as an extinction theory is that there is no evidence to support the ideas that global warming caused, or was even associated with, any of the major extinction episodes.
It is true that temperatures appear to have been universally warmer during the Age of Dinosaurs, so perhaps it was the Sun exiting form a dust could, resulting in global cooling, that caused the K-T extinction. It would have had to be an awfully big dust cloud, however, as the Jurassic and the Cretaceous, nearly 150 million years, both appear to have been warm.