It is not yet known how long it took for the dinosaurs, ammonites, etc. to die out, for we still have no means or method for determining so.
Under normal circumstances surface waters are more rich in the carbon isotope number 13 than water in layers below. Therefore, lime skeletons of creatures living on the earth’s surface contain more of this isotope than those living lower, but as the Cretaceous period ended, so did this significant difference. Not until much later did this phenomenon reappear. Scientists can determine only that this difference was formed within a 10,000 year time period. Iridium anomalies also fail to give a more precise figure.
I have discussed in the previous material why impact theory does not explain the late Cretaceous extinctions.
It is possible, that as a result of a cosmic effect around this time iridium levels may have fallen suddenly and drastically. This could be a result of the earth having traversed one or more clouds of dust or meteoric material. Iridium falling off, possibly other materials accompanying it, radiation, or a change in other environmental factors gradually accumulating may have caused the extinction.
(Such death caused by accumulation was triggered, for example, by rising DDT-levels in the case of carnivorous bird eggs. There was a possibly similar case, namely the frequent occurrence of the egg in the egg phenomenon at one of the French dinosaur provenances in the Late Cretaceous. The small animals could not break through the shells of the eggs laid with double walls and therefore died.)
Accumulation may also have had a selective effect. (In the DDT example, the DDT did not destroy insectivorous birds or ticks.)
This process, having lasted for a long period of time, may have enabled certain species to become resistant. (For example, DDT made many insects resistant though not all of them. Another well known example is that of certain, but not all, groups of bacteria having become resistant to antibiotics.)
This theory is not ‘disturbed’ by the fact that there may also have been a (possibly giant) meteor impact around this time, the effects of which would have, at the most, only added.
This theory explains why iridium anomaly has been found all over, since due to iridium’s very low reactivity and its high melting and boiling point even the tiny iridium particles could penetrate through the atmosphere. (Even pure oxygen does not react to iridium when the latter is either heated while dropping quickly or cooler when falling slowly. Iridium does not react to nitrogen either under similar circumstances.)
How large might have been the amount of the additional material reaching the earth?
According to page 132 of the book that I referred to in the previous material the celestial body colliding with the Earth had a diameter of 10 km. The book also stated that its maximum speed reached 5km/s. Therefore it penetrated the atmosphere in about 10 seconds. If this amount of material only had been arriving for one year out of 10,000 years, then the figure is about three ten millionth part per second of it. When converted into the entire surface of the earth, we get a figure of one ten trillionth per second per surface unit. Therefore, this would not have produced any giant dust, heat, fire and smoke as a result of sulfur-dioxide, or tsunami effect. For this reason we do not have to attempt to find an explanation to the controversies discussed in the previous material.
So how large might have been the amount of this material?
The body with an assumed diameter of 10 km had a volume of about 500 km3. Such amount would form about one mm thick layer on the entire surface of the earth. If this amount had fallen down in one year, then it is not large enough to cause unusual effects. This amount equals, for example, the precipitation that would fall in half a day in Hungary.
How could iridium trigger extinctions?
As I wrote before, it was not necessarily the iridium itself, but rather the effect of other materials, radiation, environmental effects all together with the iridium. Iridium itself may have played a significant role though, since while it is hardly oxidizable, it still does form compounds in other ways. (Materials in the sea, especially when taking the long period of time into consideration, might have dissolved iridium and as a result it became much more active). We can not prove iridium’s damaging effect directly in the case of those animals that became extinct 65 million years ago (not even the possible indifference or resistance of certain animals). We only can make assumptions. Such is iridium’s catalytic activity, similarly to other elements of the platinum group, which might have disturbed the vital processes. (That is iridium does participate in the natural vital processes.)
We can see, therefore, that this theory does not have inconsistencies like the ones of the impact theory. It does not assume nearly impossible events. Therefore, it is undoubtedly better. In fact, it may even be true!
Dr. Endre Simonyi