How big was the dinosaur-meteor

How big was the so-called 'dinosaur-killer' and how big was the crater? Maybe I can get a link to a site who discuss this item.

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Besides the fact that I do not believe that an asteroid killed off the dinosaurs, the one you refer to would be, oh, bigger than a bread basket, but much smaller than Rhode Island.

Hi George,

[snip: disputation across several posts]

Ferns seem to be common enough in Finland, where the temperature can stay well below zero for many weeks each winter.

We have a few hectares of mixed forest at our cottage at 61.5N, and the ground cover includes quite a lot of ferns during summer (ground covered by snow in winter). There are also many ferns in the woodlands near our house at 62.9N. FYI, winter temperatures often dip below -30C in both places.

Best Regards,

As I'm sure you know - lots of people.

No, but many people - as I'm sure you know - think this was a reasonable mitigating factor. You sound rather defensive about your position, so I'm unclear whether you're trying to make a point. Some people don't believe we travelled to the moon, but I think the consensus is that we did - just as the consensus is that a bolide wiped out most of the dinosaur population some 65 mya.

Perhaps you need to look at evoution more closely. Of course - given dinosaurs' extraordinarily long time as a primary inhabitant to the planet - from ~220 mya to 65 mya - most were extinct. But the point is that the existing population of dinosaurs 66 mya were still very numerous. You make it sound like there was a gradual decline over some lengthy but unspecified time, when, at least as I understand it, the dinosaur population was not that different in terms of numbers from say, 170 mya to 70 mya. What differed is the individual species. So what if some species were extinct but others had evolved to take their place? As an analogy, most mammals to have ever existed are extinct also, but mammals are still a large part of the environment.

Not sure if we know, but the fact that crocs are amphibians and dinosaurs are land animals might have been a factor. But either way, you seem to argue against an impact more than 'for' anything specific. What are you advocating here, if anything?

Who cares about irrefutable proof about the exact specifics of size? Generally, 66 mya there was an enormous population of herbivorous and carnivorous dinosaurs of widely varying sizes, up to and including many of the largest to have ever walked the planet. By 64 mya, almost all were gone, and certainly most if not all of the large ones - say bigger than a turkey. Yes, someone might yet find some fossil evidence of some dinosaur as big as a dog, but the trend seems obvious, at least to me. Or are you arguing for the sake of argument (generally known as trolling)?

Ponder it yourself. But if you have anything specific you wish to say, I might try to comment. As an example of why I'm not going to ponder it much, it says more aquatic species would have been killed to to 'global wildfires', for fails to support this 'conclusion'. I'd guess that burning debris falling into the oceans would be relatively benign, given the vastness of the oceans and relative pittance of shorelines with much potential debris. Regards, Brett.

Yes, but there are penty of others who are not easily swayed by irridium isotope signatures.

There is no comparison between the two. There is no concensus on whether an asteroid strike actually caused the extinction of the dinosaurs, despite what you've been led to believe by the popular media. I was around when we landed on the moon, followed the space program very closely, and still do.

Really? and how do you know this? By the huge numbers of fossils found at the K-T boundary? Look again.

Gradual decline, yes. That is proven by the fossil record. How many times does that have to be shown before people get the message? In turns of numbers, and in terms of species diversity, the dinosaurs were in decline up until the K-T event, whatever it was.

Not some, most. The only exception to this, of course, were the theropods, which apparently were thriving, and thrive still today (look out your window at the sky, you might see one fly past).

As an analogy, most mammals to

This is mostly true. Yet the mammalian fauna, though it existed as far back as possibly the Triassic, is largely a Cenozoic phenomenon.

Oh, I thought I was talking to someone who knew something about biology. I guess I was wrong. Hint: Crocodiles are reptiles, not amphibians.

Understand that I am not arguing that an impact did or didn't occur. I am arguing that in the case of dinosaurs, it probably made little difference since they were essentially doomed already. Now, if you want to make a case for the extinction of ammonoids, and many other animals using the asteroid hypothesis, be my guest. The pattern of extinction of dinosaurs is not that different from the pattern of extinctions of many other plants and animals throughout geologic time. Graptolites in the Ordovician, trilobites in the Permian, etc.

Ever since the Alvarez papaer, every time someone sees these extinction patterns it is assumed that something really bad happened. Sometimes it probably did. A very strong case can be made that North American Rhinos (which were never abundant to begin with) became extinct during a massive volcanic eruption in Idaho. A very strong case could also be made that in evolutionary terms, extinction is the rule, not the exception. How many evolutionary 'experiments' went awry before one specially adapted species was strong enough to take hold?

Look at our own fossil record. Why only one species of man today, when tens of thousands of years ago there were at least two, perhaps three? And many more in the past. In geologic terms, man has been in existence for a very short time. And yet, look what has happened to the planet in that short time, as a result of man's actions, and as a result of natural forces. Looking from afar, and perhaps glimpsing our own extinction (perhaps not in the very distant future with the way things are going), one could also argue that some cataclismic event happened on earth because so many species have died during our watch. Well, something cataclismic DID happen. We killed them off with our insatiable greed for property, and our insane need to multiple uncontrollably. No mysterious asteroid need apply.

Sometimes I think we look for a cause for extinctions where there may, in fact be no one specific one at all. The fossil record is very patchy, very incomplete by physical design. Preservation is the exception, not the rule. 95% of all life on earth that has ever lived is extinct. If they were all alive today, do you think the planet would have the carrying capacity to support them? If it survives long enough to breed enough individuals, all life reaches its carrying capacity. Once it reaches its biotic climax, the population will crash. Perhaps we are witnessing this very thing today in many places around the globe. If other external forces such as climate change, volcanism, predator/prey stresses, etc, then act on that population, it can go extinct.

Well, you brought it up, I didn't. Proof is what drives science, not conjecture. You say everything smaller than a turkey died out. Give me proof.

Enormous population? Where is the evidence for that?

This is true. Of that there can be little doubt. Except that there may have been stragglers, as recent evidence in New Mexico suggests.

You've said this before, but you haven't provided any evidence for it. Am I to just take your word for it?

Of course not. I like to be thorough, so as to make as few assumptions as possible. An asteroid hitting the earth, as bad as that would be, does not necessarily translate into the extinction of all dinosaurs. We have no experience as a with this type of event, just as we have no experience with what happens when a Supervolcano erupts.

Wht so defensive? Are you so stuck on this extinction via asteroid hypothesis that you cannot consider what others are saying? Are you saying that their arguments are less valid because you don't believe

How many times will I have to explain this. An impact induced extinction event would result in animals starving to death from lack of plants because the plants have mostly all died from lack of sunlight. The carnivorous animals would aggressively seek out any and all carcasses so the odds of fossilation is actually no better than usual and may be worse since animals seeking food may have left their usual habitats and ventured away from waterways which is where most fossilization occurs.

No, there is evidence from one locality which was becoming increasingly hostile to all large terrestrial animals. Hell's Creek shows a decline in all fossils as the K-T boundary approaches. Since there are fossils of small terrestrial animals earlier in the Hell's Creek formation and they are also missing but it is clear that many of these mammals, birds and reptiles survived K-T what conclusion should be drawn? That the larger terrestrial animals were in decline everywhere but the smaller animals were doing fine or that Hell's Creek was becoming an essentially unihabited region due to quite active vulcanism?

Your insistence on seperate extinction events for the extinctions occuring at the same time requires that you provide some evidence of what caused the seperate extinction events. Since you accept the bolide impact for everything but dinosaurs please indicate what evidence you have seen for the extinction of the dinosaurs.

No, every time scientists see a mass extinction they look to see if some global event can be found to be the cause.

Since humanity's technological culture is a global event it fits in very nicely as the solution to the mass extinction we are presently experiencing.

That is all conjecture and speculation, and not based on the fossil record at all. Its amazing the things gleaned from samples of rock these days.
http://www.sciencedaily.com/releases/2003/01/ 030115065454.htm

The researchers found from the plants that the long, slow cooling that occurred for millions of years of the Late Cretaceous was broken by a warming event that began about 66 million years ago and peaked 300,000 to 100,000 years before the K-T collision. The temperatures then returned to baseline just before the collision and stayed nearly constant before and after the collision. The plant record agreed strongly with the marine data, which comes from ocean coring projects in the South Atlantic, Antarctica and off the shores of New Jersey and Florida, and is based on the oxygen isotope ratios in the skeletons of marine-shelled micropredators called Foraminifera. The colder the water, the more of the heavier oxygen isotope is incorporated in the calcium carbonate of the shells. The sediments that entomb the forams also record the paleomagnetic reversals around the K-T. Because the marine data come from four different locations and the terrestrial data from a fifth, the warming and cooling trends seem global, according to Wilf. The marine data also show that warm water forams migrated from the tropics as far as New Jersey and Antarctica.

While the mean annual temperature in North Dakota today is 43 to 45 degrees Fahrenheit, during the warmest part of the warming episode, the mean annual temperature was from 65 to 68 degrees Fahrenheit. The North Dakota site was then at the same latitude as Quebec City, Canada, and not only palm trees, but alligators and turtles thrived too.

You need to read the paper again. It shows a gradual decline. There is no sharp break for the simple reason that the last dinosaur fossil that shows up in the rock record there indicates that it died at least thousands of years before the k-t boundary. All large terrestrial animals? The crocs seem to have done just fine. And believe me, there were some huge crocs back then.

A thorough a study of non-marine vertebrate fauna across the K-T boundary produced an estimated 36% extinction rate (Archibald and Bryant 1990), which means there was a 64% survival rate. Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years.

Dinosaurs showed greatest diversity in the final 15 million years of the Cretaceous with more than 400 genera present (Russell,1995). Upper Campanian facies in Canada, showed that the dinosaur fauna was diverse with 45 genera present from 13 families. By the upper Maastrichtian diversity had declined, to 24 genera in 12 families (Weishampel 1990) and 30 genera to 7 at the K-T boundary Sloan others(1986).

Bill Clemens (1992) also reported that there was a decrease in diversity from the Campanian to the Maastrichtian , a time period of over 10 Ma, where the number of genera decreased from 32 -19. A barren zone of 3m is present below the boundary where dinosaur bones and teeth become increasingly rare Sloan and others (1986). The last unreworked teeth specimens occurs 60cm below the clay layer (Sheenan and others, 1991). If dating, by the magneto-stratagraphic method Lerbekmo and others (1996) for the final 1m of Cretaceous sedimentation in this area, is correct the 60cm to the boundary could represent a time span of 15,000 years or more.

Bug Creek channels and the Hell's Creek Formation indicate decline of the dinosaurs population. The decline is rapid and increases further nearer the boundary (Williams 1994). Careful and detailed examination of stratagraphic sections at Zumaya, Spain (Ward and others, 1986) and the Hell Creek formation, United States (Sloan and others, 1986) show that extinction had begun well before the K/T boundary layer. Even after accounting for reworking of sediments and mathematical corrections to data sets, to remove the effects of biasing, Archibald and Bryant (1990), still retain that observations cannot be explained by an asteroid impact, but are a result of a geologically rapid, but non-catastrophic extinction causing a loss in range and habitat diversity.

It is clear that dinosaurs declined in diversity over the last several million years of the Cretaceous, of which seems to accelerate towards the boundary, as depicted in North America. However, there is no other evidence for the timing and nature of this extinction in the rest of the world

Well, I guess I tripped over my tongue, didn't I? Thank you for clearing that up.

Neither Iceland nor Norway experience long term extreme cold, both have climates that are tempered by the Gulf stream. Both Canada and large parts of the US experience colder winters than

Read below.

The difference, my friend is that those who are saying that men walked on the moon, myself included, have the life experience to know that it actually happened. That kind of clarity does not exist with regard to the K-T boundary. There are too many unknowns, and uncertainties. You can say that an astreroid impact has been found in the Yukatan that appears to be a candidate for an impact location that occurred at the K-T boundary. You cannot say that that impact, without any doubt, was responsible for anything other than causing a huge hole in the earth. The certainty is not there. With the moon walks, you can, if you so desire, put up the money and go there to see if there are actually footprints, and the equipment left behind, along with the plaques that were left on the moon. You cannot say within any certainty that, based on chemical analysis of the world-wide irridium layer or even the shocked quartz, that the origin of that irridium is the impact crater in the Yukatan. That kind of evidence does not exist.

The fossil record shows a clear decline over time, not a sudden extinction. There is no evidence that that almost all planet life died out at the K-T boundary. In fact, most terrestrial plant species weren't affected at all. I can imagine it all I want, and that won't make it so.

Here is an interesting article for you:
http://www.sciencedaily.com/releases/2003/01/ 030115065454.htm

According to the research describe in the article:

'The researchers found from the plants that the long, slow cooling that occurred for millions of years of the Late Cretaceous was broken by a warming event that began about 66 million years ago and peaked 300,000 to 100,000 years before the K-T collision. The temperatures then returned to baseline just before the collision and stayed nearly constant before and after the collision.'

If the temperature stayed constant before and after the collision, then obviously temperature could not have been a factor in the extinctions.

Interestingly, they conclude:

The K-T impact affected the Earth's living things severely and dramatically [but they don't say how], but the climate changes right before the impact, by comparison, did not,' says Wilf. 'Understanding the climate and vegetation before the impact gives us insight into what kind of world the meteorite struck, and shows us that it was warming, cooling, lushly forested and otherwise functioning the way it always has done. The dinosaurs were well adapted to global warming and cooling, but not to giant speeding rocks from space.'

Ok, fine. They were well adapted to global warming and cooling, so temperature was not a factor, which I agree with. That leads immediately to the question, if temperature was not a factor, what factors about an asteroid strike would cause all of these animals to become extinct? I find it interesting that they would conclude that because the temperature was not a factor in the extinctions, that it had to be an asteroid impact that caused the extinction. In other words, they concluded that because temperature was not a factor, the asteroid strike itself had to be the cause, despite the fact that they make no argument for why an asteroid strike would NOT affect global temperatures, and why, if this was the case, then the obvious conclusion would be that it had to be the asteroid itself that killed them. Excuse me, but that is a huge leap. One conclusion doesn't follow from the other at all.

Evidence from Alberta, Montana and Wyoming suggests that dinosaur diversity started to decline at least seven million years before the end of the Cretaceous. Seventy-six million years ago, thirty families of dinosaurs were living in the region, but by the end of the Cretaceous, only twelve remained. The Red Deer River of Alberta documents the decline even more dramatically. At Dinosaur Provincial Park, the Red Deer River cuts through rocks laid down seventy-six million years ago, when the area was a rich ecosystem where at least thirty-five species of dinosaurs lived. Farther upstream at Drumheller, the dinosaurs and other fossils recovered are less than 70 million years old. Although hundreds of dinosaurs skeletons have been found, only nineteen species of dinosaurs are known to have lived in the region. The rocks become younger to the northwest, where only nine species of dinosaurs seem to have lived in the region sixty-five million years ago. The fossil record along the Red Deer River is one of the best anywhere for the last ten million years of dinosaurian history, and it clearly suggests that dinosaur diversity was dropping dramatically over that period.

At any rate, percentage of extinction figures are for comparison only, and are based on the number of fossil species known. In no way does this actually reflect the actual number of species that might have been extant before or after any extinction event. The vast majority of the 2 million or so species known on Earth today are insects, and over half of those known species are beetles. Insects have been found at least as far back as the Carboniferous Period, yet very few fossil insects are known for any geological period. It can only be assumed that insects were vastly more common than the fossil record would indicate. As insects appear to have been rather resilient to mass extinction events, one must surmise that the actual percentage of species exterminated was greatly lower than the given figures indicate.

Many researchers have argued that the number of different species of dinosaurs diminished considerably during the last 10 million years or so of the Late Cretaceous Period. Whether this represents simply a randomness in the sampling process or a real trend remains hotly debated. This 'randomness of sampling' argument is a serious problem in identifying extinctions, because the mere fact that no fossils of a species have been discovered certainly doesn't prove that it was extinct, particularly with creatures that were as rarely preserved as dinosaurs.

A more convincing statistical argument is based on the relative percentages of each species found within a particular formation. A drastic increase in the abundance of one