the mass extintion theory about the comet or asteroid killing the dinosaurs has fallen into question why?

Answer 1

I did not know of this.

I was aware of the debate surrounding the fires after the asteroid hit earth. The link I have attached is a BBC one discussing that very same thing.

I recently watched a science programme which showed research that clearly indicated that the dinosaurs due to the initial impact, associated fire and the ash debris that covered the earth blocking plant life.

The reasons for argument had been focussed on rocks that did not show effects of fire (charcoal). The programme I saw (which I have forgotten) showed an experiment where the angle of the asteroid at 30 degrees created an effect that they could substantiate with rock findings. Whereas initial studies surmised a direct hit with equalised spread of damage which the geologists could not support in findings.

To add to the argument found a great Q&A site regarding the differing academic views - it is still under debate!

What did scientists think killed the dinosaurs before the impact theory was put forward?
Before the late 1970s, there were any number of different theories to explain the mass extinction, with no real consensus. One theory put it that mammals had eaten all the dinosaurs' eggs, but this has now been largely discredited. Another, much more widely supported, theory was that massive volcanism caused environmental changes which drove the dinosaurs to extinction. Walter and Louis Alvarez first proposed the impact theory in 1979. Soon it would dominate all thinking on the subject.

What is iridium? Does it occur naturally on the Earth?
Iridium is an element which is found on Earth, mostly in the molten mantle, the layer beneath the crust. Sometimes it is ejected in volcanic eruptions, but it's still extremely rare. It is found in far higher concentrations in some kinds of asteroids. The impact theory was first put forward when scientists discovered asteroid-type concentrations of iridium in the KT boundary layers.

How do scientists explain the survival of some groups of animals during and after the impact?
It depends on who you ask. Some supporters of the impact theory suggest animals like frogs, turtles, crocodiles and fish survived by immersion in water or mud. This immersion, they argue, protected them from the initial heat wave and from the subsequent cold of an 'impact winter', when dust and atmospheric chemicals blocked out the sun.

Mammal species also survived. The theory has it that because most of them were small they could burrow to escape the heat and the cold.

Those who oppose the impact theory argue that the very survival of these kinds of animals, some very sensitive to cold and pollution, undermines the idea that there was a global environmental catastrophe at all.

How likely is that two massive asteroids could have hit the earth within 300,000 years of each other as Prof Keller suggests?
There is evidence that impacts might come in clusters, caused by a lot of debris flying around the solar system at particular times. For example, two huge craters from about 35 million years ago were created about 200,000 years apart: Popigai crater in Russia and Chesapeake Bay crater in the USA. So although it would be unusual, it's certainly not impossible that there were two big impacts at the KT boundary.

How likely is that Prof Keller's team will find a crater from the second impact that they say coincided with the end of the dinosaurs?
It is possible but perhaps not likely. 70% of the Earth's crust has been 'subducted' - pushed back into the mantle by another tectonic plate - over the last 65 million years. Of course, supporters of the single impact theory argue it will never be found, since it doesn't exist!

Why do Keller's team believe that another impact caused the extinction? Why don't they think it could have been something else?
They believe that there were two impacts, one at Chicxulub 300,000 years before the final disappearance of the dinosaurs, and another which coincides with the 'KT boundary', the rock layer which most believe marks the dinosaurs' demise.

But they do not believe either impact was primarily responsible for the mass extinction. Instead, they argue that a combination of factors such as massive volcanic activity in western India and global warming were also responsible.

What other reasons are there for doubting the impact theory?
One addition to the impact theory was that returning molten debris set forests ablaze all over the planet. But Claire Belcher of Royal Holloway, University of London has shown that it is very unlikely that there were such wildfires beyond about 2,000 kilometres from Chicxulub. This does not suggest that there was no impact, only that its effects were not as calamitous as once assumed.

Where does the debate stand now?
There are still several broad schools of thought. The dominant school is still without doubt the impact theory, which the majority of earth scientists support.

There is another long standing tradition which stresses the importance of the volcanic Deccan Traps in western India. This had been active for several hundred thousand years before the impact(s) and, it is argued, caused a variety of dramatic climatic changes which caused the mass extinction.

The third school - which many palaeontologists have always favoured - is that global warming and the disappearance of habitat were responsible. In the half million years before the impact a massive inland sea which had covered much of North America disappeared, taking with it the coastal plain habitat on which it is thought the dinosaurs depended.

Others still believe that all of these schools are valid, and that the dinosaurs were killed off by a lethal combination of circumstances.

But isn't it obvious that the dinosaurs were killed by the asteroid, because they died out just when the asteroid hit?
This again is a matter of controversy, and scientists cannot agree on how to interpret the fossil record.

Dinosaur fossils are relatively rare, and complete specimens rarer still. This means that in comparison with other more populous animals it is very hard to tell exactly when the dinosaurs became extinct.

Some palaeontologists however do argue that the record shows they were annihilated by a sudden event. Others maintain that the dinosaur fossil record cannot support this idea, and that it is likely they were dying out (along with many other creatures with better fossil records) for millions of years before the impact(s). We know that after the asteroid hit there weren't any dinosaurs, but it's possible a lot of them died out earlier than that.

http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dino_qa.shtml

Answer 2

Two reasons.

First, dinosaurs were apparently dying out before the collision (marked by the iridium anomaly at the KT boundary 65 million years ago). Dino fossils have also been discovered in the sediments above this layer, suggesting the meteorite collision didn't instantly finish them off.

The second reason is that another hypothesis has gained ground in recent years. The Deccan Traps in India are the site of a a massive outpouring of lava (flood basalt) at about 65 million years ago. It is thought that the massive outpouring of material and volatiles into the atmosphere may have caused a nuclear winter that killed off the cold-blooded dinosaurs.

Only more research will help us to constrain arguments for or against the meteorite extinction model.

Answer 3

"How can the "asteroid killed the dinosaurs" concept have income?" It has to do with the obtainable info. ". yet in the impact web site (and quickly round) of the position this asteroid befell there is not any longer been a unmarried dinosaur fossil got here upon at the same time as there should be tens of millions of useless animals there." because the impact web site (and quickly round) takes position to be in the sea, the lack of dinosaur fossils there is not any longer extraordinarily astounding, and by no skill purely using impact. tens of millions of useless land animals are not in all probability to be less than the sea on the time, and the circumstances brought about through a collosal impact are not precisely perfect for fossilization. "Then they say that the animals international huge were laid low with really boiling alive from the meteor showers starting to be intense warmth how does that designate how deep sea creatures went extinct yet a crocodile who lives on the exterior (frequently, or very on the brink of it) survived?" Calculations recommend person-friendly broiling extremely than boiling, and being somewhat less than the exterior for a marginally short at the same time as is in all probability to have presented protection sufficient. it is also no longer unavoidably so as that each and each one the extinction experience(s) were delivered about through an same reason or motives. extremely than being boiled to lack of existence, plesiosaurs and mosasaurs would were killed off for different motives; eg. the cave in of nutrients platforms. "i'm only curious how this may have income at the same time as crocodiles should not be alive in accordance to that concept." That become in accordance to you, no longer theories about the metorite impact. replace "incorrect - the meteor brought about a good number of textile in the ambience that cooled the Earth and disrupted the nutrients chain..." no longer incorrect! interior of an afternoon or so of the impact, a good number of dirt and debris would were returning through the ambience and burning up. that would want to nicely have brought some global grilling. in the intervening time, different debris remained in orbit, and that would want to nicely have later brought about cooling. First a bang, then warming, and thereafter cooling.

Answer 4

Because fossil record shows dinosaurs populations were on decay approximately 1 mill yr before the actual impact, suggesting a decay in the number of species due (maybe) to climatic changes, vulcanism, epidemics, etc.
More research has to be done to clarify this particular event.

Answer 5

I think an alternate, more plausible theory is that mammals (rodents specifically) came along and decided that dinosaur eggs are good eatin'.
NOT Mankind. We came along much later.

Answer 6

i didn't know it had....but it has been proven that the asteroid did impact earth and that the dinosaurs did die out at about the same time.....

Answer 7

i didnt know it had, never try to start an argument with a supposition, its rude and bad grammer.

Answer 8

people who believe the bible word for mistranslated word have always and will always question truth.... no matter what proof is found....

Answer 9

pogonoforo's answer is right on!!!!!!!!