What theories are there for dinosaur extinction?

Question

:)

Answer 1

The site was so much fun and had so many therories, I just has to copy/paste it.
"http://palaeo.gly.bris.ac.uk/Communication/Couch/possible.html"

High levels of Carbon Dioxide

The release of poisonous substances such as selenium, which could have been fatal, and also thinned the shells of the dinosaur eggs.

ataract blindness. If the dinosaurs couldn't see, there was no way of knowing where they were going or how to find food.

Changes in climate. Changes in the minimum and maximum temperatures could have imposed stresses upon the dinosaurs that they could not adapt to in sufficient time.
Climate too cold, which meant embryo development was inhibited, reducing dinosaur numbers. Furthermore if the dinosaurs were cold blooded, they would not have been able to survive through very harsh winters, as they were too large to hibernate and were unable to keep their body temperature at an appropriate temperature.


Nearby supernova explosion could heat the upper atmosphere, but also disturb the ozone layer and produce large ice clouds in the high atmosphere, ultimately cooling the environment.

Competition with other animals. Much of North America was invaded by Asian mammals, however this explanation is only relevant to a specific part of the world.

Changes in the DNA of dinosaur cells. A variety of genetic mutations could have resulted in weird and wonderful creatures being created, which could not survive.

A metabolic disorder relate to thinning of egg shells during incubation due to variations in certain hormones. The embryos would die, as the shells would be unable to protect them from predation and dehydration. Therefore within a very short space of time all the dinosaurs could have died out if no infants survived.

Increasing Entropy , resulting in less order and the eradication of larger organised life forms.

Epidemics of disease,

Floral Changes. There are numerous related theories, due to the increase and dispersal of angiosperms towards the end of the Cretaceous.

There was a rapid evolution of fungi, especially poisonous species, which may have contributed to the demise of the dinosaurs.

Sudden heating of the atmosphere by the entry of a meteorite.

Wobbling of the galactic plane. If the angle of this plane varies, dust and meteorites can be swept into our Universe, and there are more impact events than usual. There is some evidence that extinction events occur approximately every 26 million years. Wobbling of the galactic plane occurs on a similar frequency, and therefore the two events have been linked together with limited success.

Impact of an asteroid, perhaps the most widely accepted theory at the moment. It is suggested that a meteorite hit the earth at the end of the Cretaceous, causing huge quantities of material to be thrown into the atmosphere, reducing the light, decreasing atmospheric temperature and preventing plants from photosynthesising. Without food herbivores would be unable to survive, and consequently the carnivore dinosaurs would no food to eat, hence their extinction.
For more details try Meteorite Impact

An interstellar dust cloud, effected the atmosphere, by reducing light penetration.

Mental disorders, including a decrease in brain size resulting in stupidity. There is evidence that many of the large dinosaurs, must have had very small brains in comparison to their total body size, possibly as small as a kitten's brain. With such small brain capacity responses to the surrounding environment would have been so slow that they could not compete with faster thinking animals.
An alternative is that there was a lack of consciousness and ability to change behaviour patterns.

The moon was extracted from the Pacific Basin, which would upset the atmosphere and climate.

Changes within the oceans. If ocean sizes and distributions change, therefore habitats are also affected. If the dinosaurs were could not to adapt to these changes, they would have been unable to survive.

Drainage of lakes and swamps, removed important habitats.

Flooding destroyed habitats.

Changes in the distribution of the oceans due to mountain-building.

Spillage of fresh Arctic water into the oceans, resulting in lowered temperatures and changes to weather systems.

Reduction in the area of suitable terrestrial habitats due to increased sea-level.

Transgression caused the bottom of the oceans to become stagnant and lacking oxygen, which is essential for breathing.

Overpopulation, could have resulted in severe competition, rivalry and warfare amongst the dinosaurs. However animal groups also alive at that time, such as birds, somehow managed to avoid such problems.

The effect of parasites, such as lice, worms and flies. They could have overwhelmed the dinosaur population.

Predation from mammals which ate the dinosaur eggs preventing new generations surviving.

Over-predation , especially by the carnosaurs, who overkilled their prey, and hence had nothing to eat.

Overactivity of the pituitary gland, leading to excessive growth of bones and cartilage . This would hinder the movement and efficiency of the dinosaurs.

Alternatively the pituitary glands may have malfunctioned, which lead to overgrowth of frills, horns and spines, and such features impaired their ability to feed and move.

Poisoning by uranium, which was leached form the soil.

Racial old-age and over-specialisation. This includes evidence of enormous size, loss of teeth and spiney growths.

Reversal of the magnetic poles this would have created a temporary failure of the magnetic shield, causing genetic damage and eventual extinction. However there have been numerous reversals of the poles which do not have a corresponding extinction event.

There was a decrease in sexual activity, and not enough dinosaurs were born.

Slipped vertebral discs. This lead to severe back-ache, loss of mobility and the inability to compete for food.

Sunspots, these could have effected the climate and the atmosphere, to the detriment of the dinosaurs.

The explosion of a nearby supernova increased the radiation levels and cosmic ray penetration.

Volcanism. There is evidence that the formation of the Deccan Traps in India, took place at the same time as the dinosaur extinction. Excessive volcanic activity can have significant effects on the climate. The Deccan Traps erupted on a very large scale, and therefore could have had a major impact on the atmosphere at that time. This theory is the main alternative to a meteorite impact, and it can explain many of the associated observations. This includes the shocked quartz and the glassy spherules, see The Impact theory for details of these observations.




Increases in ultraviolet radiation due to destruction of the protective ozone layer by solar flares .

Answer 2

Well, there are (of course) more than three theories, but the three main theories go like this - 1) Meteorite hits the ocean at Chixulub, off the Yucatan Penninsula in Mexico. We do have proof that the meteorite did impact here at the end of the Cretaceous, but the question is whether or not it caused the mass extinctions. The impact would have supposedly thrown up massive clouds of dust that would have blocked out the sun for months, resulting in global darkness and cold, causing plants to die, and dinosaurs along with them. The problem with this theory is that small, ectothermic ("cold-blooded") creatures, such as frogs, would have definately been devastated if this were the case, but the fossil record shows virtually no changes whatsoever in the populations of these organisms. 2) Massive volcanic eruptions in the Deccan Traps, a series of huge volcanoe in what is now India. This event would have spewed enormous quantities of toxic vapors into the atmosphere, and perhaps would also have blacked out sunlight as in the meteorite impact theory. The volcanic theory also encounters some of the problems of the impact theory. 3) I'd say that the third biggest theory is that of disease. Towards the end of the Cretaceous Period, the landmasses known today as Asia and North America had just been joined as a result of continental drift and the oceans receding from record high levels. This would have allowed dinosaurs to travel from these different continents, and bring with them new diseases and sicknesses, which would have spread rapidly throughout the dinosaur populations like wildfire. The problem with this theory is trying to explain other extincions, besides those of the dinosaurs, that occured at the end of the Cretaceous, such as those of marine reptiles. (However, these can perhaps be accredited to climatic change as a result of the world's continents changing.)

Answer 3

Since global warming is the rage now, it is not surprising that idiotic theories have recently be made trying to show that our use of cars will make us go extinct like the dinosaurs. There was a layer of ash rich in Iridium that was found by Alvarez. This layer is likely the remnants of a comet (or comets) that crashed to Earth in the late Cretaceous and killed the dinosaurs. One very huge problem with this theory is that dinosaurs were already showing big problems before the layer. The number of species became much fewer. It is possible that a land mass connected resulting in the invasion of many species that outcompeted the existing forms. They carried with them disease (migrating both ways). This caused a reduction in the number and then pow the asteroid hit (perhaps) and wiped them out. In addition flowering plants and grasses became common and certain mammals were adapted to eat these. It may very well be a number of factors but the truth is we still don't know.

Answer 4

I like "icabod";s answer. He even mentioned an associated event, the Deccan trap volcanism in what we call modern India, a situation (condition) scientists are apparently beginning to include with the meteor event as possibly the event that exacerbated the meteor impact and finished off the dinosaurs and much of all the life then on the planet.

Of course, somehow, little scurrying pretty much anything eating shrew-like mamals managed to survive and that ain't bad for the current dominate life form on the planet.

It appears to be probable that the Chicxulub ( I assume the name is Mayan) meteor is responsible for you and I not being some advanced reptilian life form!

kudos to 'icabod' for his fine research!

Answer 5

About 99% of the world population cannot, or more accuratily, will not accept the truth. It is a forgein thing to them which they believe is too old fashion to be accepted. The simple truth is there was a world wide flood that wiped them out. Thats why they are found all mixed together in the same places. Animals that ate other animals were buried together in the run off. Silly....Huh?

Answer 6

Around 62.5 million years ago, a meteorite inpacted the Earth, in the Gulf of Yucatan, leaving a layer of Osmium, and other rare elements, in the rock strata, all over the world. Just above that layer (occuring later in time), no more large fossilised dinosaur bones are found. Elementary, my dear Watson.

Answer 7

A meteorite crashed into the earth.
That theory is the most trusted by modern scientists.

Answer 8

the latest one is that the gulf stream was interrupted,thus all the oxygen releasing lifeforms in the sea died off and most animals died from lack of oxygen.Once the gulfstream started up again it was too late for the dinosaurs.

Answer 9

The cavemen left their kids to feed them.

Answer 10

the one currently at the fore front is meteor impact leading to a nuclear type winter