What do you think happened to the dinosaurs?

Question

What killed them off?

Answer 1

There have been various reasons given for the extinction of the non-avian dinosaurs. There are three explanations given:

1) a meteorite collision;
2) multiple collisions with objects from the Oort cloud
3) climate change due to global cooling.

My view is that 1 is the most likely given that the crate exists and was formed around that time.

Many other groups of animals also became extinct at this time, including ammonites (nautilus-like mollusks), mosasaurs, plesiosaurs, pterosaurs, herbivorous turtles and crocodiles, most birds, and many groups of mammals.

Lets look at the three most likely explanations.

Meteorite

The asteroid collision theory, which was first proposed by Walter Alvarez in the late 1970s, links the extinction event at the end of the Cretaceous period to a bolide impact approximately 65.5 million years ago. Alvarez proposed that a sudden increase in iridium levels, recorded around the world in the period's rock stratum, was direct evidence of the impact. The bulk of the evidence now suggests that a 10 km wide bolide hit in the vicinity of the Yucatán Peninsula, creating the 170 km-wide Chicxulub Crater and triggering the mass extinction. Scientists are not certain whether dinosaurs were thriving or declining before the impact event. Some scientists propose that the meteorite caused a long and unnatural drop in Earth's atmospheric temperature, while others claim that it would have instead created an unusual heat wave.

Although the speed of extinction cannot be deduced from the fossil record alone, various models suggest that the extinction was extremely rapid. The consensus among scientists who support this theory is that the impact caused extinctions both directly (by heat from the meteorite impact) and also indirectly (via a worldwide cooling brought about when matter ejected from the impact crater reflected thermal radiation from the sun).

Multiple collisions - Oort cloud

While similar to Alvarez's impact theory (which involved a single asteroid or comet), this theory proposes that a stream of comets was dislodged from the Oort cloud due to the gravitational disruption caused by a passing star. One or more of these objects then collided with the Earth at approximately the same time, causing the worldwide extinction. As with the impact of a single asteroid, the end result of this comet bombardment would have been a sudden drop in global temperatures, followed by a protracted cool period.

Environment changes

At the peak of the dinosaur era, there were no polar ice caps, and sea levels are estimated to have been from 100 to 250 metres (330 to 820 feet) higher than they are today. The planet's temperature was also much more uniform, with only 25 degrees Celsius separating average polar temperatures from those at the equator. On average, atmospheric temperatures were also much warmer; the poles, for example, were 50 °C warmer than today. This is why I am highly sceptical of current scaremongering on global warming.

The atmosphere's composition during the dinosaur era was vastly different as well. Carbon dioxide levels were up to 12 times higher than today's levels, and oxygen formed 32 to 35 percent of the atmosphere, as compared with 21 percent today. However, by the late Cretaceous, the environment was changing dramatically. Volcanic activity was decreasing, which led to a cooling trend as levels of atmospheric carbon dioxide dropped. Oxygen levels in the atmosphere also started to fluctuate and would ultimately fall considerably. Some scientists hypothesize that climate change, combined with lower oxygen levels, might have led directly to the demise of many species. If the dinosaurs had respiratory systems similar to those commonly found in modern birds, it may have been particularly difficult for them to cope with reduced respiratory efficiency, given the enormous oxygen demands of their very large bodies

Answer 2

I don't think there is a single explanation. I'm guessing that there was some dramatic event that killed off animals near the bottom of the food chain, leaving those higher up the food chain without enough food to eat. Perhaps for them, it was the lack of food plus a major climate change or meteors or something like that.

Answer 3

There have been many theories over this question and one of the most popular reason seems to be that " there was a massive meteorite shower which came & hit the earth's surface and there was a sudden major temperature & climate change which the dinosaurs were too slow to adapt to and thus they eventually perished".

Answer 4

They never died off, they evolved into birds.

More seriously, it was a variety of factors. Certainly the asteroid impact contributed to this, but it was also a period of great change in climate (before hand) and possibly disease. It's a normal part of a cycle of extinction events that have happened in our earth's history. We only think about them so much because they were so big - and there's so much of them left for us to study.

Answer 5

I think a big asteroid fell on earth (such as the one that created a huge crater in Mexico) and the impact of this had disastrous effects.

Answer 6

An Asteroid blew them all up and the climate change had a lot to do with their extinction.

Answer 7

Millions of years of evolution

OR

The BIG asteroid hitting Earth, causing the sky to darken (lacking sunlight). Without sunlight the plants die. Then the plant-eaters die. THen the meateaters die.

Answer 8

I think it was a huge asteroid or comet that slammed into earth, causing a global winter.

Answer 9

as a Born Again Christian, I do believe that it is possible that they vanished in the Great Flood, which wiped everything off of the planet.

Answer 10

A climate change occured in the world and they couldn't survive.