Why did dinosaurs and other similar creatures become extinct?

What wiped them all out? Was there a primitive nuclear war or something?

okaybut · 56-60, M

They think it was a meteor. And kind of like a primitive nuclear war.

"The Chicxulub impactor had an estimated diameter of 11–81 kilometers (6.8–50.3 mi), and delivered an estimated energy of 21–921 billion Hiroshima A-bombs (between {\displaystyle 1.3\times 10^{24}}{\displaystyle 1.3\times 10^{24}} and {\displaystyle 5.8\times 10^{25}}{\displaystyle 5.8\times 10^{25}} joules, or 1.3–58 yottajoules).[2] For comparison, this is ~100 million times the energy released by the Tsar Bomba, a thermonuclear device ("H-bomb") that remains the most powerful man-made explosive ever detonated, which released 210 petajoules ({\displaystyle 2.1\times 10^{17}}{\displaystyle 2.1\times 10^{17}} joules, or 50 megatons TNT).[22] The impact created a hole 100 kilometers (62 mi) wide and 30 kilometers (19 mi) deep, leaving a crater mainly under the sea and covered by 600 meters (2,000 ft) of sediment by the 21st century.[23]"

ArishMell · 70-79, M

@okaybut @Crazychick

Was it actually all under a fairly shallow Continental Shelf sea though, or partly on land [i]at the time[/i]? The continents of the world have different shapes and dispositions throughout geological time, as do sea-levels.

The Atlantic Ocean was already well developed by then (it is still widening at about 25mm/yr); and the two American continents were quite widely separated North and South, so the Gulf of Mexico was a very wide channel linking the Pacific and Atlantic.

There is also a theory that by the time of the meteor impact, life was becoming hard for the reptiles due to climatic cooling induced by massive, long-term volcanic activity. The impact greatly worsened that.

By then the early mammals were well established, and able to withstand the changes better than the cold-blooded creatures.

By the way, it should not be imagined that "Dinosaurs" were all the enormous predator brutes lampooned by Hollywood. A few were but the entire range includes many species, both herbivore and carnivore, that were far smaller than [i]Diplodocus[/i]. Also, those species wiped out by the KT_Boundary Mass Extinction were those extant at the time. Dinosaur species had come and gone over tens of millions of years previously.

MySecretIdentity1 · 46-50, M

I don't think there is really a way to know. If they were exotherms, they wouldn't have survived the last ice age. But, if that were true, why are alligators and Komodo dragons still around?