Planet Knowledge: The Dinosaurs

Length: 60 minutes (SWR / WDR / BR alpha, 31 Jan. 2003)
Dinosaurs dominated life on Earth for more than 160 million years, only to vanish from our planet over a period that lasted just a few hundred thousand years. And with them, more than half of the animals that existed back then. Why did they become extinct? And why so many species all at once? Many scientists presume that a massive meteorite impact triggered the mass dying. Others tend to believe that a series of devastating volcanic eruptions was the cause.

Dusk for dinos

If one lends credibility to the most well-known theory, the end of the dinosaurs came suddenly. 65 million years ago a meteorite from outer space collided with Earth. When the chunk with a diameter of 10 kilometres smashed into the Earth’s surface, its force of impact was 10,000 times as powerful as when all the nuclear weapons in existence today would explode at once. The meteorite sent soot and dust bursting into the atmosphere. The consequence: The skies darkened, the climate cooled off and the cold-blooded dinosaurs either froze to death or their eggs were unable to incubate any longer due to the colder climate.

The killer meteorite

Remains of the killer meteorite were found on the coast of the Yucatan peninsula in Mexico, although nothing remains to be seen of what was once a 200-kilometre-wide crater because it has been covered by more recent rock strata. That this meteorite changed the world’s climate seems to be proven by the presence of iridium, a metal rarely found on Earth, but often contained in meteorites. Iridium has been found in rock strata around the globe, precisely in the time bordering between the Cretaceous and Tertiary eras.

The mega-volcano

On the other hand, this rare metal could also stem from another source because iridium is expelled by volcanoes, too. This is what the second theory regarding the extinction of dinosaurs assumes, and the theory is gaining more and more supporters among scientists: Prolonged volcanic eruptions hurled incredible amounts of sulphur, carbon dioxide and dust into the atmosphere, thereby assuring global darkness and a drop in temperatures. The site of the mega-volcano: central India. Today the huge Deccan Plateau can be found there. Its volcanic rocks date back exactly 65 million years.

Worldwide mass death

One factor that speaks in favour of the volcano theory is that other known meteorite impacts, for instance in Nördlinger Ries (Bavaria, Germany), did not trigger mass death worldwide. The devastation was merely short-term and limited to a regional area. In contrast, volcanoes could have been a constant source of dust and gases for more than several hundred thousand years. In the end, the dinosaurs did not die suddenly, as would be expected in the case of a meteorite impact, but instead over a lengthy period lasting over 500,000 years: approximately as long as the volcanoes in India remained active. And there are further examples of apocalyptic volcanic eruptions over the course of the Earth’s history: for instance at the end of the Permian period when the huge volcanic plateau in North Siberia arose. That was when the trilobites died out, a precursor to crabs that had practically ruled the seas until then.

Interest in an apocalypse

The reason why the killer meteorite is so popular is probably because the idea is so spectacular. As dinosaurs became trendy, it simply became that much easier to market the catastrophe theory, for example in the dinosaur films from Walt Disney. People’s interest in an apocalypse is a winner, hands down.

Cold-blooded reptiles

When all is said and done, scientists still don’t know why other groups of animals, like mammals, survived the climate catastrophe at the end of the Cretaceous era, but not one single dinosaur. They used to assume that the dinosaurs froze to death because they were cold-blooded. In other words, their body temperature was dependent on the temperature of their environment. In turn, mammals would have survived because they were warm-blooded. Yet these days people know that this presumption is more than questionable. After all, other cold-blooded reptiles survived the Cretaceous era, too. And in Siberia, one of the coldest poles on Earth today, the only living species of vertebrate there is a salamander – definitely not a warm-blooded creature. To top things off, there are also indications that some species of dinosaurs may have been warm-blooded.

People or dinos

This leads to the question: What would have happened if the dinosaurs hadn’t died out 65 million years ago? Dr Michael Maisch, a paleontologist from the University of Tübingen in Germany, postulates that in that case there probably wouldn’t be any human beings today. The reason: “...dinosaurs led the field for more than 100 million years and wouldn’t have let mammals move up the chain.” The scientist’s conclusion: If they hadn’t become extinct, intelligent dinos might possibly rule the world today, not mankind.

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