By John von Radowitz, Science Correspondent
The dinosaurs might not have been the victims of a giant asteroid after all.
They could have been blown out of existence by an almighty underground explosion with the energy of seven million atom bombs, according to a new theory.
A team of scientists claims the Earth-shaking blast, called a Verneshot, is the best explanation for why the dinosaurs were wiped out 65 million years ago.
Most experts believe the extinction was caused by a huge asteroid or comet that smashed into the Earth off the coast of Mexico.
Others have blamed a mega-volcanic episode, called a continental blood basalt, which resulted in numerous vents pouring poison gas into the atmosphere from a region called the Deccan Traps in India.
But there’s a mystery that neither theory has been able to solve.
The death of the dinosaurs was not the only mass extinction to have occurred since complex life emerged on the Earth 400 million years ago.
In fact there have been four. And each one seems to have coincided both with a continental flood basalt and a meteorite impact, even though the chances of this happening are remote.
The probability of all four extinctions occurring at the same time as an impact and continental flood basalt is one in 3,500.
But according to the new theory from a team of German scientists, a Verneshot could answer the riddle and account for impact evidence such as craters.
The name Verneshot comes from Jules Verne’s book “From the Earth to the Moon” in which a huge cannon shoots astronauts into space.
The theory suggests what might happen if a mantle plume, a stream of lava welling up from deep within the Earth, builds up between a thick chunk of immovable continent called a craton.
If the craton started splitting, or “rifting”, which could occur every 100 million years, the release of pressure would produce a catastrophic gas explosion.
Gases would surge up and burst out at the surface, poisoning the atmosphere and causing severe environmental stress around the world.
The blast would trigger a magnitude 11 earthquake, bigger than any quake ever recorded.
But this would be just a prelude to the main event.
Immediately after the explosion, pressure would plummet in the pipe that carried the gases, causing it to cave in from the bottom upwards.
The collapse would travel up at hypersonic speed, erupting with unimaginable force at the surface and hurling as much as 20 gigatonnes of rock into the stratosphere.
The energy released would be equivalent to 120 billion tonnes of TNT, or seven million of the atom bombs that destroyed Hiroshima at the end of the Second World War.
Debris would rain down from the sky, and dust would blot out the sun to cause the same kind of climate changing effects as an impact from space.
A large piece of rock from a Verneshot blast landing on the Earth would produce a crater in the same way as an asteroid or comet.
An object ejected from the Deccan Traps could explain why the Chicxulub crater, linked to the extinction of the dinosaurs, is so lopsided.
Modellers have concluded that the impactor must have come in from the south-east at an angle of about 20 degrees. That doesn’t rule out a meteorite, but it also fits in with debris flying from the direction of India.
The scientists, led by Jason Phipps Morgan, at the Geomar earth science institute at Kiel University, believe all the impact signatures associated with mass extinctions can be explained by the Verneshot theory,
Deep mantle volcanism, for instance, would bring the rare element iridium to the surface, while the explosion would produce quartz crystals riddled with tiny fractures.
Small blobs of melted rock and carbon particles called fullerines – other hallmarks of a meteorite impact – could also be formed.
Phipps Morgan, whose claims were reported in New Scientist magazine, acknowledges that the theory is very difficult to prove.
The best evidence would be to locate the remains of a Verneshot pipe buried under kilometres of rock. These should show up on seismic images and gravity surveys.
A “circular gravity anomaly” relating to disturbed areas of basaltic rock would be one expected find, says Phipps Morgan.
Though no-one has yet carried out such a survey in detail, large near-circular gravity anomalies have been recorded under the Deccan Traps.
The best clue to a Verneshot event would be to find remains of a projectile inside a crater.
Usually the high-speed approach of a meteorite ensures that it vaporises when it hits the Earth. Verneshot debris, on the other hand, would not travel so fast and should leave some remnants at the crash site.
If rock fragments at the Chicxulub crater were found to originate from the Deccan area of India, it would be strong evidence that the dinosaurs vanished because of a Verneshot.