The asteroid that wiped out the dinosaurs

There seems little scientific doubt that dinosaurs became extinct around 65 million years ago due to a huge asteroid that hit the Earth.  

The research that is understood to have settled any major controversies regarding the end of the 'Cretaceous period', a geological term referring to the period in history between 145.5 and 65.5 million years ago, was published in the journal Science in 2010. An international panel of experts from Europe, USA, Mexico, Canada and Japan came to their conclusion on an enormous asteroid, after reviewing 20 years of evidence about what may have caused the end of the Cretaceous period. The end of this period saw the demise of more than half of all species on the planet at the time, including dinosaurs.

Some researchers continue to question the asteroid theory. Although there is sufficient evidence to confirm that an asteroid collided with the Earth all those millions of years ago, some scientists argue that the asteroid could have triggered a series of chain reactions that subsequently led to the mass extinction of dinosaurs, rather than the asteroid itself being the primary culprit. Extinctions do not occur overnight, they are long complex processes that can last for thousands of years.

What do we know about the asteroid that triggered apocalypse on Earth 66 million years ago?

Experts say that the asteroid was around 15 km (about 9 miles) wide and crashed into the Earth at a place that’s now known as Chicxulub, Mexico. According to scientists, in order for an asteroid to create a cataclysmic impact capable of wiping out species on the Earth, it would need to be at least 10km (6 miles) in diameter - that’s roughly the height of a standard passenger plane. 

Earth is actually bombarded with small rock fragments from the wider solar system on a daily basis, but by the time they reach the Earth’s atmosphere they are usually too small to create any serious damage. Scientists do however believe that a similar catastrophe, similar to the asteroid that hit the Earth 65 million years ago, will happen again sooner or later. 

Impact characteristics

If a rock or asteroid fitting the description of the one that hit the Earth 65 million years ago struck our terrain today, it would have (unsurprisingly) devastating consequences. It would would raise sea levels causing a plethora of destructive tsunamis, along with creating enough smoke and dust to form a cloud that would cover the sun for decades, or even centuries. Could you imagine such a scenario?  65 million years ago this unimaginable catastrophe was reality.  

Scientists calculated that the asteroid hit the Earth with a force one billion times greater than the atomic bombs dropped on Hiroshima and Nagasaki. This impact, which left a crater 200 km in diameter, would have thrown material into the atmosphere at high velocity, triggering a series of events that caused a global winter, destroying the majority of life on Earth in a matter of days. The asteroid is also understood to have caused worldwide tsunamis and earthquakes greater than 10 on the Richter scale.

Other speculations: The volcano theory

For many years, some scientists continued to believe that dinosaurs, pterosaurs (flying reptiles) and the other species that were exterminated 65 million years ago was due to a series of volcanic eruptions in present-day India. These eruptions were believed to have lasted approximately 1.5 million years. The eruptions of the Deccan Traps volcanoes (unusually active volcanoes) ejected enough basalt lava to fill the whole of the Black Sea twice. This could have caused a cooling of the Earth’s atmosphere and acid rain on a global scale.

Though this hypothesis differs from the theory of the asteroid hit, it may not be completely to the contrary.  A study published in early 2019 highlights how the asteroid impact in (now) Mexico could have caused 'simultaneous' eruptions on the other side of the world - which would make sense as (now)  India is almost on the opposite side of the world to Mexico.

According to most recent evidence, marine and terrestrial ecosystems were rapidly destroyed in the extinction of the Cretaceous, which does not fit the volcano theory. There is however some evidence that gases emitted during volcanic eruptions after the asteroid hit Earth is what could have caused the global warming that occurred in the final 400,000 years of the Cretaceous.