How Big Was the Asteroid That Killed the Dinosaurs?

What size asteroid did the dinosaurs collide with? We’ll look at one of the most likely causes for the dinosaurs’ extinction: an asteroid collision, on this page.

A map depicting the location where scientists believe the asteroid impacted Earth may be seen at the bottom of the page.

How Big Was The Asteroid That Killed The Dinosaurs?

Here are the basics if you just want to know how big the asteroid that killed the dinosaurs was: if you’ve landed here, it was about 10 km across.

  • The asteroid believed responsible for the Cretaceous–Paleogene Extinction Event is estimated to have been between 10 and 15 kilometres (6 and 9 miles) across.
  • A common comparison is that the asteroid would have been ‘the size of Manhattan’.
  • Other comparisons are the Martian moon Deimos, which is 12 km (7.5 mi), and Mount Everest, which is around 9 km (5.5 mi).
  • The asteroid would have been travelling at around 20 kilometres (12.5 miles) per second, or 72,000 kilometres / 44,712 miles per hour.
  • The impact would have caused an explosion equivalent to 100 million megatons of TNT (4.2×1023 Joules)
  • For comparison, this is over a billion times the energy of the atomic bombs dropped on Hiroshima and Nagasaki, or around 2 million times more powerful than the most powerful thermonuclear bomb ever tested.
  • The impact would have displaced around 200,000 cubic kilometres (48,000 cubic miles) of sediment.

Let’s now find out more about the asteroid strike theory …

Cretaceous–Paleogene Extinction Event

Scientists have been working to discover what caused these huge, reptilian creatures to go extinct since the discovery that they once walked the Earth.

Palaeontologists determined that no more dinosaur fossils were found beyond a period around 66 to 65 million years ago. So what was behind the sudden disappearance of these people?

The geological time scale is one method used by scientists to date the history of the world. Each geological period is represented by a distinct layer of rock in this system. The sooner a layer of rock was created, the deeper it is discovered.

Palaeontologists realized that the Earth had undergone a global extinction event near the end of the Cretaceous period due to a lack of dinosaur fossils occurring in rocks formed after this epoch.

The Cretaceous–Paleogene (K–Pg) Extinction Event was named after this. Dinosaurs and many other species of animals had vanished abruptly.

How Big Was the Asteroid That Killed the Dinosaurs: The Alvarez Hypothesis

Over the years, many theories as to why dinosaurs went extinct were put forward (including some that suggested an asteroid strike), but none offered a entirely satisfactory explanation.

The Alvarez Hypothesis was then proposed in 1980 by a group of researchers headed by father and son Luis Alvarez and Walter Alvarez.

It was the first to link a probable asteroid impact to geological facts identified throughout the K-Pg boundary, despite the fact that it wasn’t the first theory proposing an asteroid impact.

The K-Pg Boundary

Between Cretaceous and Paleogene rocks, the K–Pg boundary is a narrow strip of rock. Iridium, a rare metal, was discovered to be present in high concentrations by the Alvarez team. Asteroids are one of the rare places in which Iridium may be found in comparable concentrations.

As a result, the Alvarez team believes that a massive asteroid collided with Earth about 65 million years ago. They estimated that the asteroid would have been approximately 10 to 15 kilometers (6 to 9 miles) in diameter, comparable to Manhattan.

A massive cloud of dust would have been flung into the air if such an impact had occurred.

Over time, this would have blocked the sun and prevented plants from growing in the atmosphere. Dinosaurs that ate plants would have been directly affected. Meat-eaters would have perished if they hadn’t had plant-eaters to prey on.

The K–Pg boundary would have formed as the dust cloud gradually settled.

Where Did The Asteroid That Killed The Dinosaurs Hit Earth?


Yukatan, Meksiko

The Chicxulub Crater

It was unknown where the asteroid had impacted the Earth when the Alvarez Hypothesis was proposed.

Glen Penfield, a geophysicist, discovered evidence of a massive crater buried under the Yucatán Peninsula in Mexico around the same time as the Alvarez team was investigating their hypothesis. Chicxulub, the present-day crater’s name comes from, was roughly in the crater’s center.

The crater is roughly 180 kilometers (112 miles) broad and 20 kilometers (12.5 miles) deep. At the K–Pg boundary, it is buried.

Penfold and his colleague Antonio Camargo released their findings together. Scientists didn’t realize until the 1990s that the Alvarez concept perfectly matched the size and age of the Chicxulub Crater.

The Cretaceous–Paleogene Extinction Event was most likely caused by a large asteroid, as shown by the Chicxulub Crater.

How Big Was the Asteroid That Killed the Dinosaurs: Conclusion

The catastrophic extinction of the dinosaurs is the subject of this article, which we hope you’ve enjoyed. It’s incredible that science can reconstruct the events of millions of years ago.

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