Gigantic tsunami wiped out the dinosaurs

A global tsunami with kilometer-high waves, and a gigantic earthquake that didn’t end until several months later.

When Earth collided with an asteroid 66 million years ago, an abyss opened up for the dinosaurs and other life forms. The inferno can now be described in new details by the researchers.

It is now accepted that the collision was the direct cause of the extinction of the dinosaurs. They had roamed the Earth’s surface for 135 million years, throughout the Jurassic and Cretaceous periods, but were apparently out of luck when the alien celestial body struck. In total, 75 percent of the earth’s animal and plant species were wiped out.

The asteroid was large, 10 to 15 kilometers in diameter. Coming from the south at a speed of 20 kilometers per second, it smashed into the crust of the Yucatán Peninsula in Mexico with titanic force, equivalent to 100,000 gigatons of TNT – more than a billion times the energy of the atomic bomb explosion over Hiroshima.

Huge amounts of dust and particles were ejected into the atmosphere and produced an intense pulse of infrared radiation as they returned to Earth’s surface. Temperatures may have risen to 1,500 degrees Celsius in the upper atmosphere, likely killing many animals exposed to the heat. Over 70 percent of the Earth’s forests caught fire, and the huge fires produced huge amounts of soot that darkened the Earth’s surface.

But this was not all. In two new studies, scientists have shown other effects of the collision – a giant global tsunami and an earthquake almost beyond comprehension.

Huge waves

The tsunami was caused when the asteroid hit the ocean next to the Yucatán. Two and a half minutes after impact, a curtain of crumbled rock mass pushed a huge wall of water in front of it that was initially 4.5 kilometers high. Ten minutes after the impact, the wave had subsided somewhat but was still 1.5 kilometers high. It had then traveled 220 kilometers from the impact site and swept across the sea in all directions.

The study, carried out by an international research team and published in the scientific journal AGU Advances, is based on a combination of computer simulations and analyzes of sediments from over 100 geological sites around the world.

An hour after the collision, the tsunami had spread into the North Atlantic, and four hours later the waves were sweeping across the Pacific Ocean. They could travel unimpeded westward from Yucatán because Central America was then under the surface of the ocean.

A day after the impact, the tsunami had crossed the Pacific Ocean and reached the Indian Ocean, and after another day it had reached most of the Earth’s coastlines.

Hard hit dinosaurs

The height of the waves decreased over time but they were still over ten meters high out in the open sea when they entered the North Atlantic and Pacific Oceans. When they then struck over land, they rose dramatically. The worst hit was southern North America, which was closest to Yucatán. Large parts of what was the habitat of North American dinosaurs such as Tyrannosaurus and Triceratops were destroyed.

Calculations suggest that the force of the tsunami, the energy, was 30,000 times greater than the energy of the tsunami that swept across the Indian Ocean and killed 230,000 people in December 2004.

The second study, conducted by scientists from the United States and Colombia, provides evidence that the asteroid also triggered an earthquake, or a series of earthquakes, that were so powerful that the entire planet shook for many months after the impact.

The evidence comes from analyzes of sediment from the moment of impact itself. The sediments are found in several places in the southern United States, in Mexico and on the island of Gorgonilla off the coast of Colombia.

Violent tremors

Faults and deformations in the bedrock show that the entire area was exposed to violent shaking for a long time. The energy released by the quake is estimated at 100 trillion (100,000,000,000,000,000,000,000) joules, which is about 50,000 times more energy than was released by the earthquake that triggered the December 2004 tsunami.

Maybe it’s not so strange that the dinosaurs died out. They, like so many other animals that lived at that time, undeniably had everything against them. And when the radiation, the fires, the tsunami and the earthquake were over, the real death blow came. After the collision, so much dust accumulated in the atmosphere that the sun’s rays were blocked for several months. Temperatures dropped by around 10 degrees Celsius across the planet and plant photosynthesis temporarily ceased. All land animals larger than a cat disappeared. It would take ten million years for the ecosystems to recover – but the Earth has never regained anything like the amazing diversity of the dinosaurs. A worse disaster is hard to imagine.

Facts

Mass extinctions

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