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A large asteroid struck the sea just north of the Yucatán Peninsula in Mexico, about 66 million years ago causing catastrophic changes to the climate. It also caused destruction on a global scale and the mass extinction about 75% of all plant and animal species on Earth, including non-avian dinosaurs, marine reptiles, and many marine invertebrates. This marked a significant turning point in Earth's history, leading to the dominance of mammals.
The asteroid, about ten km (six miles) in diameter, left a crater about 180 km (110 miles) in diameter and 20 km (12 miles) in depth. It is the second largest known impact crater on Earth.
The estimated velocity of the asteroid's was 20 km/s (12 miles/second) and the kinetic energy of the impact was equivalent to 72 teratonnes of TNT (a number with 12 zeros). For comparison, the explosive power the Hiroshima atomic bomb, was only 15 kilotonnes of TNT (a number with only three zeros).
(The equivalent of 72 teratonnes of TNT is 300 ZJ (or 300 zettajoules, a unit of energy with 21 zeros. In 2019, total world energy consumption was about 630 ZJ).
The impact triggered a seismic event with an estimated magnitude of between 9 and 11 Mw (corresponding to an extremely powerful earthquake), while winds exceeded 1,000 km/h (620 mph) near the impact site. The movement of water filling the crater and related seismic activity generated mega-tsunamis over 100 metres (330 ft) tall that reached to what are now Texas and Florida.
The impact blasted up to 25 trillion metric tons of excavated material, in a cloud of hot dust, ash and steam, into the atmosphere. Some of this material was fast enough to escape the Earth's gravity while most of it fell back to Earth, heated to incandescence on re-entry. This heated Earth's shallow seas and, on land, ignited wildfires that may have devastated about 70% of the planet's forests. Fossil evidence of an instantaneous extinction of animals was found in New Jersey, 2,500 km (1,600 mi) away from the impact site.
Because of the relatively shallow water, the impact vaporized sulfur-rich gypsum which was injected into the atmosphere with super heated steam. This global dispersal of sulfates had a catastrophic effect on the climate worldwide, causing a global winter and generating acid rain that devastated all life. For more than a decade, sunlight was blocked from reaching the surface of Earth by the dust particles in the atmosphere, cooling the surface dramatically. Photosynthesis by plants was interrupted, affecting the entire food chain. The dust covered the entire surface of Earth for many years, creating a harsh environment for living things. The destruction of carbonate rocks increased the amount of atmospheric carbon dioxide causing a sudden greenhouse effect.
A series of massive volcanic eruptions in what is now the Deccan Plateau of western India may also have contributed to the extinctions; as these released enormous amounts of lava and gases for many years.
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