The impact of a large asteroid or comet with the Earth 66 million years ago, which is believed to have led to the extinction of the dinosaurs, is thought to have caused a massive seismic event known as a "mega-earthquake." This event would have been caused by the massive amount of energy released by the impact, which would have caused the Earth's crust to crack and shift.

The exact duration of the mega-earthquake is not well understood, but it is thought to have lasted for weeks to months, based on studies of the size and structure of the Chicxulub crater, the massive impact crater formed by the asteroid or comet. This seismic activity would have caused the widespread ground rupture, landslides, and tsunamis, leading to widespread devastation and contributing to the mass extinction of life on Earth.