Final answer:
The mass extinction of dinosaurs occurred 65 million years ago at the end of the Cretaceous period, caused by a meteorite impact off the coast of the Yucatán Peninsula, with iridium levels and geological evidence supporting the asteroid impact hypothesis.
Step-by-step explanation:
The huge meteorite that caused the mass extinction of the dinosaurs and many other species struck the Earth during the Cretaceous period, about 65 million years ago. This catastrophic event led to a mass extinction, marking the end of the age of dinosaurs and paving the way for the age of mammals. Geological evidence for this event includes a worldwide layer of sediment rich in iridium and other elements that are rare on Earth but abundant in asteroids and comets. This layer, identified first in 1979, is also characterized by minerals indicative of the high temperatures and pressures of a massive impact, further supporting the asteroid impact hypothesis.