Chicxulub Crater
The Chicxulub Crater is often considered to be the smoking gun of the asteroid impact theory. Its sheer size indicates that the asteroid whose collision ultimately brought about the extinction delivered an amount of energy several times greater than that which results from the explosion of an atomic bomb. A collision from an asteroid whose impact caused the formation of the Chicxulub likely would have caused tsunamis and earthquakes, and it is quite possible that a cloud of dust, forming as a direct result of the collision, would have obscured the sun, drastically lowering temperatures and leading to a mass extinction.