We will begin with the most popular extinction event first:
The Cretaceous- Paleogene (K-Pg) Boundary
How did we find out about this asteroid, the crater, and the dinosaur extinction in the first place?
It was a complete accident!

The K-Pg Extinction Event Articles:
*Read about the The Alvarez Hypothesis in the dropdown menu “An Asteroid Killed the Dinosaurs?”
*Researchers Find Proof of Dinosaur’s Asteroid Demise introduces the researchers and dimensions of the Chicxulub Crater.
* Minutes to Weeks After the Impact– core samples and research completed from the 2016 expedition revealed what happened at impact to days, weeks, and perhaps, years later. The professional paper called “The First Day of the Cenozoic” was written by the scientists of Gulick, et al., 2019 is the basis of this article.
*Results of the Impact Devastation– explains post-impact effect worldwide and brings an end to the asteroid hypothesis -thanks to the work of Dr. Gulick and the scientists of the IODP- Expedition 364.

The Lunar and Planetary Institute also has wonderful information on this asteroid event.
https://www.lpi.usra.edu/science/kring/Chicxulub/discovery/