system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Which evidence made us believe that dinosaurs were extinguished by a meteor?
gpt
Couple of things...

1) There's a significant layer of iridium in the rock layers between the two time periods between dinosaurs and non-dinosaurs.  Iridium is not common on earth but is common in meteors.

2)  There's a huge meteor crater off the Yucatan Penninsula that dates to the same time as the layer of iridium.