How do the scientist know K-T extinction took place?

Answer 1

1. There is an unusually high concentration of Iridium found at the K-T boundary. Iridium loves to stick to Iron, so the Iridium that would have been on Earth originally is in the Iron core, not in the crust. Therefore, the Iridium must have been introduced by an external source; a meteorite.

2. Shocked Quartz is found at the K-T Boundary all around North America. Shocked Quartz is only produced naturally by bolide impact. Since the K-T meteorite impacted in the Mexican peninsula, it makes sense that the shocked quartz would be found only in relatively close proximity to the impact site.

3. Microtektites, which are normally found at meteorite impact sites, are found at all K-T boundary impact sites.

4. There is a massive impact crater in the Mexican peninsula.

5. In many of the K-T Boundary sections there is a fine layer of ash (disseminated Carbon) from the global wildfires that were caused.

6. There was a fern spike because other flowering plants stopped producing pollen for awhile.

7. Microdiamonds have been detected at K-T Boundary sites, but not above or below.

Answer 2

Since there are no more known dinosaurs living on this planet, dinosaurs are considered to be extinct. If a dinosaur is found to actually be living in some exotic part of the world, then that species will be removed from the extinct list.

This can also apply to modern animals, like the coelacanth, which was thought to be extinct, but then found again by fishermen in Africa in 1938.

Answer 3

They guess, no-one knows. There's theories about meteors and ice ages, but its a mystery really.