- Tunguska, Siberia (1908) -- impact of a 30-60 meter stony meteorite, exploding before contact (no crater). Released 10-15 megatons of energy (ie an H-bomb).
A picture of the impact site
- The K/T Event (or, The Dinosaur Killer)
The most recent mass extinction came between the Earth's Cretaceous and Tertiary Periods, about 65 million years ago. This included the dinosaurs. What happened to cause this mass extinction? Best current theory: impact!Luis Alvarez (1980) studied clay layers dating from the K/T boundary, and found anomolously high levels of iridium. Iridium is not common on Earth, but is found in meteorites. Iridium was also found throughout the earth, in layers which date to the K/T boundary.
Current thinking has a 10-km meteoroid impacting the Earth 65 million years ago, causing the climate changes that resulted in the mass extinction. A possible site (Chicxulub) has been identified, in the Yucatan, buried under sedimentary rock.