How and when did the dinosaurs go extinct?
The dinosaurs (except the birds) went extinct 65 million years ago, probably due to the after-effects of an asteroid impact off the Yucatan Peninsula. There are a lot of theories about why this K-T (Cretaceous-Tertiary) extinction occurred, but a widely accepted theory (proposed in 1980 by physicist Luis Alvarez and his son Walter Alvarez, a geologist), is that an asteroid 4-9 miles (6-15 km) in diameter hit the Earth about 65 million years ago. The impact would have penetrated the Earth’s crust, scattering dust and debris into the atmosphere, and caused huge fires, volcanic activity , tsunamis, severe storms with high windsand highly acidic rain . The impact could have caused chemical changes in the Earth’s atmosphere, increasing concentrations of sulfuric acid, nitric acid, and fluoride compounds. The heat from the impact’s blast wave would have incinerated all the life forms in its path. The dust and debris thrust into the atmosphere would have blocked most of the sunlight for month
