Why did the dinosaurs die out?

Until recently there were a number of theories about the extinction of the dinosaurs, but now recent reports are making the most likely cause of the dinosaur extinction a huge asteroid which hit the Earth with the force of 10,000 hydrogen bombs. It is thought that the asteroid hit part of southern Mexico called the Yucatan peninsula and caused a crater about 125 miles across. The asteroid was probably about 6 miles across and travelling at about 20,000 mph when it crashed and it is thought that it would have caused an earthquake about 1000 times stronger than the worst quakes today. This crash would have thrown a lot of dust into the air causing the sun to be blocked out and making the Earth much colder for a long time. This would have made plants grow less well and therefore made food less abundant. Since dinosaurs were so big they needed an almost constant food supply. So this lack of food would have killed off the larger animals first. But itÕs important to remember that dinosaurs were in decline for about 8 million years before the mass extinction anyway, probably because of a slow climate change; when the asteroid impacted it was just the final straw.