Dinosaur Extinction Theories

Asteroid Impact Theory

65 million years ago a huge asteroid named "Chicxulub" hit the Mexico, sending large amounts of ash into the atmosphere. This ash blocked out the sun for thousands of years, decreasing global temps, reducing photosynthesis and killing many forms of plant life. Also, producing acid rain which killed many forms of plant and animal life. Without plant, herbivores died, soon after carnivores including dinosaurs would have died, too.

Volcanism Theory

65 million years ago many volcanoes around the world flooded earth's atmosphere with CO2 trapping heat from the sun and causing global warming. It is believed that the warming of earth caused reptiles to produce unhealthy sperm and eggs, resulting in the extinction of dinosaurs.

Size

Maybe their size was their demise. Dinos are the largest terrestrial animals ever known. They require a lot of food for survival. Possibly their food sources were just used up and couldn't replenish themselves fast enough.

Disease

Other biologists have suggested that a disease could have spread through the dino species.

Climate

Some biologists believe that the dinosaurs just could not adapt to the changing climate that happens naturally over time. Possibly the dinos couldn't adapt to the cold and died out. This could explain why some species of reptiles still exist. The ones that could migrate or adapt survived.