Theories to why dinosaurs disappeared:
Some scientists think dinosaurs died out due to rapid evolution of flowering plants.
It goes like this: Up until the flowering plants came, the dinosaurs ate things like pine needles from evergreen trees. Then flowering plants came, replacing many of the pine trees. Dinosaurs didn't have time to switch their diet to flowers and, as a result, died of starvation.
Another recent and popular theory is: A giant meteorite, 6 miles across, struck the Earth. This collision would have produced an explosive force and damage similar to that of nuclear war. Vast amounts of dust, debris, and ash would have spread quickly around the planet, blocking out the sunlight reaching Earth's surface. Lack of sunlight is believed to have lasted for several months and to have caused temperatures to drop worldwide from 66 degrees Fahrenheit to about 14 degrees. Without sunlight to perform photosynthesis, many plants would have died, causing a domino-like effect on the food chain, including the dinosaurs.
Another theory involves a series of volcanic eruptions in what is now India that formed what we call the Deccan Traps. This massive volcanic episode would likely have had massive climatic changes worldwide. It has even been proposed that the shockwaves from the asteroid impact may have triggered the vulcanism.
