While there have been many theories on what caused the extinction of the dinosaurs--excessive size, the greenhouse effect, egg predation, non-viable eggs, replacement by mammals, disease, etc. But, recently, scientists theorize that a meteor collided with the earth, ejected dust and debris to such thickness that the sunlight was blocked for a long time, so long that the plants died. Without food, the herbivores died. While the carnivores could subsist on the carcasses, once all these carcasses were gone, they, too, starved to death.
In the 1980s the father-son team of Luis and Walter Alvarez discovered a layer of iridium in the K-T Boundary. They theorized that a hug asteroid struck the earth. Not only would there be dust, but forest fires would create smoke as well. The earth would be cooled as the sunlight could not penetrate it and tremendous climatic changes would occur.
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