Why did most dinosaurs become extinct? Possible explanations abound; the difficulty lies in testing these ideas.

The Age of Dinosaurs ended 65 million years ago with mass global extinctions. Theories on the cause of this episode are controversial. Recent findings of iridium layers worldwide, with associated shocked quartz in some areas, clashed with traditional theories of extinction caused by gradual climatic change.

It is difficult to analyze these extinctions, partly because events that occurred so long ago cannot be dated precisely. The most current dating methods available have an error margin of two million years, plus or minus.

Extinction Theories: Extraterrestrial Causes

impact of an asteroid or comet generated a deadly cloud of dust and steam that killed plants, raised temperatures, and increased the amount of carbon dioxide in the atmosphere; burning particles from the impact may have sparked global wildfires.
a supernova exploded near Earth, bombarding the planet with cosmic rays; increased radiation levels damaged plant and animal chromosomes.

Extinction Theories: Terrestrial Causes

climate changes: as inland seas dried up, overall climates became cooler and drier, and seasonal weather patterns become more extreme
increased volcanic activity: volcanos erupted vast clouds of ash and dust that blocked sunlight and cooled climates globally
changing plant populations: familiar food sources were lost

• iridium layer
• Extinction is a natural, inevitable part of the evolutionary process. Some species die out, new species appear. Extraordinary animals like dinosaurs, however, tend to evoke spectacular guesses as to the reason for their demise. Without a doubt, the subject will continue to spark much research and debate.