Sixty-five million years ago, more than three-fourths of all plant and animal species living on Earth became extinct. This event is known as the K-T mass extinction because it occurred at the boundary between the Cretaceous (K) and Tertiary (T) time periods. The most famous group of animals to perish was the dinosaurs.

What caused the K-T mass extinction to occur? What events contributed to the demise of the dinosaurs? In this investigation, you will conduct research, analyze evidence, and build a case to support a theory that explains the cause of a mass extinction.