Across the entire planet where it has not been eroded or destroyed in land movements there is a thin gray line In Italy it is one centimeter thick in America it stretches to its maximum of three centimeters but it is all the same thin gray line laid into the rock some 65 million years ago and it bears witness to a cataclysmic event experienced only once in the history of Earth It is called the CretaceousTertiary KT Boundary and geologists believe it is the clue to the death of the dinosaurs and the ultimate reason why mammals and humans inherited the Earth This radio broadcast explores what happened 65 million years ago how this extraordinary line was created across the Earth the discovery of the KT Boundary and whether the KT Boundary really holds the key to the death of the dinosaurs The broadcast discusses the greenhouse climate and mass extinction of 65 million years ago how the Yucatan crater and the spike in iridium in the KT layer provide geological evidence of an impact the relation of the Deccan Traps of India to the disappearance of the dinosaurs how mammals that were held back ecologically were able to take over after the KT Boundary event why freshwater vertebrates that can burrow at the bottom of lakes were able to survive major extinctions and how plants do not seem to have been as affected as animals by the major extinction events of the past The broadcast is 42 minutes in length