KT boundary KT Boundary: In the BBC radio program, Melvyn Bragg and the other panelists discuss the geological KT boundary that led to the extinctionof dinosaurs and the rise of mammals on earth. The thin grey line of clay inside the earth seen across the entire planet is known as K T Boundary. ‘K’ stands for cretaceous period and ‘T’ for tertiary period. Particular land movements in some areas have made this line to disappear in some areas. This layer is of three inches’ thickness in Central America and in Italy it has only a thickness of one centimeter. This unique layer in terms of its contents and age is believed to have been created sixty five million years ago. Geologists believe this demarcating line to be a clue to the extinction of dinosaurs and the spread of mammals on the earth. The contents of this layer are mainly clay in the bottom and in the upper layer it has got mixtures of minerals like quarts and broken pieces of prismatic crystal substances. The presence of iridium in this layer is very high. Supporting the theory of the mass impact as the presence of it is very less in earth whereas it is abundant in asteroids.
The thickness of KT Boundary: Panelists unanimously agree that there is variation in the thickness of the layer. It becomes thinner in Northern America and Canada. But in Italy it is just one centimeter in thickness. The panelists observe that the line gets thinner when it moves from Southern American states into the Northern American states to Canada. The thickness of the layer is three centimeters in America whereas it is only 1 cm thick in Italy owing to the climate impacts on the boundary.
KT Boundary and the Extinction of Dinosaurs: The most scientists believe that dinosaurs became extinct because of a single catastrophic event. a massive asteroid impact and gradually the earth witnessed the spread of mammals. The fall of the asteroid led to a kind of situation on the atmosphere where there was no sunlight and thus there was no process of photosynthesis which made a greater crack in the food chain which led to massive extinction. As a result, comparatively bigger animals got extinct whereas mammals and other minor organisms could survive as they were able to hibernate .Scientists are of the opinion that dinosaurs wanted a large area to live in and they could not withstand the impact of asteroid fall and the aftereffects.. In the talk, panelists tell us of crocodiles and turtles who could live underneath the water after the mass impact.
Alternate Theory: Melvyn Brag after probing through many questions on the cataclysmic event that led to the extinction of dinosaurs and the rise of the mammals asks to Simon Kelley whether there is any other theory to substantiate the extinction of dinosaurs other than the massive impact. The answer is ‘no’. The alternate theory of great volcanic eruption and flow of lava that led to massive extinction is not much supported in the discussion. Jane Francis also observes that the alternate theory does not support the uniqueness of time and age of the K T boundary across the planet.
BBC iPlayer Console-In Our Time: The KT Boundary. Web. 13 June 2010.