Lunar glass and terrestrial extinctions

Abstract

At the end of the Cretaceous Period, 65 million years ago, the dinosaurs and many other forms of life disappeared suddenly. The agency which destroyed them has recently shown to be the same as the agency which, at intervals of millions or tens of millions of years, scatters glass pebbles and dust (called tektites and microtektites) over huge areas of the earth's surface. After almost a century of study and discusion, it has become clear that the agency involved is either the impact of giant meteorites (asteroids or comets) on the earth's surface, or the eruption of lunar volcanoes. One of the best approaches to this question is through the kinetics of glassmaking. Is it possible that ordinary soil or rock could be converted to a high-silica glass, sometimes of good quality (homogeneous and free of bubbles), during a meteorite impact (in which the heating period is a few tens of seconds at most?). Calculations of the rate of bubble movement and the rates of homogenization make it appear hopeless. A recent study by E. Luft furnishes data confirming these conclusions. The alternative is lunar volcanism. A cloud of ash and pebbles from a lunar volcano, if directed toward the earth, would organize itself into rings like those of Saturn, shadowing the winter hemisphere and so destroying some forms of life. R. Sheldon may have geological confirmation of these ideas.