Gallery Events

Feb

26

2017

Emeritus Prof. John Wasson

Formation of tektites in thermal plumes: no craters required

Location: Slichter 3853
Time: 2:30PM

Tektites are glassy samples with interesting shapes (e.g., teardrops) and compositions similar to soils and shales that formed as a result of weathering the continental crust. Since 1960 the consensus view has been that tektites are crater ejecta. However, high concentrations of 10Be (half-life of 1.5 My) show that tektites are made from soils from the upper 50 centimeters of the crust. The best model seems to be thermal plumes resulting from accreting asteroids or comets that disintegrated and deposited their entire energy in the atmosphere, similar to the 1908 Tunguska event. Figure: Thermal plume after Glasstone and Nolan