Structure of the Earth easily than does the upper mantle (chemical changes within the mantle may also be important). The viscosity of the mantle ranges between 10 and 10 Pa·s, depending on depth. In comparison, the viscosity of water is approximately 10 Pa·s and that of pitch is 10 Pa·s. The source of heat that drives plate tectonics is the primordial heat left over from the planet’s formation as well as the radioactive decay of uranium, thorium, and potassium in Earth’s crust and mantle. The average density of Earth is . Because the average density of surface material is only around , we must
What We Do Is Secret (film) Story". Additional songs used in the film that do not appear on the soundtrack album include: What We Do Is Secret (film) What We Do Is Secret is a 2007 American biographical film about Darby Crash, singer of the late-1970s Los Angeles punk rock band the Germs. Rodger Grossman directed the film and wrote the screenplay, based on a story he had written with Michelle Baer Ghaffari, a friend of Crash's and co-producer of the film. Shane West stars as Crash, while Rick Gonzalez, Bijou Phillips, and Noah Segan respectively portray Germs members Pat Smear, Lorna Doom, and Don Bolles.