Structure of the Earth obducted onto the continental crust and preserved as ophiolite sequences. Many rocks now making up Earth's crust formed less than 100 million (1) years ago; however, the oldest known mineral grains are about 4.4 billion (4.4) years old, indicating that Earth has had a solid crust for at least 4.4 billion years. Earth's mantle extends to a depth of 2,890 km, making it the thickest layer of Earth. The mantle is divided into upper and lower mantle. The upper and lower mantle are separated by the transition zone. The lowest part of the mantle next to the core-mantle boundary is
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.