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
Innovation and Its Discontents Innovation and Its Discontents Innovation and Its Discontents: How Our Broken Patent System Is Endangering Innovation and Progress, and What To Do About It is a book () by Adam B. Jaffe and Josh Lerner. Princeton University Press published the book in 2004. The authors of the book outline changes made to the patent system in the United States in the late 1980s and early 1990s which they say has led to a situation in which patents have become extremely powerful economic weapons, and are being issued irresponsibly and at an unreasonable rate. The end result, the authors claim, is