Rock, in geology, naturally occurring and coherent aggregate of one or more minerals Such aggregates constitute the basic unit of which the solid earth is composed and typically form recognizable and mappable volumes The three major classes of rock are igneous, sedimentary, and metamorphic rock. Rock history can thus be organized around both the sound of cities (philadelphia and detroit, new york city and san francisco, liverpool and manchester) and the spread of youth cults (rock and roll, heavy metal, punk, and grunge). Rock hudson, american actor noted for his good looks and movie roles during the 1950s and ’60s, including magnificent obsession, giant, and pillow talk, and for the tv series macmillan and wife in the 1970s Rock music is a form of popular music that emerged in the 1950s and can be defined as “a form of music with a strong beat”—it is difficult to be much more precise
It is also called rock and roll. In britain, as in the rest of europe, rock and roll had an immediate youth appeal—each country soon had its own elvis presley—but it made little impact on national music media, as broadcasting was still largely under state control. The music industry was rescued from its economic crisis by the development in the 1980s of a new technology, digital recording Vinyl records were replaced by the compact disc (cd), a technological revolution that immediately had a conservative effect. Rock remains the most democratic of mass media—the only one in which voices from the margins of society can still be heard out loud Yet, at the beginning of the 21st century, rock and the music industry faced a new crisis.
