- published: 10 Jan 2016
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In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.
The Earth's outer solid layer, the lithosphere, is made of rock. Three majors groups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology.
Rocks are generally classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into three types: igneous, sedimentary, and metamorphic. They are further classified according to particle size. The transformation of one rock type to another is described by the geological model called the rock cycle.
Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust (example granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta (examples pumice and basalt).
Sean Justin Penn (born August 17, 1960) is an American actor, screenwriter and film director, also known for his left-wing political and social activism (including humanitarian work). He is a two-time Academy Award winner for his roles in Mystic River (2003) and Milk (2008), as well as the recipient of a Golden Globe Award for the former and a Screen Actors Guild Award for the latter.
Penn began his acting career in television with a brief appearance in a 1974 episode of Little House on the Prairie, directed by his father Leo Penn. Following his film debut in 1981's Taps and a diverse range of film roles in the 1980s, Penn emerged as a prominent leading actor with the 1995 drama film Dead Man Walking, for which he earned his first Academy Award nomination and the Best Actor Award at the Berlin Film Festival. Penn received another two Oscar nominations for Sweet and Lowdown (1999) and I Am Sam (2001), before winning his first Academy Award for Best Actor in 2003 for Mystic River and a second one in 2008 for Milk. He has also won a Best Actor Award of the Cannes Film Festival for She's So Lovely (1997), and two Best Actor Awards at the Venice Film Festival for Hurlyburly (1998) and 21 Grams (2003).