The basalt is a effusiva cliff of vulcanica origin, of dark or black color with a content of silica (SiO2) (relatively low smaller of 50% usually). The basalt is formed mainly from plagioclasio calcic and pyroxenes, some basalts can be also rich in olivina. The intrusivo correspondent of the basalt is the gabbro. The basalt can be introduced with aspect that goes from porfirico to microcrystalline to vetroso. It comes fastly from a made solid magma to contact dell' air or dell' water and is the main cliff constituted the advanced part of the oceanic crust. The basaltic magmas are formed for fusion from decompression of the terrestrial cape.