sialThe uppermost of the two main rock-classes in the Earth's crust. Sial rocks are so-called because their main constituents are silicon and aluminum. They make up the material of the continents and overlay the sima. The sial is less dense than the sima nd is generally not carried beneath the surface when subduction. Related category GEOLOGY AND PLANETARY SCIENCEAlso on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |