- an assemblage of rocks, rich in silica and magnesium, that constitutes the lower layer of the earth's crust and is found beneath the ocean floors and the sial of continents.
Origin of sima1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- the silicon-rich and magnesium-rich rocks of the earth's oceanic crust, the most abundant individual rock being basalt
- the earth's continental lower crust, probably comprised of gabbro rather than basalt
C20: from si (lica) + ma (gnesia)