Sialic refers to rocks and magmas composed mostly of silica and alumina, typically forming the upper layer of the Earth's continental crust. These rocks, such as granite and rhyolite, are lighter in color and have a lower density than deeper crustal materials. Geologists use the term to distinguish the buoyant continental crust from the denser oceanic crust beneath it.
Heard on the job
The drill core shows we have hit a sialic intrusion, mostly granite and quartz, right above the contact zone.
Insider tip
The term is a portmanteau of silicon (Si) and aluminum (Al), historically used to describe the continental crust.
Do not mix it up with
- Simatic: Sialic rocks are rich in silica and alumina, whereas simatic rocks are rich in silica and magnesia.