Sial

In geology, sial is an antiquated[1] blended term for the composition of the upper layer of Earth's crust, namely rocks rich in aluminium silicate minerals.

Geologists often refer to the rocks in this layer as felsic, because they contain high levels of feldspar, an aluminium silicate mineral series.

The sial is often contrasted to the 'sima' (another antiquated blended term),[5] the next lower layer in Earth, which is rich in silica and magnesium and is often exposed in the ocean basins; and the nickel-iron alloy core, sometimes referred to as the 'Nife'.

These geochemical divisions of Earth's interior (with these names) were first proposed by Eduard Suess in the 19th century.

This model of the outer layers of Earth has been confirmed by petrographic, gravimetric, and seismic evidence.