Final answer:
Thinner, easy-flowing lavas are rich in silica and aluminum, with dominant minerals such as quartz, muscovite, potassium feldspar, and Na-rich plagioclase, characteristic of felsic igneous rocks like rhyolite and granite.
Step-by-step explanation:
Thinner, easy-flowing lavas are typically rich in silica and aluminum, and they contain minerals such as quartz, potassium feldspar, and Na-rich plagioclase. These types of lavas are associated with felsic or silicic igneous rocks, like rhyolite and granite. The mineralogy of these rocks results in lower density and lower viscosity lavas when they erupt, leading to the flowy nature of these lavas.
On the geological spectrum, these lighter-colored minerals rich in potassium, aluminum, and silica contrast with the darker minerals found in mafic and ultramafic rocks, which contain higher amounts of iron and magnesium. The mafic rocks include basalt and gabbro, which are characterized by a higher density and viscosity. Understanding the mineral content helps geologists identify the types of igneous rocks and their properties.