What Is Basaltic Lava? When you envision lava in your mind, you likely think about rivers of molten rock flowing over a landscape much like Hawaii. This idealized vision of lava is actually basaltic lava. Basaltic lava is the most abundant lava on earth and is the lava most commonly depicted in pictures and media.
Pillow flows are produced by the piling up of individual pillow lava lobes. As a pillow flow forms, the newest pillows are erupted from the top of the stack and flow outward a limited distance before freezing, a process which tends to produce steep-sided mounds or ridges which can grow to be 10's of meters thick.
Rhyolite can be considered as the extrusive equivalent to the plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Due to their high content of silica and low iron and magnesium contents, rhyolite melts are highly polymerized and form highly viscous lavas.