GEOLOGY

Detailed explanation-1: -If it has high viscosity (like a milk shake) and no dissolved gases, the lava oozes slowly out to form a bulbous dome which hardly moves at all (see low water/high silica figure).

Detailed explanation-2: -Rhyolitic magmas tend to have even higher viscosity, ranging between 1 million and 100 million times more viscous than water.

Detailed explanation-3: -High viscosity lavas flow slowly and typically cover small areas. In contrast, low viscosity magmas flow more rapidly and form lava flows that cover thousands of square kilometers.

Detailed explanation-4: -So, mafic lavas are hot, low in silica and volatiles, and have relatively low viscosity. They flow easily outward from the vent (where it comes out of the ground), and may travel great distances before completely solidifying. Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity.

Detailed explanation-5: -A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10, 000 to 100, 000 times that of water.