Basaltic magma has the lowest viscosity, so more of it reaches the surface; the more viscous rhyolitic magmas are so sluggish that they tend to be trapped deep below the surface where they cool, solidify, and grow into the larger mineral crystals of plutonic rocks.Group startsTrue or False

Beneath continents, rising basaltic magmas are contaminated by sediments and continental-crust rocks, altering magma compositions; the resultant andesitic-to-rhyolitic magmas have high contents of SiO2SiO2 , relatively low temperatures, and high viscosity.Group startsTrue or False

Decreasing the pressure on hot rock generates most magma. Group startsTrue or False

The lowest temperatures and highest SiO2SiO2 contents occur in rhyolitic magma, material so viscous that it commonly does not flow.Group startsTrue or False

About 80 percent of the magma reaching Earth's surface is basaltic, with only about 10 percent andesitic and 10 percent rhyolitic.Group startsTrue or False

What is the difference between magma and lava?