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

Less than 20 percent of Earth's magma extruded through volcanism occurs at oceanic spreading centers. 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

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

At a depth of 32 km, basaltic rock melts at around 1,400°C but this same rock will melt at only 1,250°C at Earth's surface.  Group startsTrue or False

Rhyolitic magmas are:Selected answer will be automatically saved. For keyboard navigation, press up/down arrow keys to select an answer.amafic in compositionbcharacterize the magma that erupts at mid-ocean ridgeschigh in silica contentdform at around 800°CeC and D