Pacific Ocean closed loop of the andesite line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the Pacific basin. Here basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the andesite line, volcanism is of the explosive type, and the Pacific Ring of Fire is the world's foremost belt of explosive volcanism. The Ring of Fire is named after the several hundred active volcanoes that sit above the various subduction zones. The Pacific Ocean is the only ocean which is almost
Circum-Superior Belt features are present in the Circum-Superior Belt, including dikes, sills and volcanics that comprise geologic formations. This geologic belt is considered to be a large igneous province because its magmatic rocks were emplaced over an extremely short geological time span. Even though the Circum-Superior Belt was emplaced during an extremely short geological time span, the associated magmas were probably derived from a number of separate sources. Most of the Circum-Superior Belt lies along the margin of the Superior Craton, which is the most extensive fragment of Archean crust on Earth. However, a number of igneous rocks within the Superior craton