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 has been suggested for magmatism of the 2,215 million-year-old Nipissing sills as well, which the Ungava dike swarm could have transported magma to the Nipissing sills area. Before 2003, all magmatism of the Circum-Superior Belt was thought to only occur along the outer margin of the Superior craton. However, the Pickle Crow dike was discovered in 2003 in the interior of the Superior craton and it has since been recognized as a magmatic event related to the Circum-Superior Belt. The dike is dated to 1,880 million years old and associated dikes are traced for at least . These dikes likely