The GVB extends north from the Watts Point volcano to at least as far as the Meager massif. Because little is known about the volcanoes north of the massif, such as the Silverthrone and Franklin Glacier volcanic complexes, experts disagree about their nature. Some scientists regard the Silverthrone Caldera as the northernmost volcano of the Garibaldi Volcanic Belt, while others contend that the geology of the massif more closely matches that of the GVB. It is also unclear whether the Milbanke Sound Cones are part of the Garibaldi Belt or formed by different tectonic processes. However, there is evidence the Silverthrone and Franklin Glacier complexes are related to activity at the Cascadia subduction zone. Geologically these two volcanoes contain the same rock types as those found elsewhere in the Cascade Arc, including rhyolites, dacites, andesites and basaltic andesites. Such rock types are produced by subduction zone volcanism indicating volcanism at Silverthrone and Franklin Glacier is probably related to subduction. If these two volcanoes are true Cascade Arc volcanoes, the Mount Meager massif is not the northernmost volcano of the Garibaldi Belt or the Cascade Arc.