Many thousand years of dormancy are expected between large explosive eruptions of volcanoes in the Garibaldi Belt. A possible explanation for the lower rates of volcanism in the Garibaldi chain is that the associated terrain is being compressed in contrast to the more southern portions of the Cascade Arc. In continental rift zones, magma is able to push its way up through the Earth's crust rapidly along faults, providing less chance for differentiation. This is likely the case south of Mount Hood to the California border and east-southeast of the massive Newberry shield volcano adjacent to the Cascade Range in central Oregon because the Brothers Fault Zone lies in this region. This rift zone might explain the massive amounts of basaltic lava in this part of the central Cascade Arc. A low convergence rate in a compressional setting with massive stationary bodies of magma under the surface could explain the low volume and differentiated magmas throughout the Garibaldi Volcanic Belt. In 1958, Canadian volcanologist Bill Mathews proposed there could be a connection between regional glaciation of the North American continent during glacial periods and higher rates of volcanic activity during regional glacial unload of the continent. However, this is hard to predict due to the infrequent geological record in this region. But there is specific data, including the temporal grouping of eruptions synglacially or just postglacial within the Garibaldi Belt, that suggests this could be probable.