Because the Silverthrone region is in a remote and exceptionally rugged part of the Coast Mountains, danger from lava flows would be low to moderate. Magma with high to intermediate levels of silica (as in andesite, dacite or rhyolite) commonly move slowly and typically cover small areas to form steep-sided mounds called lava domes. Lava domes often grow by the extrusion of many individual flows less than thick over a period of several months or years. Such flows will overlap one another and typically move less than a few meters per hour. But lava eruptions at Silverthrone Caldera can be more intense than those at other Cascade volcanoes. Lava flows with high to intermediate levels of silica rarely extend more than from their source while Silverthrone has produced a long andesitic lava flow in the Pashleth Creek and Machmell River valleys. There is also evidence lava flows may have once partly blocked or at least altered the course of the Machmell River. Renewed activity in this area could disrupt the course of the river and have a serious impact on people living or working downstream.