Mount Garibaldi is the largest volcano in southernmost British Columbia. Like other stratovolcanoes, it is composed of many layers of hardened lava, tephra, and volcanic ash. Eruptions are explosive in nature, and the most common form is the Peléan style, which involves viscous magma, glowing avalanches of hot volcanic ash and pyroclastic flows. The source magma of this rock is classified as acidic, having high to intermediate levels of silica (as in rhyolite, dacite, or andesite). The tephra deposits have lower volume and range than the corresponding Plinian and Vulcanian eruptions.