In Canada, potentially active volcanoes are found only in British Columbia and the Yukon Territory, where they represent cinder cones, shield volcanoes, and stratovolcanoes. Magma composition controls how a volcano erupts. Low-viscosity magmas (basalt) erupt effusively and represent a low-level hazard. Magmas with higher viscosity (dacite) often erupt explosively, creating significant, far-reaching hazards. The explosion creates small rock fragments or ash that is often carried high above the volcano. These abrasive particles, caught in high-altitude winds, are carried for hundreds of kilometres and affect equipment with moving parts. Hot avalanches of semi-molten rock, or pyroclastic flows, can destroy large areas around the volcano. Additionally, when they descend snow-covered flanks, they can lead to catastrophic melting, sending mud and water cascading into surrounding drainage systems. Even long after an eruption, denuded slopes and unstable rock faces can make the area prone to floods and rock avalanches.