Lava

Main article: lava
Lava flows from stratovolcanoes are generally not a significant threat to people because the highly viscous lava moves slowly enough for people to move out of the path of flow. The lava flows are more of a property threat.
However, not all stratovolcanoes have viscous lava. Mount Nyiragongo is dangerous because its magma has an unusually low silica content, making it quite fluid (even when comparing to Hawaiian lava) and having lower viscosity. Compounded by the very steep slope of Nyiragongo gives the lava the ability to flow at up to about 100 km/h (60 mph).