A volcano that has not erupts, and lava flows down a mountainside. Which statement best describes this eruption?

This is a quiet eruption caused by low-viscosity magma.

Explanation:

The viscosity of magma is determined by the amount of silica content in it. The higher the silica content the higher the viscosity. Viscous lava usually erupts with an explosion due to the held up gases within by the viscous fluid rock. As the pressure releases, the gases expand violently and the eruption occurs.  In low viscous magma the gases escape easily through the light magma hence the eruption is not violent.

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