What is the defining feature of a shield volcano?

A shield volcano is characterized by its gently sloping sides and the type of lava it produces. The defining feature of shield volcanoes is their formation from low-viscosity, basaltic lava flows that can travel long distances. This fluid lava allows the volcano to spread out over a wide area, creating the characteristic broad and gently sloping profile.

Unlike stratovolcanoes, which have steep sides due to thicker, more viscous lava that does not travel far, shield volcanoes promote the smooth, gradual buildup of their shapes. The fluid nature of basaltic lava contributes to the gentle slopes, as each eruption can produce extensive layers of thin, flowing lava rather than explosive eruptions that create significant ash deposits or steep-sided structures.