Shield volcano

Shield volcanoes tend to form at divergent boundaries, where plates move apart, and at hotspots such as Hawaii. Magma rises through openings in the crust. The magma is typically basaltic, with low viscosity and relatively low gas content.

The lava erupted here is commonly basaltic: it has low viscosity, meaning that it flows easily. It can spread a long distance before cooling, so repeated flows can build broad volcanoes with gentle slopes. These are shield volcanoes.