Why do shield volcanoes and composite volcanoes have different shapes?
Volcanoes have many different shapes, which are created by various styles of eruption. Geologists classify volcanoes by their shape, eruption style, and mineral composition. Their shapes and eruption styles are determined by many factors, including the pressure and amount of gas and magma (molten rock) rising to the surface, and how much water is seeping down from above and mixing with the magma and gas. Composite volcanoes are a result of alternating eruptions of pyroclastic material and lava flows. The lava flows protect underlying ash deposits from erosion. Due to their relatively high viscosity, the flows cannot flow great distances from their source. Consequently, composite volcanoes are typically high and have very steep slopes. Due to high magma viscosity, composite volcanoes are characterized by highly explosive eruptions, producing a greater volume of pyroclastic material than lava flows. Shield volcanoes are flatter and broader, created by thousands of runny lava flows that p
