Question

What are the different shapes of a volcano and how are their shapes determined?

Answer 1

Volcanoes form when molten rock, created inside the crust or upper mantle of the Earth, moves upward and erupts on the Earth’s surface. Molten rock is less dense than the surrounding rock, so it is buoyant and rises, just like hot air. Each eruption can produce layers of lava that will later become volcanic rock. These layers build the volcano. Depending on how viscous the lava is will depend on the shape. The word "viscous" is explained in the storybook called "Lucy Lava."

Volcanoes have several shapes, which are controlled by the composition of the magma and the nature of its eruption. If a volcano produces very fluid lava (low in the compound SiO2, or silica), the magma flows a long distance before it cools, making a flat, shield-shaped volcano. If the volcano produces very sticky magma (high in silica) it tends to have an explosive eruptive style that includes lava, pyroclastic flows, and ash. This material piles up right around the volcano, forming a steep cone, a classic volcano shape. Volcanoes that are a built from ash and cinders usually have steep sides, but tend to erode quicker than volcanoes built from lava.