What is a shield volcano?

A shield volcano is characterized by its broad, dome-shaped structure that results from the eruption of low-viscosity lava. This type of lava can flow easily over great distances, allowing it to spread out thinly, which contributes to the gentle slopes of the volcano. The eruptions of shield volcanoes are typically non-explosive because the low viscosity of the lava allows gas to escape easily, preventing the buildup of pressure that leads to explosive events. The classic example of a shield volcano is Mauna Loa in Hawaii, which showcases the vast and gentle slopes formed by repeated lava flows.

Other options suggest different types of volcanic structures or features: steep, conical volcanoes are typically stratovolcanoes formed by more viscous lava leading to explosive eruptions; volcanic structures made primarily of ash and cinders are cinder cone volcanoes, which are steep and small; and underwater volcanoes, often referred to as seamounts or mid-ocean ridges, are different from shield volcanoes entirely in their formation and characteristics. Understanding these distinctions helps clarify why shield volcanoes hold their unique form and eruption style.