Science Olympiad Dynamic Planet Practice Test

What feature of stratovolcanoes allows for greater pressure build-up compared to shield volcanoes?

1. Multiple structures from different eruptions

2. Thinner lava flow

3. Shallower slopes

4. Lower elevation

The correct answer is: Multiple structures from different eruptions

Stratovolcanoes are characterized by their steep, conical shapes and are built from alternating layers of lava flow, ash, and other volcanic materials. This layered structure allows stratovolcanoes to have a more complex internal plumbing system than shield volcanoes, which typically have a more uniform and broad structure built from relatively fluid basaltic lava that spreads over larger areas. The feature of having multiple structures from different eruptions contributes to a larger build-up of volcanic materials that can create a denser and more viscous magma. This can lead to higher pressure accumulation in the magma chamber beneath the volcano due to the viscous nature of the magma trapped within these layers. As pressure builds up over time, it can result in more explosive eruptions when the conditions eventually allow for the release of that pressure. In contrast, shield volcanoes generally produce fluid lava that flows easily and allows gases to escape more readily, which typically prevents significant pressure build-up compared to the more viscous magma found in stratovolcanoes. This fundamental difference in magma characteristics and eruption styles is why stratovolcanoes can experience greater pressure accumulation leading to explosive eruptions.