Composite volcanoes are typically described as being which of the following?

Composite volcanoes are typically described as being which of the following?

• A. Shield-like with quiet lava flows
• B. The most dangerous and erupt explosively
• C. Formed by basaltic lava flows only
• D. Form only underwater

Answer: (B)

Composite volcanoes form from alternating layers of viscous lava and erupted volcanic material, like ash and pumice. That viscosity traps volcanic gases, so pressure builds until a dramatic explosive eruption blasts out ash clouds, pumice, and hot gases, often followed by pyroclastic flows. This combination of a layered structure and highly explosive eruptions makes them the most dangerous type of volcano, which is why that description fits best. They aren’t shield volcanoes, which are broad, gentle sloped constructs built from low-viscosity basalt flows that erupt quietly. They aren’t limited to basaltic lava, since composites typically involve more viscous magmas such as andesite or rhyolite. And they aren’t restricted to underwater settings; many composite volcanoes form on land at subduction zones.

Composite volcanoes form from alternating layers of viscous lava and erupted volcanic material, like ash and pumice. That viscosity traps volcanic gases, so pressure builds until a dramatic explosive eruption blasts out ash clouds, pumice, and hot gases, often followed by pyroclastic flows. This combination of a layered structure and highly explosive eruptions makes them the most dangerous type of volcano, which is why that description fits best.

They aren’t shield volcanoes, which are broad, gentle sloped constructs built from low-viscosity basalt flows that erupt quietly. They aren’t limited to basaltic lava, since composites typically involve more viscous magmas such as andesite or rhyolite. And they aren’t restricted to underwater settings; many composite volcanoes form on land at subduction zones.