Which volcano type is built from low-viscosity mafic lava that creates broad, gently sloped profiles?

Which volcano type is built from low-viscosity mafic lava that creates broad, gently sloped profiles?

• A. Stratovolcanoes
• B. Shield volcanoes
• C. Volcanic domes
• D. Calderas

Answer: (B)

When magma is low in silica and has low viscosity, the lava can flow long distances and spread out over a wide area before it cools and solidifies. That easy, expansive flow builds a broad, gently sloped profile rather than a tall, steep cone. This is why shield volcanoes form—they’re built from these long, lava flows that create a wide, flat-covered shape like a shield.

In contrast, magma that is more viscous resists flow, so eruptions tend to pile material around the vent, producing tall, steep-sided stratovolcanoes. Even more viscous magma tends to ooze out as bulbous, dome-like masses, creating volcanic domes. Calderas aren’t single peaks at all; they’re large depressions left after massive eruptions collapse the上 magma chamber.