How do shield volcanoes compare with stratovolcanoes in eruption style and hazards?

• A. Shield volcanoes: explosive eruptions; Stratovolcanoes: lava flows
• B. Shield volcanoes: high-viscosity magma; Stratovolcanoes: low-viscosity magma
• C. Shield volcanoes: low-viscosity lava and lava flows; Stratovolcanoes: high-viscosity magma and explosive hazards
• D. Both types have identical eruption styles and hazards

Answer: (C)

Magma viscosity drives eruption style and the hazards that follow. Low-viscosity magma flows easily, so eruptions are mainly effusive lava flows that build broad, gently sloped volcanoes. Shield volcanoes are formed by these steady effusive eruptions of low-viscosity lava, allowing lava to travel long distances and create widespread lava plains, with hazards centered on lava inundation and gas emissions rather than violent explosions.

In contrast, high-viscosity magma traps more gases, leading to pressure build-up and explosive eruptions. Stratovolcanoes arise from these higher-viscosity magmas and are characterized by powerful explosions, ejecting ash plumes, pumice, and pyroclastic flows, and they can trigger lahars.

So the best description is shield volcanoes with low-viscosity lava and lava flows, and stratovolcanoes with high-viscosity magma and explosive hazards. If a statement reverses these ideas or claims there’s no difference, it doesn’t fit the observed patterns of eruption styles and hazards.