Outline the difference between effusive and explosive volcanic eruptions, and their typical hazards.

• A. Explosive eruptions primarily emit lava flows.
• B. Effusive eruptions primarily emit lava plumes.
• C. Explosive eruptions generate lava flows only occasionally.
• D. Effusive eruptions emit lava flows; hazards include lava paths.

Answer: (D)

Effusive eruptions involve magma that flows steadily to the surface as lava, forming lava flows that travel downslope or across the landscape. The key hazard is the lava itself moving along paths, destroying anything in its way and shaping new lava fields over time.

Explosive eruptions, by contrast, are driven by rapid gas expansion in more viscous magma, blasting material into the atmosphere as ash clouds, pumice, and bombs, and often generating dangerous pyroclastic flows. Hazards here include ash falls that affect health and aviation, pyroclastic surges that devastate nearby areas, and related impacts like lahars when ash mixes with water.

The best choice captures the essential difference and ties it to a primary hazard: effusive eruptions emit lava flows, with hazards including lava paths. The other statements mix up what each type primarily emits and what hazards they produce.