Which term describes a broad volcano formed by layers of cooling lava?

Which term describes a broad volcano formed by layers of cooling lava?

• A. Basalt
• B. Artesian aquifer
• C. Basic volcano
• D. Asthenosphere

Answer: (C)

The idea being tested is how lava composition and flow behavior shape volcanoes. Basic (mafic) lava has low silica and low viscosity, so it flows easily and spreads over large areas. Each eruption adds another cooled layer, building a broad, gently sloping volcano from successive lava flows. That description fits a basic volcano very well. Basalt is the rock formed from basic lava, which is related but doesn’t name the volcano itself. An artesian aquifer is unrelated to volcanology, and the asthenosphere is a mantle layer, not a volcano. So the best term for a broad volcano built from layered cooling lava is basic volcano.

The idea being tested is how lava composition and flow behavior shape volcanoes. Basic (mafic) lava has low silica and low viscosity, so it flows easily and spreads over large areas. Each eruption adds another cooled layer, building a broad, gently sloping volcano from successive lava flows. That description fits a basic volcano very well. Basalt is the rock formed from basic lava, which is related but doesn’t name the volcano itself. An artesian aquifer is unrelated to volcanology, and the asthenosphere is a mantle layer, not a volcano. So the best term for a broad volcano built from layered cooling lava is basic volcano.