A broad volcano formed by layers of cooling lava is called what?

A broad volcano formed by layers of cooling lava is called what?

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

Answer: (A)

Lava viscosity matters for the shape of a volcano. When lava is low in silica, it flows easily and can spread out over large areas before it cools. Repeated lava flows then pile up as many thin, solid layers, creating a broad, gently sloping mountain. This is described as a basic (basaltic) volcano in many contexts. The other terms don’t describe volcanic forms: an artesian aquifer is groundwater under pressure, the asthenosphere is a mantle layer, and bioethanol is a biofuel. So a broad volcano formed by layering of cooling lava fits the idea of a basic volcano.

Lava viscosity matters for the shape of a volcano. When lava is low in silica, it flows easily and can spread out over large areas before it cools. Repeated lava flows then pile up as many thin, solid layers, creating a broad, gently sloping mountain. This is described as a basic (basaltic) volcano in many contexts. The other terms don’t describe volcanic forms: an artesian aquifer is groundwater under pressure, the asthenosphere is a mantle layer, and bioethanol is a biofuel. So a broad volcano formed by layering of cooling lava fits the idea of a basic volcano.