Which boundary is constructive, characterized by magma pushing up as the plates pull away from one another?

Which boundary is constructive, characterized by magma pushing up as the plates pull away from one another?

• A. Divergent boundary
• B. Convergent boundary
• C. Ridge boundary
• D. Subduction zone

Answer: (A)

Divergent boundaries are the places where new crust is formed. When tectonic plates move apart, the gap allows magma from the mantle to rise and solidify as new rock, effectively pushing the crust upward and outward. This process, called sea-floor spreading, builds new lithosphere and is why this boundary is described as constructive. In contrast, boundaries where plates collide or one sinks beneath the other lead to crust being consumed rather than formed, so they’re not constructive. The surface feature you often hear about with this boundary—the mid-ocean ridge—illustrates the up-and-push of new material as the plates pull apart.

Divergent boundaries are the places where new crust is formed. When tectonic plates move apart, the gap allows magma from the mantle to rise and solidify as new rock, effectively pushing the crust upward and outward. This process, called sea-floor spreading, builds new lithosphere and is why this boundary is described as constructive. In contrast, boundaries where plates collide or one sinks beneath the other lead to crust being consumed rather than formed, so they’re not constructive. The surface feature you often hear about with this boundary—the mid-ocean ridge—illustrates the up-and-push of new material as the plates pull apart.