What boundary occurs when tectonic plates move away from each other?

• A. Transform boundary
• B. Divergent boundary
• C. Convergent boundary
• D. Subduction boundary

Answer: (B)

When plates move apart, the boundary that forms is a divergent boundary. As the rocks pull away, a gap opens and magma from the mantle can rise to fill it, cooling to create new crust. This process is why mid-ocean ridges appear in the oceans and why rift valleys form on continents, with seafloor spreading adding new material to the crust. Earthquakes can occur at these boundaries, and volcanic activity is common as magma intrudes to fill the space. In contrast, boundaries where plates collide or slide past each other produce different features: convergent boundaries bring together and often subduct, while transform boundaries involve horizontal sliding.