Where is intense geologic activity most concentrated?

Intense geologic activity is most concentrated at plate boundaries due to the interactions between tectonic plates. These boundaries are where the Earth's lithosphere is divided into large sections that float on the semi-fluid asthenosphere beneath. As these plates move, they can converge, diverge, or slide past one another, leading to various geological phenomena.

At convergent boundaries, where plates collide, one plate may be forced beneath another in a process called subduction, leading to volcanic activity and the formation of mountain ranges. At divergent boundaries, where plates move away from each other, magma rises to create new crust, often resulting in mid-ocean ridges and seismic activity. Transform boundaries, where plates slide horizontally past each other, also experience frequent earthquakes.

Therefore, the concentration of geologic activity at plate boundaries is a direct result of these dynamic plate interactions, making it the correct answer.