Why are trenches and island arcs curved?

Trenches and island arcs are curved due to the dynamics of plate tectonics and the interaction of tectonic plates. As oceanic plates subduct beneath continental or other oceanic plates, the curvature arises from the spherical shape of the Earth and the movement of plates along the mantle. The bending of the subducting plate creates a trench, while the resultant volcanic activity forms an arc on the overriding plate, leading to their characteristic curved shapes. This curvature reflects the complex interplay of forces at play in the Earth's lithosphere.