The Pacific tectonic plate and the South American tectonic plate are slowly moving away from each other. Over thousands of years, which of the following natural structures might be formed at this plate boundary?

At the boundary between the Pacific tectonic plate and the South American tectonic plate, which are moving away from each other, the natural structure that might be formed is:

- **A ridge**, which is a structure formed due to magma coming out of the mantle and hardening.

When tectonic plates diverge, magma rises from below the Earth's surface to fill the gap, creating a mid-ocean ridge or a rift, depending on whether the plates are oceanic or continental. In contrast, the other options such as mountains, faults, and volcanoes would typically be associated with convergent plate boundaries, where plates collide or interact in different ways.