What key element differentiates a cavern from a cave?

The key element that differentiates a cavern from a cave is that a cavern is an underground environment where natural light is visible at least part of the time. This characteristic is crucial because it defines the accessibility and safety considerations for divers and explorers. In a cavern, the presence of light typically means that the entrance or an opening to the surface is nearby, allowing for easier navigation and an understanding of the area without complete darkness. This also impacts diving practices, where light visibility can help in guiding divers and ensuring safer conditions.

On the other hand, other descriptions such as size comparison, formation by tectonic activity, or the presence of water do not accurately capture the distinction. A cavern can be smaller or larger than a cave; its size is not a reliable differentiator. While tectonic processes may play a role in the formation of both environments, they are not exclusive to caverns. Additionally, water is often present in both types of formations and does not serve as a defining feature to differentiate between them.