Which of the following describes water flowing naturally from the Earth due to an overflowing aquifer?

The correct choice is a spring, which refers to a natural occurrence where groundwater flows to the surface, often due to pressure from an overflowing aquifer. This process typically happens when the water table rises high enough, or when geological formations push the water upwards through the soil and rock layers.

Springs can vary in size and flow rate and are an important part of the hydrological cycle, providing water to ecosystems, rivers, and sometimes human communities. They play a critical role in maintaining the flow of water in streams and rivers, especially during dry periods, and they often support unique habitats due to their consistent water temperature and chemistry.

In contrast, a waterfall refers to the flow of water over a vertical drop, while Old Faithful is a specific geyser known for its regular eruptions of steam and hot water rather than straightforward water flow from an aquifer. A watershed encompasses the land area that channels rainfall and snowmelt to streams and rivers, but does not describe the process of water emerging naturally from the ground. Each term represents a different aspect of water movement and behavior in the environment, but only a spring accurately defines the phenomenon described in the question.