What can a confined aquifer be described as?

A confined aquifer is characterized by its location between layers of impermeable rock or sediment, which restricts the flow of water. This confinement creates pressure within the aquifer, allowing water to be stored under pressure. When a well taps into a confined aquifer, the water might naturally rise to the surface due to this pressure, a phenomenon known as artesian flow.

The other options do not accurately describe a confined aquifer. For instance, the notion of containing only saltwater does not apply because confined aquifers can hold freshwater or saltwater, depending on their geological setting. Similarly, being fully exposed to the atmosphere would refer to an unconfined aquifer, which does not have such impermeable layers above it. Lastly, a direct connection to surface water is typical of unconfined aquifers, where water can directly recharge from precipitation or surface sources. Thus, the defining feature of a confined aquifer as being encased between layers of impermeable rock is key to understanding its unique properties and behavior in hydrology.