Which type of aquifer is characterized by being capped by impermeable materials?

A confined aquifer is defined by the presence of impermeable materials, also known as confining layers or aquicludes, above and below it. These impermeable layers restrict water flow in and out of the aquifer, creating a situation where water is under pressure. This pressure can lead to the water in a confined aquifer being trapped and pushed to the surface when tapped by a well, resulting in artesian wells that flow without the need for pumping.

In contrast, an unconfined aquifer does not have such a confining layer above it. This type of aquifer is recharged directly by precipitation that infiltrates the ground and is less confined, allowing water to flow more freely. The distinction between these two types of aquifers is fundamental in hydrogeology, as it impacts their behavior, recharge mechanisms, and the management of groundwater resources.

Since neither a surface aquifer is a recognized classification nor both types of aquifers are characterized by being capped by impermeable materials, the correctness of identifying a confined aquifer as the right answer aligns with its defining characteristic.