Final answer:
The permeability of a rock layer on which perched water sits depends on its ability to transport fluids. It is determined by factors such as porosity, the size of the open spaces, and how interconnected those spaces are.
Step-by-step explanation:
The permeability of a rock layer on which perched water sits is related to its ability to transport fluids. Permeability depends on factors like the porosity of the rock, the size of the open spaces, and how interconnected those spaces are.
The more porous and interconnected the rock is, the more permeable it will be. For example, sedimentary rocks like sandstone and limestone, which have high porosity and interconnected spaces, make good aquifers and are permeable.
On the other hand, rocks like shale or un-fractured igneous/metamorphic rocks, which lack interconnected spaces, are impermeable and prevent the flow of water.