Final answer:
An aquifer is a porous rock that holds water, while an aquitard is an impermeable layer that prevents water flow. A good aquifer consists of permeable materials with high porosity, such as sandstone and limestone. A good aquitard is made up of impermeable materials like shale or un-fractured igneous or metamorphic rock.
Step-by-step explanation:
An aquifer is a large area of sub-surface, porous rock that holds water. It is an underground reservoir of fresh water that exists in the pores between particles in sand and gravel, or in the fissures in rocks. Aquitard, on the other hand, is a confining layer of impermeable material that prevents the flow of water. A good aquifer is made up of rocks that are permeable and have high porosity, allowing water to flow through them. Sedimentary rocks such as sandstone and limestone are examples of materials that make up a good aquifer. They have abundant spaces between the grains that compose them, creating high porosity and allowing water to be stored and flow through. On the other hand, a good aquitard is made up of impermeable materials that prevent the flow of water. Examples of materials that make up a good aquitard include sedimentary rocks like shale, which are made from tiny clay and silt grains, as well as un-fractured igneous or metamorphic rock.