Final answer:
The lower layer of earth that stores groundwater is called an aquifer, which is essential for providing drinking and irrigation water and plays a significant role in the water cycle.
Step-by-step explanation:
The lower layer of earth that holds groundwater is called an aquifer. An aquifer is a subsurface reservoir of fresh water that can be found in the pores between sand, dirt, and gravel or within the fissures of rocks. This groundwater may flow to surface water bodies such as streams and lakes, or be stored for long periods, sometimes for millennia, in bedrock.
The movement of groundwater plays a key role in supplying drinking and irrigation water through wells, contributing to the natural water cycle, and even in affecting the spread of contaminants within the environment.