Assertion: aquifer | /r/HasProperty | gravel
Facets:
Source sentences:
text: Aquifers are underground layers of porous and permeable rock or unconsolidated sediment, such as sand and gravel, that hold water.
text: Aquifers can be either consolidated rock (such as sandstone) or unconsolidated (such as the sands and gravels that make up the High Plains aquifer.