What is the best description of weathering? a. breakdown of rocks through mechanical or chemical processes. b. when rocks layers from horizontally. c. building up earth's surface through deposition. d. processes that make it difficult to determine the age of rocks.

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.