GEOLOGY

Detailed explanation-1: -An estuary is an area where a freshwater river or stream meets the ocean. When freshwater and seawater combine, the water becomes brackish, or slightly salty.

Detailed explanation-2: -Ocean water contains minerals diffused in water. Examples: common salt, magnesium, and bromine.

Detailed explanation-3: -The minerals come from its contact with the soil. The local geology will determine what minerals leach into the water. In areas like the mid-west with lots of limestone, the water will contain calcium and magnesium.

Detailed explanation-4: -Seawater contains large quantities of valuable minerals, some of which are very scarce and expensive in their land-based form. However, only a few minerals, the ones in high concentrations, are currently mined from the sea.