Your answer is radiometric dating
It is true that the famous Mount St. Helens is located in the United States, in Skamania County, Washington, to be more precise.
It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal, and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water
If you're referring to streams/rivers of water that run independently of another source in the ocean these are referred to as "currents" and can be very powerful depending on their location.
