Your diagram leaves out minerals that get trapped in sediments and then swallowed in subduction zones. A prime example of the former is the massive salt deposits under the Mediterranean seafloor. They were form when tectonic movements closed the Strait of Gibraltar and the Mediterranean dried up. By the time it refilled, much of the salt was covered with non-salty sediments, so it could not be dissolved again. Because of plate tectonics, this pattern has been played out frequently in the Earth’s long history. And consequently, the ocean’s salinity has varied.

--

Geognosticator

Love podcasts or audiobooks? Learn on the go with our new app.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store