a mechanism based on the presence of surface water has the advantage of being able to readily explain the absence of plate tectonics on other terrestrial planets in the solar system.
My mental model of why we have surface water and plate tectonics is that the planet’s molten core causes both.
The molten core causes the magnetosphere, which deflects a bunch of stuff that would otherwise strip the atmosphere and water off the surface. It probably helps keep the surface at a temperature where water is liquid.
The molten core also moves around and contributes to plate tectonics.
Someday in the distant future, once the core is cooled, Earth will look kind of Mars-like—no liquid surface water and no plate tectonics.
This isn’t to diminish the potential role of water in the details of how plate tectonics works, but rather to suggest that “tectonics because water” seems less logically sound than “water and also tectonics because of planet’s core”.
My mental model of why we have surface water and plate tectonics is that the planet’s molten core causes both.
The molten core causes the magnetosphere, which deflects a bunch of stuff that would otherwise strip the atmosphere and water off the surface. It probably helps keep the surface at a temperature where water is liquid.
The molten core also moves around and contributes to plate tectonics.
Someday in the distant future, once the core is cooled, Earth will look kind of Mars-like—no liquid surface water and no plate tectonics.
This isn’t to diminish the potential role of water in the details of how plate tectonics works, but rather to suggest that “tectonics because water” seems less logically sound than “water and also tectonics because of planet’s core”.