I knew I was right.
Dang.
I think where my thought was actually going was to how critical the surface area of the ocean is to maintain temperatures and other climate factors. A change of 10% in total water volume could have drastic effects on climate. It seems odd that the ocean has always maintained vital amounts of water. I know that we are constantly losing water to Outerspace and that most of the earths atmospheric hydrogen is tied up in water, so how does the new water form? There is a long list of conditions that have to be met for life to exist. Just the climate aspects of this list must be fascinating…
Maybe the vast majority of rocky parents in the habitable zone are either completely dry or completely covered with water. But if our world hadn’t developed both land and seas, we wouldn’t have evolved to ask this question.
True. We’d be asking: “Why is there water everywhere?” or “Why isn’t there any water?”
Maybe. My guess is that it would very hard for advanced life to develop on a dry planet, and very difficult for a technological civilization to develop underwater. Perhaps the extreme rarity of mixed land-sea worlds like ours is one solution to Fermi’s Paradox.
Because if it did, Kevin Costner would make more terrible movies?
He’d make the same movie, but it would just be called “World”.
Is this a fact? All of the material and elements here originally came from space, but does the planet shed material back into space?
Tangential to the OP question - if there were no water on Earth, would we still have plate tectonics?
Yes, it is. All planets shed material into space, it is called atmospheric escape; depending on the planet, its atmosphere and temperature it will be different materials. And at the same time all planets accrue material by meteorite bombardment. Mostly micrometeorites, shooting stars and the like, and the occasional big asteroid or comet, more frequent in the distant past.
IANA geophysicist. But plate tectonics are driven by the internal heat of the Earth’s core.
So if we magic-wanded the water away today that process would continue much as it does now for the long-term future. The weathering of the formerly above water sruface would slow down, but that’s a different and much smaller process.
Now if we assume instead Earth never had much water we’d have to talk about how the rest of Earth’s formation was different. Which differences might cause the core heat to be different now.
Overall I’d bet core / mantle convection and surface tectonics are pretty much a given on any rocky / metallic body. The only question is how big the body is and therefore how long it takes for the core to finish cooling and the power source to die out. It already happened on Mercury, the Moon, and Mars. Not yet for Earth, and won’t for a long time coming.
Thanks for those responses. Ignorance fought.
Perhaps, but perhaps not. It used to be assumed that water played an important role as lubricant for plate tectonics, i.e. without water there would be no movement of the plates, but newer data seem to contradict that. The jury is still out, it seems.
Fact is that other planets in the Solar System do not have plate tectonics, with the possible former exception of Mars.
As best current science can tell us, Venus has vulcanism now and Mars did but does not now. AFAIK whether there are/were tectonics on those bodies is TBD.
Definitely not my area of expertise and I look forward to any cites or expert input.
It may well be that tectonics requires an unusually hot interior for an unusually long time. Hotter than you’d get from radioactive decay plus the heat of original accretion. The kind of heat you’d only get from a planet that experienced a truly monster collision rather late in its formation. Of which the Earth/Moon system is the only example in our system.
Arguably, given static demand, the RE lobbyists would want more water coverage. Artificial scarcity is wonderful for raising property prices. Real scarcity has a similar effect.
Now, where DID I put that turkey baster …
Tectonic plates, Bekkers, hon.
Teutonic plates have to do with hats having horns and iron brassieres.
~VOW
I blame autocorrect.
I thought it was pure genius-osity. 
Water doesn’t cover the entire earth because it’s too hot. When frozen water covers the surface in a lot of places it melts and runs off.
Now that is a really cool and novel take on the situation. Thank you.
Yes.
It’s the same with chocolate.