Similar to Mars. The deepest oceanic depth is 36000 ft, the highest mountain 29000 ft - the Earth has a diameter of 7900 miles, so the surface features are mere ripples by comparison.
Mass produces gravity that produces internal pressures and volcanism to mold planets into spherical shapes. Gases from combustion create atmosphere. Chemical makeup o volcanic gases make H2O for oceans and so we have it.. Earth. Why no other? Methink we do have ammonia oceans and oceans not of water on other worlds though.
This post was edited by O-uknow at April 30, 2017 10:52 PM MDT
Planets and larrge moons are spherical due to gravitational forces which acted upon them when they were accreting and thus still molten. Volcanism has nothing to do with it, that affects surface features only. The heavier bodies also attracted lighter gases. Jupiter has an atmosphere many thousands of times denser than Earth's, no tectonic activity whatsoever.
Jupiter is primarily gas, albeit with much of it in the liquid or solid state.
What the Earth might look like without water or atmosphere is an interesting question. The answer depends on which assumption you choose: it lacked both right from the start, or it had both but lost them.
If it had never had water or air, there would have been no erosion of the earliest continents, which probably started as more or less flat, featureless granite plains. (The surrounding ocean floor, away from the Continental Shelves, is of basaltic rock.) So no sedimentary rock.
Would there would still have been much tectonic, volcanic and seismic activity? Possibly.
Slartibartfast 