In an episode of the '60s Superman cartoon, there was a shot of Superman basically doing a handstand as he moved the Earth, which always brings up the question as to whether anyone could move a planet (rather than burrow into it) no matter how strong he was.
A handstand? Why couldn't he just push down with his legs?
In
another thread I referenced
Superman #220 (October 1969). In that story, Superman used his heat vision to scorch a large plot of ground to give him a firm place to push against. I guess it was lucky he didn't need to push against the ocean floor. Then he flew at the ground shoulders first, and his impacts were felt all over the Earth.
Personally, I'm not sure where to draw the line on Superman's strength. Moving the Earth--or even the Moon--seems to be too much. But I do think he should be able to catch a falling passenger jet while he is flying, or lift a supertanker from the sea and carry it to port.