Comment by shadowgovt
6 days ago
I remember there being some modeling done to determine whether the Theia impact blew a chunk off Earth or basically re-liquified the planet. If I recall correctly, the resulting hypothesis was that the thermal load would have re-melted at least the crust (evidence for this was stacking of density in the moon, suggesting it formed out of a basically completely-liquified ball, which would have implied the crust was also liquified).
There is some interesting evidence suggesting the deeper layers remained intact, in the form of a region under the Pacific that might be the impact scar. It's an inexplicably-dense zone that causes hot-spots at its corners resulting in increased surface volcanism, like how the edges of a leaf burn before the middle in a fire.
... but on the surface? Yeah, no hiding place.
Would oceans have remained at all?
According to physics simulations, the atmosphere was composed of vaporised rock for several centuries after the impact until it cooled down below 1000 degrees. The entire surface was magma. https://en.wikipedia.org/wiki/Synestia
No; I don't remember the article saying specifically but I would assume if there is no solid land left, there is no liquid water left either. Water molecules would have been blasted into the "crust soup" and eventually re-condensed into gaseous water and eventually liquid water via atmospheric regeneration after the surface settled down a bit (because the chemicals that could be gaseous would have tended to float to the top of the soup as it settled down).