Suppose you drained the ocean without any repercussions caused by the transport and allocation of that much water. Looking at land like the ring of fire or deep sea thermal sites, would the crust remain thin enough for heavy volcanic activity? Or would it thicken up and cause that activity to cease?
For some context, there was an impact on this planet in its deep geological history that somewhat changed the planetary shape and rotation, and over time, the ocean was periodically locked in glacial ice (or was thrown into space on impact, idc). Much of the modern world, for lack of liquid water, is open landscape. I want to know if there will be large patches of volcanic land in these areas far rivalling Iceland and the like due to plate thickness. I'm really hoping for vast nation-sized Mordor locations but they aren't necessary. Miniscule activity sites ala Yellowstone are sufficient. I am willing to bet that the impact may have also ruptured a portion of the crust outward from its crater. It wasn't a terribly traumatic impact (as in the planet probably had an atmosphere ported in later but it's still in one piece), the important part is that it have the planet a nigh undetectable hump kind of like Earth. I am also willing to skip the impact, have the oceans disappear/hump appear some other way, they're not important details.