Say, since the earth is a one piece thing, how could anything on or in enlarge
it unless it came from outer space and was added to the earth?
No. It's definitely not a “one piece” thing.
Each continental land mass is a block of trillions of tons of various rocks, “floating” on the crust below. Because each major block is separate, they can move - which gives us (over hundreds of millions of years) the continental drift and mountain-building we see in many places. If one side of the continental block is moving east, the other is also moving east, but it may be rising up over the other land mass, or falling (going under) the other land mass. Mid-ocean, the crust is differently constructed of usually different rocks, but those rocks masses are either spreading (as in the middle of the Atlantic, or coming together (getting pushed under one another as in the deep rifts of Indonesia.
Either movement (spreading or getting pushed under creates earthquakes. Volcanoes. Lava flows.
Locally, the “continental raft” might be going “up” (sea level apparently receding) or “down” (sea level apparently increasing. I say “apparently” going up or down because it only looks like the ocean level is changing. What's really changing over time is the “land level.”
What the global warming hysterics are claiming is that either Greenland or Antarctica (or both) are going to melt as temperatures rise. (A false assumption, by the way.) Also, they claim that an increase in temperature will cause ocean temperatures to rise, oceans waters to expand, and so ocean levels to go up. Thus “flooding everybody” and killing millions...
(Of course, this became a more popular claim after Katrina. After the democrat LA rulers killed their own people through incompetence and greed.)
Any given island may go up or down as the continental shelf underneath its base goes up and down. Erosion removes land mass. Pumping water (as in Baytown in the mid-70’s) or oil or salt water out of the ground changes elevation.
But. The amount of temperature rise they claim will occur is false. The amount of ice melt is false. The amount of ocean increase is false. The threat is false.