Scientists have discovered that the Earth’s crust is literally dripping through some spots below it and into the deeper parts of the planet. It heats up, gets all gooey, and drips through open spots. You can even tell where this has happened. Apparently, when that heavy, liquid earth drops off the bottom of the crust, the crust bounces back up a bit and creates a wide bulge above ground.
Think of it this way. Imagine a trampoline with a 25 pound weight attached to the bottom. Then imagine it detaching and falling off. As it detaches, the trampoline surface bounces up. Same idea.
One spot that researchers found is dropping by almost an inch per year or around 7 or 8 feet every hundred years.
Will humans all be living underground in the next millennium? Probably not because of this. Earth collects about 5,000 tons of space dust on the surface every year.