I am going to assume the earth has a rocky outer crust that lays atop molten rock, and this goes right around the planet… kind of like the skin of an orange or something, but underneath the skin its all molten rock/lava.
If that is the case (as I am certain it is) why isn’t the crust of the earth flowing around the molten “sphere” of the planet? Why isn’t North America falling south and Antarctica going further North? Or I guess a better question is why aren’t continents moving faster than inches per century?
The Earth’s mantle is not liquid. It is supposed to be about the consistency of playdoh in most places, with some areas that are a bit less viscous. Down deep, it’s almost solid due to the extreme pressure. Even if it was liquid, it would still exert a lot of drag on the floating landmasses on top of it.
The crust of the Earth (as individual plates) is below oceans as well as land. Everything is already jammed up together (continental and ocean plates) so that the continents can’t just drift around willy-nilly. Where 2 plates are colliding, one is going up over the other which is getting pushed under (subduction). The process is slow. Continental plates are heavy and the mantle is viscous.
Lava from volcanoes can move quickly, but that is a localized explosion (magma moving from high subsurface pressure to low atmospheric pressure).
The earth core/mantle/crust solid/liquid/solid is simular to how a torque converter in a automatic tranny works. Basically the force is transmitted from one solid through the fluid to the other solid. The 2 can spin at diffrent speeds but will eventually sync.
I recall doing a calculation in a geophysics class, and the viscosity we got for the asthenosphere (which is the closest any part of the mantle comes to being a true liquid) was about the same as glass.
Continents are still rebounding from the retreat of the glaciers 10k + years ago. This wouldn’t be true if the mantle were less viscous.
