Quote - Sounds logical, but have you ever watched figure skaters or have wondered what the little clumps of lead on a wheel rim are for?

If you look only at the skater you will see that he changes his momentum, the same with acrobats and cats. But the skater is not isolated in the Universe, there is the reaction of the ground, so if you consider the whole system, skater + ground, the total momentum has not changed.

In an earthquake, if you look alone at the piece of soil that moved you will see that the momentum has changed, but the soil is not isolated, you have the other part of the soil that have also moved and changed its momentum, the tsunami wave also had acquired momentum. If you summ the momentum of all parts, one piece of soil, the other piece, water and all other parts invvolved, the total momentum has not changed and so the whole momentum of the planet Earth remained unchanged.

The only way to change the momentum of Earth is to apply an external force such as collision with other planet, asteroid, comet or gravitational pull by bodies external to the Earth (Sun, Moon, planets, asteroids, comets)

Stupidity also evolves!