Usually in the ocean, the ground cracks up and earthquakes are a big cause in this. When the floor breaks, it lifts and causes large waves sometimes eventually leading into tsunamis. Earth movement is something that happens usually when the the core of the Earth changes just by the slightest temp causing heat to rise from the center and to the top and crack the ground. Now if your talking about the movement in Earth as in Rotation then that has to do with how there’s no gravity in space and how it’s in orbit with the rest of the planets around the sun
Sorry for the paragraph lol