Seas and oceans make up roughly what proportion of the earth's surface?
Earth and some of its mass merged with Earth. Between approximately 4.1 and , numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth. Earth's atmosphere and oceans were formed by volcanic activity and outgassing. Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets, and comets. In this model, atmospheric "greenhouse gases" kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity. By , Earth's magnetic field was established, which
Spherical Earth would likely crack, heat up, liquefy, and re-form into a roughly spherical shape. On a disc strong enough to maintain its shape, gravity would not pull downward with respect to the surface, but would pull toward the center of the disc, contrary to what is observed on level terrain (and which would create major problems with oceans flowing toward the center of the disk). Ignoring the other concerns, some flat Earth theorists explain the observed surface "gravity" by proposing that the flat Earth is constantly accelerating upwards. Such a theory would also leave open for explanation the tides seen in