 Earth 's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years . 71 % of Earth 's surface is covered with water . The remaining 29 % is land mass — consisting of continents and islands — that together has many lakes , rivers , and other sources of water that contribute to the hydrosphere . The majority of Earth 's polar regions are covered in ice , including the Antarctic ice sheet and the sea ice of the Arctic ice pack . Earth 's interior remains active with a solid iron inner core , a liquid outer core that generates the Earth 's magnetic field , and a convecting mantle that drives plate tectonics . 
