The expanding Earth theory holds that the original Earth was much smaller and that ocean basins were lacking then. While the theory has largely been debunked in recent years, new research from GPS and other space geodetic techniques indicates that the Earth may actually be expanding at present at about 0.1–0.4 mm/yr. In addition, new evidence showing that deep mantle plumes rise all the way from the core–mantle boundary sheds light on a possible expansion mechanism.