1837 - Louis Agassiz begins his glaciation studies which eventually demonstrate that the Earth has had at least one Ice Age
1862 - Lord Kelvin attempts to find the age of the Earth by examining its cooling time and estimates that the Earth is between 20--400 million years old
1907 - Bertram Boltwood[?] proposes that the amount of lead in uranium and thorium ores might be used to determine the Earth's age and crudely dates some rocks to have ages between 410--2200 million years
1960 - Harry Hess[?] proposes that new sea floor might be created at mid-ocean rifts and destroyed at deep sea trenches
1963 - F.J. Vine[?] and D.H. Matthews[?] explain the stripes of magnetized rocks with alternating magnetic polarities running parallel to mid- ocean ridges as due to sea floor spreading and the periodic geomagnetic field reversals