1746 - Jean Etienne Guettard presents the first mineralogical map of France to the Academie des Sciences.
1760 - John Michell suggests earthquakes are caused by one layer of rocks rubbing against another
1776 - James Keir suggests that some rocks, such as those at the Giant's Causeway, might have been formed by the crystallisation of molten lava
1779 - Comte de Buffon speculates that the Earth is older than the 6,000 years suggested by the Bible
1785 - James Hutton presents paper entitled Theory of the Earth - earth must be old
1799 - William Smith produces the first large scale geological map, of the area around Bath
1809 - William Maclure conducts the first geological survey of the eastern United States
1830 - Sir Charles Lyell publishes book, Principles of Geology, which describes the world as being several hundred million years old
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
1903 - George Darwin and John Joly claim that radioactivity is partially responsible for the Earth's heat
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
1911Arthur Holmes uses radioactivity to date rocks, the oldest being 1.6 billion years old
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
