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
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