How old is the Earth?
The current best estimate for the age of the Earth-Moon-meteorite system is 4.51 to 4.55 billion years, with a confidence of 1% or better (Dalrymple, 2001).
The solar nebula cooled to the point at which solid matter could condense by ~4.566 billion years, after which the Earth grew through accretion of these solid particles, the Earth's core developed, and the Moon formed by ~4.51 billion years (Dalrymple, 2001; Allegre and others, 1995; Halliday and Lee, 1999; Tera and Carlson, 1999; Tera, 1981; Patterson, 1956).
The age of the Earth has been known reasonably well since the 1950s, when geochemist Clair Cameron Patterson of CalTech determined it to be 4.550 billion years +/- 70 million years. This age was based on isotopic dating of 5 meteorites and a representative sample of modern Earth lead from a Pacific deep-sea sediment, all of which plot along a linear isochron on a graph of 207Pb/204Pb versus 206Pb/204Pb (Patterson, 1956). Patterson built upon earlier work by Arthur Holmes, E.K. Gerling and F.G. Houtermans (see Dalrymple, 2001; Lewis, 2000). More recent work has generated ages within Patterson's margin of error.
References and suggested reading
Allegre, C.J., Manhes, G., and Gopel, C., 1995, The age of the Earth: Geochimica et Cosmochimica Acta, v. 59, p. 1445-1456.
Dalrymple, G.B., 1991, The age of the Earth: Stanford, California, Stanford University Press, 474 p., ISBN 0-8047-2331-1.
Dalrymple, G.B., 2001, The age of the Earth in the twentieth century -- a problem (mostly) solved, in Lewis, C.L.E., and Knell, S.J., [editors], The age of the Earth -- from 4004 BC to AD 2002: The Geological Society, London, Special Publication 190, p. 205-221, ISBN 1-86239-093-2.
Dalrymple, G.B., 2004, Ancient Earth, ancient skies -- the age of Earth and its cosmic surroundings: Stanford, California, Stanford University Press, ISBN 0-8047-4933-7.
Faure, G., 1986, Principles of isotope geology [2nd edition]: New York, John Wiley & Sons, 589 p., ISBN 0-471-86412-9.
Halliday, A.N., and Lee, D.C., 1999, Tungsten isotopes and the early development of the Earth and Moon: Geochimica et Cosmochimica Acta, v. 63, p. 4157-4179.
Lewis, C., 2000, The dating game -- One man's search for the age of the Earth: Cambridge, UK, Cambridge University Press, 253 p., ISBN 0-521-79051-4.
Lewis, C.L.E., and Knell, S.J., [editors], 2001, The age of the Earth -- from 4004 BC to AD 2002: The Geological Society, London, Special Publication 190, 288 p., ISBN 1-86239-093-2.
Patterson, C.C., 1956, Age of meteorites and the Earth: Geochimica et Cosmochimica Acta, v. 10, p. 230-237, http://thermo.gg.utk.edu/courses/Ge475/Patterson.html
Richardson, S.M., and McSween, H.Y., Jr., 1989, Geochemistry -- pathways and processes: Englewood Cliffs, New Jersey, Prentice-Hall, 488 p., ISBN 0-13-351073-5.
Tera, F., 1981, Aspects of isochronism in Pb isotope systematics -- application to planetary evolution: Geochimica et Cosmochimica Acta, v. 45, p. 1439-1448.
Tera, F., and Carlson, R.W., 1999, Assessment of the Pb-Pb and U-Pb chronometry of the early Solar System: Geochimica et Cosmochimica Acta, v. 63, p. 1877-1889.
The information on this page was written and approved by the faculty of the Geology Department at Baylor University.