Geoscience Reference
In-Depth Information
Figure 14.3 Title and abstract of Clair Patterson's 1956 paper on
meteorites and the age of the Earth published in Geochima et
Cosmochimica Acta 10 (1956) 230-237. This paper gained widespread
circulation and the findings it reported were rapidly accepted by the
scientific community. In this paper Patterson's first name is spelt 'Claire',
but throughout his later life he dropped the 'e'.
meteorite from his home state of Iowa and the Modoc meteorite from
Kansas, were stony meteorites which contained small glassy spheres
called chrondrules, while another stony meteorite, the Nuevo Laredo
meteorite from Mexico, was selected because it lacked chondrules
(achrondrite). All produced ages close to 4,500 million years: Forest
City 4.500; Nuevo Laredo 4,600; and Modoc 4,400. In 1956 Patterson
published his classic paper (Figure
14.3
) that reported on these ages and
added another derived from the Henbury meteorite of Australia
(Figure
14.2
). He plotted the lead ratios for these meteorites and they
formed a line or isochron whose slope gave an age of 4,550 million
years. He noted that his uranium/lead dates were confirmed by col-
leagues including John Reynolds and Jerry Wasserburg a year earlier
using the potassium/argon method. Crucially, he added the lead ratio
for a modern marine sediment and this also plotted on the isochron,
thus proving that the lead in meteorites and terrestrial material were
one and the same age. Consigned to history were the estimates of
3,000 million years based on terrestrial lead.
The Earth is 4,550 million years old.
