November 2008

As old as the hills

By M. Kerawala

To the untrained eye, the world’s oldest rocks seem to form just another placid northern landscape.

Questions about how the world came to be have preoccupied humankind since time immemorial. The answers are usually elusive either because the quest is speculative or because time itself veils the truth.

Geoscientists in Canada recently parted that veil when they discovered the world’s oldest known rock. Jonathan O’Neil and Don Francis of McGill University, Ross Stevenson of the Université du Québec à Montréal and Richard Carlson of the Carnegie Institution in Washington, D.C. used samarium and neodymium isotope analysis to date rocks in the Nuvvuagittuq greenstone belt in northern Quebec. They turned out to predate the current record-holder by 300 million years. At 4.28 billion years old, the rock dates back almost to the origin of the solar system. The news caused a stir in the scientific community when the team published its findings in the September 26, 2008 issue of the journal Science. These weather-beaten geriatric rocks are expected to help geoscientists answer fundamental questions about the formation of the earth’s crust and the forging of its terrain.

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