Rock & Gem

Just How Old are the Continents?


According to convention­al wisdom, Earth’s first stable granitic continents, or cratons, rose above dense basaltic oceanic crust 2.6 billion years ago. Or did they?

Geologists believe Earth was formed by cosmic dust and debris 4.54 billion years ago as a molten sphere. As that sphere cooled and coalesced, features still recognizab­le today began to emerge, such as a global ocean. From that ocean emerged cratons, which geologists have long dated to 2.6 billion years ago.

Recently, a team of geologists led by Priyadarsh­i Chowdhury of Monash University has reason to question that wisdom. After studying and dating rocks from India, the team published findings in the journal Proceeding­s of the National Academy of Sciences that provide a much earlier date for craton formation of 3.3 to 3.2 billion years, around 700 million years earlier than previously estimated.

Why is this date important? According to Chowdhury, “This was the first step toward making the earth more habitable.” In other words, cratons mark the first step toward mankind and the earth as we know it today.

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