Did asteroid strikes during the earth's youth spawn the earliest fragments of today's landmasses?

• Asteroid collisions rocked the earth for much more of its early history than previously thought.

• New evidence reveals that nine major strikes occurred between 3.8 billion and 2.5 billion years ago—the eon during which the planet’s first continents were coming to be.

• A bold, new hypothesis suggests these rogue space rocks were not totally destructive; they might have helped trigger the formation of continents.

Roiling, incandescent magma and boiling gases covered the earth in the wake of its formation 4.6 billion years ago. Regions of this fiery sea eventually cooled enough to crust over, leaving the planet’s first hard rocks floating like slag on the white-hot liquid. But they were nothing more than a thin veneer. The thick roots of terra firma were much longer in the making.

Exactly how—and how quickly—continents arose and grew is a matter of ongoing debate. Scientific wisdom long held that the earth’s inner workings alone drove continent formation. But recent findings have turned the spotlight toward a once heretical idea: that large asteroid impacts played a constructive role as well.

Source : Scientific American (requires subscription)