In a rough-and-tumble wonderland of plunging canyons and towering buttes, some of the still-raw bluffs are lined with soaring, six-sided stone columns so orderly and trim, they could almost pass as relics of a colossal temple.

New research indicates that one of the largest fresh-water floods in Earth's history happened about 17,000 years ago and inundated a large area of Alaska.

By York, Richard; Clark, Brett Over 500 million years ago, Pikaia, a two-inch-long worm-like creature, swam in the Cambrian seas. It was not particularly common, nor in anyway would it have appeared remarkable to a hypothetical naturalist surveying the fauna of the time.