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"Glacial Globe" -- The Discovery Files

The Discovery Files
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Geologists at Harvard University found evidence that sea ice extended to the equator up to 716.5 million years ago, bringing new precision to a "snowball Earth" event long suspected to have taken place around that time.

Credit: NSF/Karson Productions

Audio Transcript:

Third Snowball From the Sun (SOUND EFFECT: splat!)

I'm Bob Karson with the discovery files -- new advances in science and engineering from the National Science Foundation.

(SOUND EFFECT: icy wind) Imagine the earth as a giant snowcone. Seriously, ice-covered at all latitudes. A team led by scientists at Harvard has found direct evidence of a time of nearly complete global glaciation.

Their findings are based on some ancient tropical rocks, (now located in very un-tropical Northwestern Canada). The rocks reveal that some 716-and-a-half million years ago, glaciation left its mark on them. Computer modeling tells us that if sea ice reaches as far south as 30-degrees latitude, the rest of the ocean would freeze over quickly. Based on their magnetism and composition, the rocks the team found were originally located even further south -- at about ten degrees latitude -- bolstering the theory of a "snowball earth."

(SOUND EFFECT: water sounds, ice floe) But there had to be at least some areas of surface water and available sunlight, because of the existence in the fossil record of non-microbial life forms. Scientists are asking whether the stress on these guys may have given evolution a boost and even stimulated the origin of animals, which arose roughly at the same time.

They're also wondering what caused the deep-freeze. And what caused it to stop? (SOUND EFFECT: volcano sounds) One suspect is known volcanic activity, but researchers can't pinpoint whether it was the beginning or end of this c-c-cold chapter in the life of our planet.

"The Discovery Files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at or on our podcast.

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