Its all pretty hypothetical stuff and needs to be examined much more carefully to see if the model holds up to further observations. As Mr. Spock would say "All we have is a theory which happens to fit the facts." Still, it is more than we had.
About 1.85 billion years ago, Earth’s now separate landmasses were joined in a single supercontinent. That also means there was one large ocean, says Cannon. Many scientists suggest that the object that slammed into Earth then — probably an asteroid abut 10 kilometers across — splashed down in that ocean, in waters about 1 kilometer deep on the shallow shelf surrounding the supercontinent. Models hint that the tsunami spawned by the event would have been 1 kilometer tall at the impact site and remained at least 100 meters tall about 3,000 kilometers away, Cannon adds.Those immense waves and large underwater landslides triggered by the impact stirred the ocean, bringing oxygenated waters from the surface down to the ocean floor, the researchers propose.
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