![]() ![]() Multiplied over millions of years, enough oolitic sand can accumulate to cover expansive beaches such as those found in the Bahamas. Slowly, this process creates a grain of sand. These microbe biofilms excrete minerals, and as each new layer envelops the growing core, the old one dies off, leaving a calcified layer behind. Beneath the polished surface of each ooid are concentric layers of calcium carbonate that look strikingly similar to tree rings when viewed under a microscope.Īccording to Burne’s new research, these nested mineral layers are deposited one by one by microbe communities that cling together and grow in a slimy film around the core. ![]() The word ooid is derived from the Greek word for egg, and up close the oolitic sand looks like an endless sea of tiny eggs. “We have proposed a radically different explanation for the origin of ooids that explains their definitive features,” says Burne. While some scientists suspect that ooid growth is driven by the chemical process of minerals precipitating out of the water, new research led by geologist Bob Burne of Australian National University adds evidence to a competing hypothesis that microbes are at the root of the process. This initial nugget forms the core onto which dissolved minerals are laid down, eventually growing into tiny granules known as ooids. Oolitic sand begins as a speck-maybe shrimp feces or a tiny shell fragment-suspended in shallow, roiling water. On the shores of the Bahamas, Great Salt Lake in Utah, and a handful of other locations, oolitic sand is built up, layer by layer, by a process that remains somewhat mysterious. But one peculiar type of sand bucks this trend: instead of eroding, it grows. For instance, a massive boulder is weathered by the elements and breaks down into millions of tiny flecks, or a reef is chipped away and extruded by the hard-toothed, coral-chomping parrotfish. ![]() Share this articleīecoming a grain of sand is a long, erosive process. ![]()
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