The Artifact Redux: Stone Mushroom Clouds

see the shallows up close. Down below, there are hundreds of strange, bulbous mineral formations peeking up over the water line or sitting just below it. It's hard to describe exactly what they look like. Black stone broccoli perched upright in the still water, atomic mushroom clouds frozen in place, or dark pebbly brains flocking out of the Indian Ocean.

These are stromatolites. If you stand on the jetty at Hamlin Pool looking out at this army of mineral bulbs, you're getting a pretty close approximation of what most visible life on planet Earth looked like for something like eighty percent of its history. Because while these are mineral formations,

They're not just dead rock, they're alive and growing. Stromatolites are one type from a class of mineral formations called microbiolites, natural stone monuments that are built by microscopic organisms, and not all of them look like the columns of mushroom brain broccoli at Hamlin Bay. Some microbiolites are flat, some are domed, and some form ascending pillars with different shapes

and contours. Though there are lots of microbiolites in the world, there are only a handful of places left where you can find true marine stromatolites growing in the wild. So what makes us stromatallite special. The word stromatallite means layered rock. If you look at a cross section, you can see banded strata within them extremely thin layers of mineral deposition, kind of like a stone puff pastry, with the layers sometimes alternating between light and dark. And these layers actually

tell us something about the process that created them. Stromatallites are built by microscopic organisms like photosynthetic cyanobacteria also known as blue green algae. These are single celled life forms that can be found almost everywhere on Earth, especially in the water. Cyanobacteria like plants, survived by using energy from the sunlight to convert carbon dioxide from the environment into food.

Though cyanobacteria existed for billions of years before the first plants evolved, without them, you never would have been born. As Earth's first photosynthesizers, microbes like cyanobacteria converted the planet's early atmosphere into what it is today by polluting it with their metabolic waste product, which is oxygen. Every animal that ever lived could only evolve because of what the

early photosynthesizers did to the atmosphere. So for billions of years, these microbes dominated planet Earth, changing the composition of the air and leaving behind their stromatolite mineral formations in the fossil record. But to come back to the question about how they form, where do these layers of strata and the stromatalite come from. Microbes like cyanobacteria don't just float

around by themselves. When they're able, they glom onto other micro organisms to form what are known as biofilms or microbial mats. Think of a kind of thin, sticky carpet in which billions of microbes glue themselves both to one another and to an underlying surface with the help of a class of biological cement known as extracellular polymeric substances or e p s s. These microbial mats, being sticky by evolutionary design, don't just stick to the underlying substrate.

They also act kind of like a glue trap, catching hold of tiny grains of sediment and sand that wash over the surface of the mat due to the tide or other mechanical forces. Over the years, layer by layer, these sticky mats of biological material trapped sediment and also calcium carbonate harden into solid mineral formations like the columns at Shark Bay, always climbing up higher like the crown of a tree in the forest, to move towards the

sunlight that feeds them. If you look at the history of earth life in the fossil record from roughly three and a half billion years ago until about one billion years ago, stramatallites absolutely dominate the scene, gathering in shallow sea ease and across continental shores around the world. But around a billion years ago, the finally layered stramatallites start to vanish from the geological record, and they've remained rare

until today. What happened to them. There are several possibilities, but one interesting investigation into this question was a study published in in p N A S by Joan M. Bernhardt at All. This study picks up from the observation that at around the same time stramaatellites began to decline in the fossil record, they seem to be replaced with a different kind of microbial matt formation called a thrombo lighte. Whereas stramatolites are layered rocks, thrombo lights are clotted rocks

with a microstructure to match their name. So did most of the world stromatallites become thrombo lights and if so why? The researchers behind this study suggest that thenswer to the question may lie in the evolution of another organism known as foraminifera. Foraminifera, often shortened to four ams, are a type of single celled eukaryotic organism from the Kingdom of life known as the protests. Along with organisms like amibas

and the Plasmodium parasite that causes malaria. You can find for Aminifera throughout the ocean, often in seafloor sediments, where they use amazing and fantastically creepy, shape shifting tendrils called pseudopods to reach out into their surroundings and snatch up food.

For Aminifera build tiny shells for themselves called tests, and they first evolved roughly around the time the stramatallites were declining and the thrombo lights began to rise, so it makes sense to wonder if they had something to do

with the change in Earth's microbial lites. The authors of study wanted to see if the presence of for Aminifera in a living stormatellite would have a noticeable effect on how new mineral layers were accumulated, so they took modern living stormatellites from a place called high Born Key in the Bahamas and seeded them with foams. Some of the test samples were treated with a drug that would inhibit the function of the forum pseudopods, while others were left untreated.

After about six months, they found that the presence of functional forums could absolutely affect the structure of the stormatallites. In samples where the foreams had been drugged, thin layers were visible. In the samples where the forearms were allowed to do their thing, the stramatallites had assumed the clotted structure seen today in thrombolites. Altogether, this is taken as evidence that the forum and if um may have had

something to do with the stormatellites decline. Today, you can only find living stramatallites in special places, usually places with water that has a very high salinity, like evaporating salt water pools and tidal areas. I kept thinking about how in this way stramatollites have something in common with sauerkraut. Lacto fermented foods like sauerkraut and kimchi are made by salting vegetables and packing them down in a wet, anaerobic environment.

The reason the vegetables turn nice and sour instead of simply rotting is that the salty wet conditions in the jar inhibit the growth of microbes and mold that cause spoilage, but allow the growth of salt tolerant lactic acid bacteria. As the lactic acid bacteria thrive, they produce acid as a byproduct of their metabolism, which lowers the pH of the fermentation, further preventing other microbes from surviving and creating

the sour flavors we love. Wild stramatollites today tend to survive in high salinity environments where organisms that would otherwise graze on the exposed mats and eat them up just can't tolerate the salt. Tune into new editions of the artifact Free Wednesday, hosted either by Robert or myself. As always, you can email us at contact at stuff to Blow your Mind dot com. Stuff to Blow your Mind is

a production of I Heart Radio. For more podcasts for my heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.