Some years ago, I was asked by a friend to accompany him on a visit to a site in Saratoga Springs, New York, where we were to witness the activities of a gen-u-wine geomancer. I had never heard of a geomancer before. If you don’t know what one is, be happy. If you do, you have my sympathies. The thing is, this geomancer wanted to geomance (I just verbed his noun) with these rocks in or near a place called Lester Park. Now, if you’ve heard of Lester Park you may be thinking you know which rocks this guy wanted to commune with, but you are probably wrong. Lester park has some of the most famous rocks in the world, and then it’s got these other rocks. The other rocks are geologically interesting. They are small formations, ranging from the size of a van to the size of a cottage sticking up out of an otherwise flattish landscape. It appears that the parent rock of the area, which I take to be some kind of schist or otherwise highly metamorphosed stuff, had some force act on it to cause vertical parts to be slightly more resistant to erosion and thus stick up above the other rock. Personally, I think it might be diagenesis concentrated along joints or fissures of some kind, where hot gasses were allowed to mingle with rock under great pressure, deep below the surface of the earth in the depth of time. The geomancer thought it was energy flux lines passing through the earth and linking these rocks to Buddhist Temples in Asia. I came to my conclusion using the old fashioned scientific technique of guessing. He came to his conclusion using a bent coat hanger.
Anyway, not far from this spot, in Lester Park, one finds this rock:
This is “stromatolite.” Blue-green algae, a.k.a. bacteria, generates a “biofilm” that probably has a number of purposes, including managing moisture and protecting the cells from UV light. You know this stuff. If you leave water in an open glass long enough you’ll get a slimy surface on the inside of the glass. Perhaps you get a dark gray (or some other color) film in your toilet bowl, and certainly, there is a fuzzy slimy coating in the reservoir in the back of your toilet. Go to a lake and look at the stuff forming on the rocks that isn’t a plant. Most of that stuff is biofilm.
Cyanobacteria, Cyanophyta, blue green algae, blue-green amd bacteria are all different names for the same phylum of bacteria. Other bacteria make biofilms as well, but the cyanobacteria (or something very much like cyanobacteria) were at one time the dominant organism on the planet, and lived on the surfaces of anything covered with enough water on a regular basis to make it possible to stay wet, but not enough water to shade it from the sun. These are the organisms that altered our atmosphere to be oxygen bearing instead of oxygen poor, according to most prevailing theories of early life on earth.
Before things like snails (snails are only the most modern form of creatures like this) cynobacteria living in shallow seas developed bioflims over long periods of time, and these biofilms built up, and trapped bits of sediment, to form stramotlites. Here’s some more pictures:
So, in case it isn’t already obvious, this is the cool think about stromatolites: They exist only in ancient contexts, and as fossils, but are the outcome of a process that is very much current, but because of the creatures that eat the algae and the bioflims, stromatolites stopped forming very very early in the history of life.
Almost. In fact, stromatolites still form and probably have formed off and on, here and there, under certain rare conditions. For example, in Shark Bay, Australia. This is an arid patch of ocean partly embayed on the west coast of Oz where evaporation is sufficiently rapid that the water is hyper-saline. The hyper-saline conditions make it impossible for snail-like cyanobacteria-eaters to be abundant. Therefore, there are active “living” stromatolites there.
I came across the above photos that I had taken on that day, years ago, with the geomancer. Thought you might enjoy them.
Here’s some more info on Lester Park: Lester Park (New York State Museum)