A Geophysical Rosetta Stone

Remember the story of Cassandra’s Curse? In one version of the story, the God Apollo was so taken by her beauty that he fell in love with her. And as a token of his love, he gave her the gift of prophesy. Cassandra cheerfully accepted Apollo’s gilt. But she spurned his affections. At first, poor ole Apollo was as broken hearted as can be. And after he had a chance to stew on it for a while, he became just about as angry as a God can get. But after thinking it over a bit, Apollo decided he couldn’t take back his gift of love. Cassandra could keep her gift of prophesy. But he laid a curse on her. And her curse was that no one would ever believe her.

So the essence of Cassandra’s curse was that she would always see the truth clearly. But she couldn’t share it.

Now, in the 21st century, and at the dawn of the information age, new knowledge is in great abundance. There is much to distract. And the ability to see a new truth is no guarantee that anyone is going to even look where you’re pointing anytime soon. Especially if that new found empirical truth runs contrary to some foundation assumptions, and postulates, in the Earth sciences that have gone unquestioned since the early 19th century.

But suppose 21st century technology allowed you to discover an ancient text, written in a language no one had ever encountered before. And you were able to perceive the clues needed to decipher, and read it. What should you do if the form of that text is such that everything you read in it should be treated as empirical fact, and yet the story it tells disagrees with almost everything you have been taught to assume about the uniform, and gradual geohistory, and geomorphology, of the world we live on? Should you try to tell the startling, and catastrophic, truth revealed in that text by shouting it from the mountaintops? Or should you try to teach others to read it for themselves?

I can promise you that, if no one else can read the same truth for themselves, then no one will ever believe it. And it’s Cassandra’s curse all over again. So as for me, I’ll opt for the latter.

One of the best kept secrets in science today is just how good the satellite imagery available through Google Earth has gotten in the past decade of the American southwest, and central Mexico. And the biggest leaps in quality have happened in the past two years. Most of the region is imaged to better than 1 meter per pixel. And the imagery has gotten good enough to assign a directional vector to almost every pixel of the vast sheets of ignimbrite flows. And to read the directions of the fluid emplacement motions like reading a dance chart.

Using Google Earth’s ‘save image’ feature, I made a very large, hi-resolution image map of a large area in the Chihuahuan desert, and it’s vast rivers of melt, consisting of 50 overlapping screen shots seamlessly stitched together with Photoshop. I then had the image map printed out professionally in a format that covers a whole wall. A sheet of clear plastic for an overlay, some markers to draw little arrows to indicate the direction of flow wherever they were discernable, and I had a very high resolution flow map, that would’ve taken decades of difficult surveying, in the middle of some of the most inhospitable terrains on Earth, to produce the old way. A very high resolution flow map like that allows one a forensic perspective of the fluid motions of the emplacement event of those ignimbrites that’s never been available before.

It has always been assumed that only terrestrial volcanism can produce pyroclastic rock.  So the realization that a very large airburst like a larger version of the Tunguska blast of 1908, should be expected to be capable of melting, and ablating, the surface represents a significant paradigm shift in the Earth sciences. Because it describes an entirely new, non-volcanic way to produce Ignimbrite, or ‘Fire Cloud Rock’ It also means that we need to be able to tell them apart.

Fortunately, due to the fact that they have completely different motive forces during emplacement, it turns out that’s not much of a problem.

I don’t want to digress into a discussion about volcanoes. But it’s important at this point to understand the internal structure of these kinds of materials, and how they move during formation, and emplacement. And why it might be easy to get them confused. It’s time to put on your fluid mechanics hat.


From How Volcanoes Work

The extraordinary velocity of a pyroclastic flow is partly attributed to its fluidization. A moving pyroclastic flow has properties more like those of a liquid than a mass of solid fragments. It’s mobility comes from the disappearance of inter-particle friction. A fluidized flow is best described as a dispersion of large fragments in a medium of fluidized fine fragments. A constant stream of hot, expanding gases keeps the smallest of the fragments (ash and lapilli size particles) in constant suspension. This solid-gas mixture can then support larger fragments that float in the matrix.

While in motion, a volcanic pyroclastic flow relies on the pull of gravity for its motive force. The resulting lines of flow will always be downslope, and away from the volcanic vent they came from.

But geo-ablative melt is wind-driven from behind. And since the lines of flow in an unconstrained, and driven, fluid will always be away from the driving force, then when those lines of flow are frozen into a river of melted stone, they become a permanent, reliable, record of the nature of the forces that melted, and moved it.

Thanks to their different motive forces, the two kinds of flows are as visually distinct in satellite imagery as apples, and oranges.

On that fluid motion map, we can assign a directional vector to every pixel at better than 1 meter per pixel resolution with ease. We can read the directionality of the flows, and perceive how it flowed as a fluid with starling clarity. And when we recognize that they are wind driven flows, then they become a proxy for the explosive atmospheric conditions ablating them from the surface, and driving them like the froth, and foam, on a storm tossed beach.

And if each directional vector on our map is thought of as one character of text in a written language of rocks in fluid motion, then our map becomes a sort of ‘Rosetta Stone’ for learning a new geophysical language. One in which the empirically true, and catastrophic, geological history of the western hemisphere is recorded in exhaustive, and intricate, detail.

Published in: Uncategorized on April 14, 2011 at 4:26 pm  Comments (2)  

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  1. I am really impressed!

    I hope you post a teaching lesson with examples of images at various scales and how to discern the melt flows.

    I wonder how thick the flows can be — this would show how great the gas blast pressures are.

    Do the supersonic winds blow melt spray off the top of the waves of melt, like waves on the beach?

    Have you seen intersecting waves at an angle that create interference patterns?

    The mountains on the southeast corner of Fresno, CA clearly show melt flow from the west that run up the west side of the mountains and overrun the top ridge.

    What are the temperature range of the melt flows?

    Have you seen lighter rocks carried along on the top of any flows?

    If we can find where the flows have covered thick trees, not too deep or hot, then we can get charcoal samples for accurate carbon dating, as the flow would keep out oxygen from the air, so the trees would bake into charcoal.

    Keep up your creative work!

  2. Thanks Rich,

    I’ll add a few photos, and illustrations, to this post over the next few days.

    The temperature of the melt in Mexico, and west Texas is yet to be determined . That’ll have to wait for field work.

    As for the stuff near my home here in Ca.: When you live at the foot of a mountain range that reaches up over 13,000 feet, anything that’s less than 1000 feet is just a foothill. So Campbell mountain barely makes the grade.

    But the burnt facies here are confusing to say the least. The heat signature is unmistakable as you walk among those rocks. And most of the larger, house sized, boulders have the kind of deep thermal fractures like you see in boulders of lava that have cooled very quickly in the open air after a eruption. But they do not consist of lava. And there has been no volcanic activity on the west side of the Sierra Nevada pluton since the early Mesozoic. Or more than 200 million years.

    Many of them almost seem to be hollow. (they ring like a bell) And, while internally, they have the color of white granite, the grain size of the crystals in the rocks is all wrong. They have a black coating, anywhere from 1/8” to as much as 2” thick. And that grades in texture from smooth, and glass-like to a foamy, texture like pumice. Whatever the the black coating is, it’s not desert varnish. And a fragment of the stuff will stick to a magnet as solidly as any meteorite.

    The thing is, the burnt facies here are so dramatically obvious to one standing on the ground among these rocks that until as late as 1966, they were still teaching in the local high schools that Campbell mountain is an ancient volcanic plug. Yet, today we know that’s not true, under the SEM, there is no clear evidence of melting.

    I’ll still waiting for detailed chemical analysis . I’ll be updated everything when those results come in.

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