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.