We believe that the Andes Mountains are 25 -30 million years old, or at least that is their start date, based on a variety of dating techniques. They took a long time to rise. But for a while, they were believed to be much younger, perhaps 7-8 million years old. The younger date is interesting because it provides a study in how easy it is to draw a mistaken conclusion from data that are good, but don’t quite cover all the bases.
The younger year date was based on the steep rise in the near-pure 16O in the sediments east of the Andes or in lake-bottom sediments in the area. Since such sediments come from the mountains, they represent chemical processes on the mountaintops; and since the proportion of 16O remaining in a cloud is greater the higher the cloud rises before dropping all its rain, the sudden increase in 16O sediments seemed to suggest a sudden rise in the mountains, — 4,000 feet in 4 million years.
This was not an unreasonable inference, though it was an awfully fast uplift.
However, in due time, someone pointed out that a simple increase in rainfall will pull the 18O out of a cloud leaving a higher proportion of 16O, and thus an increase in rainfall can change the isotopes available on the mountaintop just the same way as an increase in height. Was there an increase in rainfall during the rise of the Andes?
There was, and they did not spurt up in 4 million years, but took perhaps four times that long. All this just to say that there’s always a new twist, always something new to learn, always an unexpected turn of events in the sciences. You really want several converging lines of argument, not just one, no matter how carefully researched.
On the other hand, none of these events could have prepared anyone for the image of our Lady in the rocks of Las Lajas, at the back of a cave near Ipiales Columbia. And this brings me to an entirely different topic, a topic that is not specially related to any particular science, but to the philosophy of science. It is a topic that I would like to explore with this minor discussion of the Andes Mountains, the miraculous image they house, and the possibility of scientific error and correction all in the background.
What is a miracle?
How can it be defined?