The worlds largest rock tumbler?
This story caught my eye this morning. GSA press release – The Strange Rubbing Boulders of the Atacama. It seems that every other day I read about some place on earth that has a strange story to tell and usually that story is difficult to understand without an earth that is of great age. Here we have a high mountain valley in one of the driest places in the world, the Atacama Desert in Chile. In this desert valley are scores of huge boulders that apparently have broken off from the mountains around and made their way to the dry valley below but they are strangely girdled by a rounded erosion pattern that is not found on the tops of the boulders. How could thousands of boulders be sitting on top of a flat valley where there is no evidence that there has ever been standing or significant water erosion have come to have these rounded sides? How could some of the boulders have traveled so far out into the flat valley away from their source?
From the press release: “The whole story appears to be that the boulders tumbled down from the hills above — probably dislodged by earthquakes. They accumulated on the sand flat, with no place else to go. Quade compares the situation to a train station where people are crowded together closely, rubbing shoulders as they waiting for a train. In this case the boulders have been stuck at the station for hundreds of millennia and the train never comes. So they just get more crowded and rub shoulders more over time.
Analyses of the boulder top surfaces suggest that they have been there one to two million years. That age, combined with the fact that seismic activity in the area generates a quake like that Quade witnessed on the average of once every four months, suggests that the average boulder has experienced 50,000 to 100,000 hours of bumping and grinding while waiting for that nonexistent train.”
So apparently this is a case of the one the worlds largest natural rock tumbler, albeit a rock tumbler working at slow speed over a long period of time. From the picture above you can see that some of these boulders are many yards away from the next closest boulder. It may takes hundreds or thousands of years for them to move by vibration over to another rock and come into contact it much less have enough contact to produce appreciable erosion.
I am not sure how creation scientists would try to explain these boulders but I do know that flood geology models would require that the boulders have been formed by flood sediments that were then pushed up into mountains after a global flood and so the solidification into rock, fracturing and then falling of rocks into the valley would have taken place after the waters of the flood receded. I expect that there is no evidence of any water in this location during the past 4000 years however I think that they may try to use the earthquake explanation for these boulders as well. The physics of erosion tells us that it would take a lot of jostling/bumping to cause this much erosion so I expect that the explanation might be that some time after the flood this area experienced much higher rates of earthquakes and possibly larger ones such that there was nearly constant vibration of the ground for several hundred years followed by reduced earthquake activity to the point we see today. Here we have another example of assumptions about rates that makes the difference in the explanations. In this case the assumption of long term consistency of earthquake rates is not unreasonable while vastly different earthquake frequencies in the past is not obvious from any of the evidence (here or elsewhere). Only a belief that these rocks could not have existed prior to 4000 years ago because of a global flood would cause anyone suggest another solution to how these rocks came to appear as they do.
Naturalis Historia 