During the nineteenth century, many a traveler throughout America’s heartland found themselves transfixed by their observations of large, errant boulders which occasionally sprang from the landscape in the middle of large stretches of forest or fields. These mysterious stony outcrops appeared to defy the expectations of geologists, since they were not associated with any native veins of similar stone. The question at the time had been, if not of natural geologic origin, what was the origin of these massive stones?
Known today as erratics, a word derived from the Latin word meaning “to wander,” these massive stones are believed to have been transported by the movement of glacial ice during the Pleistocene. However, to nineteenth-century travelers, the mysterious misplacement of these massive stones had presented serious problems and aroused a number of creative theories about their origins.
One leading theory among investigators at the time had been the notion that erratics represented evidence of the great flood described in the Christian bible, or at very least, some similar flooding event that occurred sometime after Earth emerged from the most recent ice age. According to this view, the colossal energy of floodwaters would have provided the necessary force to have moved the stones. However, by the middle of the nineteenth-century research by those like Swiss naturalist Ignaz Venetz began to focus on how glaciers offered a better explanatory mechanism for the mysterious erratics.
Following Venetz, the publication of Charles Lyell’s Principles of Geology also offered an explanation for the curious movement of erratics with the aid of glaciers. Similar observations had been made by the German polymath Johann Wolfgang von Goethe and several colleagues that stones found along the slopes of the Jura Mountains had likely been deposited after the movement of glaciers during the last ice age. Even naturalist Charles Darwin, best known for his contributions to the theory of evolution, had taken interest in these geological wonders of the ancient world and wrote of his observations of erratics from aboard the HMS Beagle while sailing south of the Strait of Magellan.
Of course, while glacial movement appeared to be a reliable mechanism for the movement of such massive stones, the question remained as to what might have placed them on top of glaciers to begin with. The leading theory about this among nineteenth-century scholars had been that landslides and rockfalls, occasionally helped along by the movement of the encroaching ice itself, had likely resulted in stones coming to rest upon the ice sheets, which were thereafter carried along as the glaciers moved. Once the ice sheets began to melt and the glaciers receded again, these stones—some of them carried along for great distances—would have found their way to their present positions on the ground far from where they originated.
While such geological mechanisms are well understood today, there are still some erratics that maintain a few unusual aspects. Along the coasts of Washington and Oregon today, several erratics can be found which appear to have spent a significant amount of time below ground. Mostly of basaltic origin, these peculiar stones are otherwise similar to other known glacial erratics, although the evidence suggesting that they have spent significant amounts of time as much as 40 kilometers below Earth’s surface seems to preclude their movement above Pleistocene glaciers. So where did they come from, and how were they moved to their current positions?
Geologists have noted that these unusual erratics are in an area where few fossil discoveries have turned up. Some have gone so far as to suggest that there is evidence of some kind of disruption or another mechanism that causes this part of the northwestern coast to appear “upside down,” at least geologically speaking.
In 1980, researcher Robert Muir Wood offered a theory about the origins of these curiosities in his New Scientist article "Orphans of the Wild West.” The theory proposed for the region’s odd appearance and its potentially non-glacial erratics suggests that these stones were forced down to great depths in the ancient past, and later carried back to the surface by geological pressure that squeezed the surrounding soil, causing them to rise again to their present aboveground positions.
While the theory appears to make sense, not everyone saw it as the most viable explanation for the curious non-glacial erratics that appear to have been left “orphaned” along the coasts of certain western states. While the debate over their origins remains, the question over what mechanism might have actually led to these seemingly "non-glacial" erratics is, of course, a fascinating one.
Hence, perhaps at least a few of these mysteries of the geological past remain unexplained today, and no less perplexing to the modern scientists who continue to marvel over them.