If you follow the latest science news, whether it’s a newsfeed from Science Daily or a casual listen to Ira Flatow on Friday afternoons, you may have learned that Earth, indeed, has a pulse. As reported in the journal Geoscience Frontiers, rigorous statistical analysis for the timing of 89 major geological events of the past 260 million years revealed clusters of events occurring nearly simultaneously at intervals of 27.5 million years. These ten event-clusters involved geological upheavals and global environmental crises such as extensive flood basalt eruptions, shifts in the Earth’s tectonic plates and sea levels, deep ocean anoxia, and animal mass extinctions.
While the reporting makes it sound like a stunning, novel revelation, the authors of the paper point out from the first sentence, “There is a long history regarding the questions of temporal coordination among various geological events.” They cite previous articles dating back to 1924 that feature such preeminent geoscientists as Amedeus Grabau (1870-1946) and Arthur Holmes (1890-1965). The authors could have followed the paper trail back even further to the catastrophists of the early nineteenth century, who believed that gaps in the geologic column and fossil extinction patterns revealed dramatic “revolutions” in Earth’s history. Those original catastrophists, including French paleontologist Georges Cuvier (1789-1832), lacked the modern dating technology to quantify the durations of geologic time between the perceived revolutions. As I happened to mention in my March CSR blog, Britisher Holmes pioneered radiometric dating in 1911. But, more recent improvements in dating precision were necessary for the kind of statistical analysis reported in the Geoscience Frontiers paper.
Senior author Michael Rampino has been working on this problem for a number of years, too. Rampino is a geology professor in the Department of Biology and Environmental Science at New York University, and he just might consider himself to be a modern-day catastrophist or, better, neocatastrophist. However, his is not to be confused with the sensational catastrophism of Immanuel Velikovsky (1895-1979) or young earth creationists such as promoted by Answers in Genesis, both discounted by the scientific community at large. The scores of papers Rampino has authored related to the topic and the 9000 plus citations documented by Google Scholar locate him well within the scientific mainstream. He has individual papers that gained nearly as many citations as all of my papers combined! The provocative concluding sentence of the paper does, however, hint at rebellion, “Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists.”
Center for Data Science, New York University), applied spectral analyses (Fourier transform) to the precisely dated events to reveal a strong period signal of 27.5 million years and a secondary signal with a period of 8.9 million years. Scientists have previously reported 26-to-36-million-year cycles for various geological, environmental and biological events. The earliest work that I recall was by David Raup and Jack Sepkowski, who applied statistics to Jack’s remarkable data set of fossil ranges (first and last appearances in the fossil record) and detected a 26-million-year periodicity to 12 major extinction events over the past 250 million years. They noted that two of the events in their data set correlated with known major impact events (end-Cretaceous and Eocene). The present contribution links clusters of events with a 27.5-million-year periodicity. Future work will undoubtedly seek a similar trend back even further in Earth’s history.
What would cause such recurring coincidence of bad luck for planet Earth? David Raup suggested that the sun and a rogue companion star (Nemesis, of course) interacted in a 26-million-year cycle that pulled comets and asteroids toward the inner solar system. Nemesis remains undiscovered and probably doesn’t really exist. Rampino doesn’t know the cause either, but he anticipates that it involves some kind of deep Earth dynamics related to global tectonics and climate change…. or something closer to Raup’s imagination. Rampino notes that the solar system moves through the mid-plane of our galaxy with a vertical oscillation of about 32±3 million years. Enhanced cosmic radiation in the galactic plane may trigger climate change (let alone genetic mutations, which he does not mention). Concentrations of dark matter in the plane could interact with earth materials to produce heat, resulting in an uptick in geologic activity such as tectonic movement and global volcanism. Dark matter might also trigger comet showers from the Oort Cloud of the distant reaches of the solar system. But I wonder what happens if dark matter interacts with living biological tissue! Not to worry. Since the most recent cluster occurred about 7 million years ago, there are another 20 million years before someone finds out.
I have some thoughts and predictions of my own regarding this story. Perhaps New Age devotees will hail the 27.5-million-year pulse as a manifestation of Gaia, the goddess planet they worship as the mother of all life. Perhaps a Christian apologist, in earnest, will find a Bible verse corresponding with such a natural cycle, seemingly proving the scientific veracity of scripture. And how might a young earth creationist respond? The pattern in YEC has been to accept the basic chronology of events as they unfolded in natural history, but to compress them to their abbreviated, 6000-year-universe time frame. This is demonstrated in the acceptance of many geological concepts developed by mainstream geoscience, such as continental drift maps (embracing the evidence for supercontinents Rodina and Pangaea), the basic order in the fossil record (attributing it not to evolution and time, but to ecological zonation) and the history of global sea level change (as revealed by the distribution of marine sedimentary rocks on continental shelves and interiors).
An exhibit at the Creation Museum claims that geologic activity in the Earth (earthquakes and volcanism) has declined logarithmically since the creation week and the flood. A chart, created by a prominent flood geologist, shows the declining volume of volcanic ash ejected from a string of past eruptions. When I visited the museum, I observed that the graph omits a number of volcanic eruptions that, if included, would completely contradict the claim made in the exhibit! No such regular and dramatic decline is supported by the geologic record. Since the data in this study documents regular cyclicity in geological activity with statistical precision, how will the YEC community respond to it? Certainly, they will question the validity of the radiometric dating, but here they are also in a bind. The same logic of logarithmic decline is applied to the concept of radioactive decay. The geologic record in this study extends halfway back into the record of the flood by their own interpretation of global stratigraphy. If, indeed, radioactive decay was faster during the creation week and flood, as proposed, the cycles should either not cluster at all or the intervals between clusters should progressively increase over the time span of the dataset.
The paper by Rampino, Caldeira, and Zhu provides a great example of how scientific ideas advance from reasonable, but unproven hypotheses (re: Holmes, Grabau, Raup) to more robust datasets and testable theoretical explanations. There is a good chance that further studies will validate the evidence and constrain the periodicities for these kinds of Earth cycles, whether or not pulse is the most appropriate label for them. The jury is out on internal or extraterrestrial triggers. There surely are exciting opportunities for future studies ranging from geo- to astrophysics. The jury is also out on how the study will be interpreted or appropriated in popular culture or in typical intersections of faith and science.