(Visited 61 times, 1 visits today)FacebookTwitterPinterestSave分享0 One Colorado storm in 2013 caused hundreds or thousands of years’ worth of mountain erosion. This is causing a rethink on the power of catastrophic events.A big storm hit Colorado in September 2013. Scott, Suzanne and Robert Anderson of the University of Colorado went looking for geological changes that resulted to the Front Range of the Rockies. In the journal Geology, they report 1100 landslides and debris flows in a “historically sedate landscape.”Comparing our results against published long-term erosion rates, we find that these mass movements evacuated the equivalent of hundreds to thousands of years of hillslope weathering products. We conclude that (1) rare debris flows perform the majority of sediment transport and channel erosion within steep channels along the eastern edge of the Front Range, potentially explaining discrepancies between modern sediment yields and long-term erosion rates in such settings, and (2) the high spatial density of debris flows along the corridors bounding steep canyons suggests that the landscape switches to debris-flow dominance as knickpoints pass headward along the canyons.As dramatic as this one storm was, its impact on geological thinking may be more monumental. Recounting centuries-old debates about the rate of geological change, Scott McCoy of the University of Nevada in Reno comments on the paper in the same issue of Geology:How do surface processes shape the landscapes in which we live? Is it the every-day flow of rivers that gently, yet persistently, erodes and transports sediment from highlands to ocean basins, dissecting the land surface into networks of ridges and valleys? Or is it cataclysmic events of incredible magnitude that, despite their infrequency, conspire to shape Earth’s surface? These questions highlight the debate over the relative importance of extreme events in sculpting Earth’s surface, and are as old as the science of geology. Although geologists have gathered data and proposed theories supporting both Hutton’s (1795) and Lyell’s (1830) uniformitarianism and Cuvier’s (1818) catastrophism for over 200 years, the paper by Anderson et al. (2015, p. 391 in this issue of Geology) shows that the debate is still active and that, even with new tools, we have much to learn about the degree to which observations of modern sediment transport processes quantify the full range of formative geomorphic events.If infrequent storms like the one in 2013 dominate the mass movements in geology, then “historic records of sediment flux that have not captured an extreme event might grossly underestimate the actual long-term sediment flux.” We must keep in mind that formal historical records only go back a little more than a century in America. Before the west was settled, and geological pioneers like John Wesley Powell came after the Civil War to study the canyons of the Colorado Plateau, there would have been only Indian legends and word-of-mouth records by scattered populations of settlers. Events of this magnitude in Colorado could have been completely unobserved by settlers in Arizona or Oregon, and vice versa. The problem continues to this day; McCoy says that the Andersons used tools and models that didn’t exist just 20 years ago.McCoy realizes that the consequences of underestimating actual erosion rates are huge:Misunderstanding such a discrepancy between modern and long-term erosion rates can lead to inaccuracies in: predicting the life span of reservoirs; determining the impact of changing land use; setting attainable water-quality standards; and mitigating sediment-related hazards, such as rapid mass movements like landslides or debris flows, and extreme river channel aggradation. At longer time scales, accurate portrayal of the magnitudes and spatial-temporal patterns of sediment fluxes is critical for understanding how landscapes evolve, how sediment fluxes might change with a changing climate, and what flux of sediment and nutrients is required to maintain healthy ecosystems.Nothing can replace actually being present to measure what happens in an extreme event. Based on their empirical observations Anderson et al. conclude that debris flows account for the majority of geomorphic work along steep mountain slopes. But “there is no agreed-upon mechanistic framework to describe the controls of bedrock incision by debris flows,” McCoy says, “unlike rivers, which in turn raises questions about the accuracy of predictions regarding the pace and spatial pattern of steep land evolution from models that do not consider the effects of episodic debris flows.”McCoy ends on an optimistic note, basically saying that geologists’ models and tools are getting better. It’s clear, though, that he was surprised himself: “The intriguing result is that, in a single event, debris flows transported hundreds to thousands of years worth of accumulated hillslope material into the main stem rivers.”Update 5/20/15: With the lessons of 2013 fresh in memory, a press release from the Cooperative Institute for Research in Environmental Studies warns that Colorado’s biggest storms can happen any time. Average rates of precipitation are unreliable, the article says, because “they’re based on observations of events that don’t happen frequently and because the observations themselves are limited, especially in remote areas.”This is another case of how scientists can go astray by assuming the unknown. How many decades—indeed, centuries—have the experts and their textbooks been teaching “inaccuracies” about the pace of geomorphic change? “We have much to learn,” McCoy says. Well, most textbooks and TV documentaries don’t say that. They teach slow-and-gradual evolution of the earth as fact. Remember, it was Charlie Lyell’s gradualism that inspired Charlie Darwin to dream about the long, slow accumulation of gradual change in life as well as geology.It doesn’t take long ages to produce rapid change, if the cause is sufficiently energetic. Now, this one storm just two years ago has been shown to produce hundreds or thousands of years’ worth of geological change. Scratch that; how do they even know those estimates? Nobody was watching the Colorado Front Range thousands of years ago. For all they know, this one storm did millions of years’ worth of change. After all, when you’re dealing with unobserved fantasies, numbers don’t really matter, as long as they support the time Charlie D. needs. And did you notice that the climate change alarmists rely on models that have used bad data about geomorphic change rates? e.g., models inform “how sediment fluxes might change with a changing climate….”One would hope that this embarrassing discovery would give the secular geologists a little humility, so that they might take alternatives more seriously. After all, PhD creation geologists have been demonstrating evidence for catastrophism for years. Dr. Steven Austin compiled a database of published papers documenting rapid, massive changes. Dr. Andrew Snelling’s two-volume work Earth’s Catastrophic Past describes many documented events, as well as massive formations that could not have formed gradually. (This is a new work in the heritage of The Genesis Flood by Morris and Whitcomb in 1962 that launched the modern creation movement.) The peer reviewed Quarterly of the Creation Research Society, published continually for 50 years now, regularly publishes accounts of geological phenomena that demonstrate catastrophic change. One would hope, but don’t hold your breath. The gradualists will just look at this Anderson paper and say, “Well, that’s interesting” and continue on comfortably inside their falsified paradigm. Gradualism works. It works in the imaginations of uniformitarian moyboys unconstrained by empirical data, dogmatically committed to an old earth.
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