Raising a Titanic Geological Plateau
The Colorado Plateau is a huge region covering parts of four states. It’s over a mile higher than its surroundings, but its layers are remarkably flat. How did this region, littered with marine fossils, rise into the sky? Three American scientists writing in Nature last week believe they have a mechanism:1 it heated from underneath and rose like a cake.
Explaining a vast heterogeneous region like the Colorado Plateau is tricky. The plateau includes the Grand Canyon and the other amazing landforms of the Four Corners Region – Bryce Canyon, Zion, Canyonlands, Arches, Capitol Reef, Grand Staircase, Lake Powell, Petrified Forest, Dinosaur, and numerous other local parks. There are mountain ranges, sediment layers miles deep, meandering river gorges, faults, volcanoes and areas where strata have been tilted 90° laterally for many miles. Moreover, this plateau sits within the middle of a tectonic plate. It’s not at the margins where most of the dramatic geological changes on earth takes place.
“The forces that drove rock uplift of the low-relief, high-elevation, tectonically stable Colorado Plateau are the subject of long-standing debate,” they acknowledged. This vast area in Utah, Colorado, New Mexico and Arizona “experienced ~2 km of rock uplift without significant internal deformation.” That fact is clearly evident at the lookouts of the Grand Canyon. Geological layers extend as flat as a pancake as far as the eye can see. It takes a lot of delicately-balanced force to lift up a region this large without deforming it. Imagine how you would you try to pick up a Guinness World Record layer cake the size of a city block and keep it from breaking.2
To try to get a grip on complex systems, scientists employ models. These allow them to focus on certain aspects they deem important without getting bogged down in details. The danger is that different scientists may disagree on the salient features needing to be explained. In addition, uncooperative details cannot be ignored; they might falsify the model.
Roy, Jordan and Pederson began by pointing out flaws in previous models. Note: the “Laramide orogeny” is a mountain-building episode that supposedly built the Rockies and other mountain ranges from Alaska to Mexico. It is presumed to have occurred in the mid-Cenozoic between 80 and 35 million years ago. Isostasy refers to the floating of crust on mantle; epeirogeny means large-scale crustal deformation. The Basin and Range province includes the parallel mountain ranges and valleys of Nevada to the west. The Cenozoic era follows the Cretaceous and is typically dated 65 million years ago to the present.
Previous ideas for Colorado Plateau rock and/or surface uplift fall into four categories: early- to mid-Cenozoic Laramide-orogeny-related shortening; mid- to late-Cenozoic epeirogeny; stream incision, and isostatic responses; and dynamic uplift. Here we show that even if the contributions from minor Laramide deformation and flexural isostatic responses to extension at the plateau margins and to net Cenozoic erosion are removed, there is >1.6 km of residual rock uplift that must be explained by post-Laramide tectonic processes. Dynamic uplift mechanisms can drive only 400�500 m of this residual amount, leaving approx 1.2 km of unexplained rock uplift.
Then they introduced their model:
We propose thermal perturbation and re-equilibration as a general mechanism for driving rock uplift within plate interiors, particularly in regions of thicker, more depleted lithosphere adjacent to zones of extension, such as the Colorado Plateau. Our model differs from previous ideas of thermal modification of the Colorado Plateau in that it relies on a post-Laramide process that is triggered by the removal of the Farallon slab and the onset of thinning in the Basin and Range and Rio Grande rift provinces. We show that thermal perturbation following mid-Tertiary removal of the Farallon slab can account for the majority of the observed rock uplift of the Colorado Plateau and, additionally, that this mechanism explains the observed rates of encroachment of the onset of Cenozoic magmatism onto the plateau.
The bulk of their paper explained the details of their model. It is important to realize that no model of a historical episode can be proven, or even adequately tested. At best, scientists can try to find data consistent with it, and see if the overall scenario explains the bulk properties of the system. A good model should also make predictions.3 These scientists felt that by having a slab of rock slide away under the plateau, leading to increased heating from the mantle, they could explain the 2 km rise. A model is never the final answer, however. “Future, more detailed, comparisons with phase relationships in a melting model must incorporate variable chemistry and hydration of source regions and changes in both chemical and thermal buoyancy during and following the mid-Tertiary ignimbrite flare-up,” they said. They did not return to the observation that the layers are flat and largely undeformed.
1. Roy, Jordan and Pederson, “Colorado Plateau magmatism and uplift by warming of heterogeneous lithosphere,” Nature 459, 978-982 (18 June 2009) | doi:10.1038/nature08052.
2. Note also that this is just the latest uplift. Geologists believe this vast area rose and sank several times without significant deformation. In the Grand Canyon, for instance, the Hermit formation (marine) is very flat along the Bright Angel Trail. But the Coconino Sandstone, supposedly consisting of petrified sand dunes from a desert, sits just as flat on top of it. Above those, the Kaibab and Toroweap limestones sit as testaments to another undersea episode. Thousands of feet of more layers from alternating wet and dry periods are above those. It stretches credulity to think that these layers bobbed up and down repeatedly without deforming.
3. The fallacy of “affirming the consequent” renders many predictions dubious: “p predicts q; q occurs; therefore p caused q.” Just because a prediction is confirmed, it does not guarantee that no other model could account for it. In fact, there could be an infinite number of other theories that could account for the phenomenon. This is what caused Karl Popper to jettison prediction as a criterion of science and propose falsification instead (but falsification only lasted a couple of decades before other philosophers discounted its value in science).
One of the things CEH wishes to educate its readers on is how to be a good skeptic. Laypeople tend to exalt anything published in a scientific paper as something to honor just because it is found in a scientific journal. You wouldn’t give a politician unqualified honor, so don’t give it to a scientist. He needs to prove his case. Learn to be bold. Examine, test, reason, and question. Even if you don’t understand all the jargon, you can learn to discern baloney and flawed reasoning.
Skeptics will find many reasons to doubt this model. For one, it is married to the geologic column and evolutionary timescale. This forced them to tie phenomena to an artificial system rather than let the data speak for themselves. They could not dare to stray outside the paradigm. Getting something to fit within a paradigm, however, is not the same thing as explaining it in the real world.
Another problem is that they employed question-begging terms masquerading as scientific explanations. For instance, look at the term orogeny (mountain-creating). What made the Rocky Mountains? Answer: the Laramide Orogeny. This is equivalent to answering a child’s question about why a ball falls by saying “because of gravity.” What’s gravity?, the child asks. Answer: A force that makes balls fall. Should the kid be satisfied to learn that the ball falls because it falls, or mountains form because mountain-building forces formed them? But that is how a previous model explained it: the plateau lifted up dynamically because of “dynamic uplift.” Even a kid would know that’s a dodge. Giving it a proper name like Laramide doesn’t help. Example: What ancient people built this cliff dwelling? Answer: the Anasazi. Well, since the word Anasazi means “ancient ones,” the answer provides no information, even though it sounds sophisticated.
Another cause for skepticism is the ad hoc nature of the model. The scientists imagined a plate slipping under the middle of another plate, that caused heating, and then the whole region rose 2 kilometers. How convenient. Have they really explained it, or did they just make up a story to get their model to work? Another ad hoc speculation not mentioned in this paper but stated in many Grand Canyon guidebooks is that huge time periods are missing between the layers. The entire Ordovician and Silurian systems are not found in Grand Canyon, for example. You can take one step on the Bright Angel Trail between conformable layers and they will tell you that you just stepped across 100 million years of “missing” geological time. What? The explanation does not rely on empirical evidence, but on the absence of evidence! There are several places where strata are missing. Almost a billion years is missing between the Great Unconformity and the overlying Tapeats Sandstone. No evidence for the erosion that would be expected over such vast periods of time can be found.
Perhaps the biggest cause for skepticism, though, is the ignoring of important details of the Colorado Plateau that would falsify the theory (see Glittering Generalities). Their model explained nothing about the lack of deformation. How could these layers be lifted up 2 kilometers without buckling? Many strata in the Grand Canyon cover hundreds of square miles – some of them, indeed, extend across much of North America. This is comparable to a sheet of paper several miles in extent being lifted up without tearing or tilting. Explaining how these layers could rise and fall over and over without deforming is arguably more important than explaining how they rose at all. Isn’t that the question they should be asking? In addition, the lack of erosion between many of the layers should falsify the belief that they were laid down over millions of years. And the fact that faults and folds extend through all the layers, but don’t stop halfway up, makes the hypothesis of vast time periods implausible. Numerous other evidences indicate that the strata in the Colorado Plateau must have been laid down rapidly and catastrophically, but these were all completely ignored in their effort to present a model that comports with the secular evolutionary paradigm, only because Charlie & Charlie (Darwin and Lyell) needed lots of time for their slow, gradual processes to build scientists out of slime.
When reading details of a scientific paper, don’t lose sight of the belief system that generates the explanation. This explanation was restricted to the secular evolutionary paradigm. It has no necessary correlation, therefore, to the true history of the world. Moreover, it did not honestly deal with the alternatives and with many falsifying details. It ignored voices of anyone outside the paradigm. Jargon or not, math or not, such self-fulfilling, paradigm-preserving projects should not be honored with the noble name of science.