Previous posts in the series:
- On the Grand Canyon and the Flood (1)
- On the Grand Canyon and the Flood (2)
- On the Grand Canyon and the Flood (3)
- On the Grand Canyon and the Flood (4)
- On the Grand Canyon and the Flood (5)
- On the Grand Canyon and the Flood (6)
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The Grand Canyon, Monument to an Ancient Earth: Can Noah’s Flood Explain the Grand Canyon?
By Gregg Davidson, Joel Duff, David Elliott, Tim Helble, Carol Hill, Stephen Moshier, Wayne Ranney, Ralph Stearley, Bryan Tapp, Roger Wiens, and Ken Wolgemuth.
We now come to Part 4 of the book; the carving of the Canyon. Chapter 16 is an assessment of the most common flood geology arguments for rapid carving of the canyon. Chapter 17 covers the conventional geologic understanding of how the canyon was carved. Chapter 18 focuses on what we can tell about the canyon’s history since the time of the carving.
Chapter 16 — Carving of the Grand Canyon: A Lot of Time and a Little Water, A Lot of Water and a Little Time (or Something Else) deals with the false dichotomy of the flood geologists. Was it a lot of time and a little water or a lot of water and a little time as if these were the only two options? As it is shown later in the chapter, an important third option is left out.
Perhaps the most intriguing question regarding carving the Grand Canyon is how the Colorado River managed to cut a channel through the Kaibab Arch.
The crust at this location bows upward creating an arch that rises 3,000’ above the land on either side. How did a canyon form that allowed the Colorado River to flow though it instead of around it. Flood geologist posit that large lakes were impounded behind the arch (when it was uplifted) with water left over from the flood as shown on Figure 16-1 from the book. They say the lakes contained over 3,000 cubic miles of water; 3 times the amount of Lake Michigan. At some point after the flood the dam burst and the water spilled carving the canyon in a matter of days. Now, to be fair, non-flood geologists have proposed a “spillover” model (although at a much smaller scale) that was presented in the symposium on the Origin of the Colorado River in 2000. The ancient lake in question is Hopi Lake on the figure above also referred to as Lake Bidahochi located in the region where the Little Colorado exists today. Of course, flood geologists immediately seized upon it as confirming their breached-dam hypothesis. Although seriously considered for a time, most conventional geologist now reject it as the bulk of the evidence does not support it. The problem with the breached-dam hypothesis is that extensive large-scale lakes leave readily identifiable evidence by the characteristic deposits that form when sediment carried by rivers flow into a large lake, slows, and deposits. There is a lack of evidence that these lakes were extensive as claimed, or that some of them even existed at all. Recent studies of the Bidahochi sediments show that the lake pictured as Hopi Lake by flood geologists was not one big lake at all, rather a series of playas (lakes that seasonally dry up) that were never able to spillover or breach a dam. In fact, evidence for a spillover or failure point for this proposed lake has yet to be found.
Figure 16-4 from the book illustrates what we should expect to see for a raging flood in soft sediment versus a multiple cycles of seasonal floodwaters gradually incising through layers of hard rock. In the first scenario sand and lime will wash away much more easily than clay, so the massive burst of water should leave clay layers sticking out. As the water recedes the weight of the overlying layers will cause the clay and lime to extrude like putty in the channel, resulting in thinning and sloping downward near the edge. Finally slumping should leave piles of mixed sediments at the base of the exposed embankments. In the second scenario, rivers should carve downward into the already hardened rock, leaving vertical walls behind. Erosion of the weaker rock layers during seasonal flooding should undermine the cliff faces (step 2b) and result in collapse and widening of the canyon (step 3b). The layers should not thin or slope downward near the cliff edges because the layers are solid rock. Shale, being much softer than sandstone or limestone, erodes faster resulting in the collapse of overlying harder layers and producing an ever widening canyon with shale benches and sandstone and limestone cliffs (step 4b). Debris from the higher layers will be common on the benches but less common at river level, where seasonal floods wash it away.
So what is observed? None of the expected features for the flood geology model are observed. All the expected features from the conventional geology model are observed. Furthermore, even if the dam water could cut through 4,000 feet of soft sediment layers left by Noah’s flood, by that time most if it would have drained out of the Grand Canyon area and the remaining water would not have enough erosive force to cut through another 1,000 feet of very hard metamorphic and igneous basement rock to form the Grand Canyon’s Inner Gorge.
Fortunately, we do have an example of where a megaflood carved a landscape. We have already talked about Lake Missoula, the glacial ice-dammed lake that spilled out catastrophically over Washington and Oregon. Lake Missoula may have contained 500 cubic miles of water that abruptly emptied – likely several times as the ice formed, breached, and re-formed. This megaflood created the Channeled Scablands of eastern Washington, a vast landscape of erosional features overlain on lava rock. Figures 16-6 and 16-7 from the book show aerial views of the scablands.
So what does a megaflood do when it spills out? It doesn’t create a grand canyon, it creates multiple wide, shallow channels, which fan out over a large area- not a deep, narrow single channel. Additionally, note the total absence of any sharp bends or meander loops in the eroded channels. Megafloods spill over the top of tightly bending channels, carving a new channel that cuts off the bend. Go to the beach (I really want to go), take a stick and cut a meandering line in the wet sand. Take a 5 gallon bucket and throw the water at the line. Did the water follow the line and deepen it, or did it wash over it creating something that looks like the figure above. The landscape of the Channeled Scablands is a compelling argument against a megaflood origin for the Grand Canyon.
When Mount St. Helens erupted on May 18, 1980, nearly a cubic mile of hot pumice rock and ash slid off the north face of the mountain and filled the valley below. 22 months later a small eruption melted the deep snow in the mountains new crater and sent a large flash flood of water and mud rushing into the North Fork Toutle River Valley. This flash flood immediately began cutting a new network of channels in the loose ash. These rapidly forming canyons are offered as evidence supporting rapid formation of the Grand Canyon by flood geologists, but little attention is given to anything other than how fast they formed. The numerous U-shaped small canyons cutting into the ash do not look anything like the single, massive, V-shaped Grand Canyon. As vertical walls formed in the soft ash, the unsupported ash slumped and dropped piles of loose material down into the stream channels. In great contrast, the Grand Canyon walls remain vertical at heights of hundreds of feet, with no evidence of slumping and no piles of un-cemented sediment at the base of the cliffs. The striking difference between Mount St. Helens and the Grand Canyon provide strong evidence the Grand Canyon layers were rock when they were carved, not soft deposits like Mount St. Helens.
So was the Grand Canyon carved in a lot of time by a little water, or by a lot of water in a little time? But as the book said; that is a misleading question. If you do the math assuming the average annual precipitation that falls on the drainage area now (and bear in mind there may have been more rain during wetter periods in the past), we would estimate that 61 million cubic miles of water has been eroding the Grand Canyon during the last 6 million years. That is a lot of water and a lot of time!
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Photo by ccho at Flickr. Creative Commons License