Geology

Looking for Noah in the Navajo:

An Exploration with a Geologist in Zion National Park

In May, 2014, I was hiking the Zion Canyon Overlook Trail with geologist Gerry Bryant. Zion National Park’s iconic cliffs of cross-bedded sandstone inspire wonder, of course. They also pose commanding questions. Where did all that sand come from? How did it end up here in southern Utah? What made it turn into stone? How did the canyons get cut into the rock? There were smaller curiosities to puzzle over as well: fossil sea shells, tracks of dinosaurs and other critters, petrified wood and worm burrows and fossil horsetails.

The first time I hiked the Zion Canyon Overlook Trail with Dr. Bryant, he did not have a Ph. D. and I was not a geologist. That was almost twenty years ago. Four families spent a weekend camping together in the park. Sabbath afternoon, at skinny places along the trail, dads shepherded little tykes. At the overlook, we were enthralled by the ineffable beauty. Light danced down the towering sandstone walls. Luminous clouds cut the deep blue overhead.

We talked about earth history, of course. How did these cliffs and this canyon get here? We were Adventists. The doctrine of our church asserts the cosmos (the heavens and the earth) was created in six days, 6000 years ago. In this telling of earth’s story, the geologic column (at least the part of it containing fossils) was formed during the 12 months of Noah’s flood about 4000 years ago. It’s a grand but implausible story. Sitting in that immense stone amphitheater, we puzzled over how to hold together piety, integrity, intellect, faith, Bible and science. We did not agree, but no worries. The conversation was fun.

Since that Sabbath afternoon in Zion, Gerry had completed his graduate work at the University of Toronto. He is now director of the Geology Field Institute at Dixie State University in St. George, Utah, and directs the work of graduate students from several universities in their research in the Navajo Sandstone. My own accumulation geological credentials is a bit more modest—a couple of college classes. In preparation for my time in the field with Dr. Bryant this past May, I read a couple of technical articles related to Gerry’s research. Then most importantly, I had bought an unfashionable sun hat.

One of the research sites Gerry was going to be supervising that summer included outcrops along the Zion Canyon Overlook Trail. On this trip, Gerry was revisiting the outcrop, double-checking and extending observations he had made previously. A family of tourists noticed us looking closely at the rock and stopped to ask questions. Gerry explained what they wanted to know. A few minutes later I overheard the dad tell someone else, “Those guys over there are geologists.” I was rather pleased with the promotion and very glad I had bought the right hat.

The trail climbed steeply up from the pavement for fifty yards or so then leveled out and traced its way along a ledge for a mile or so. This ledge was the top of natural feature, a distinct, dark red band of rock that contrasted in both color and texture with the sandstone all around us. Gerry explained this dark red rock was an interdune deposit.

Interdunes are the low spots, the troughs, between dunes. When sand dunes form in areas with a high water table, these areas between the dunes sometimes dip low enough that the surface becomes moist or even is covered with open water. This moisture traps blowing sand in neatly horizontal layers. These horizontal layers are distinct from the angled layers of the dunes themselves. If the “pond” is not quickly buried by advancing sand dunes, the water will begin evaporating and carbonate will precipitate adding to the distinctive nature of the deposit. Sooner or later the sand dunes will march across the interdune, burying it. Later, a couple of geologists (Remember I had the hat to prove it!) will come along and find the fossilized interdune perched high on a cliff wall in Zion.

This particular interdune was huge, covering at least a square kilometer. It was associated with a massive disturbance recorded in the sandstone immediately above the interdune deposit. This disturbance is an example of something geologists call “soft sediment deformation” which is Gerry’s specialty. Back before the sand had turned into stone, the area was shaken by an earthquake which triggered a landslide down the face of a huge dune. At least that was Dr. Bryant’s theory. Not all geologists were convinced. Hence the need for more research. Hence my opportunity to tag along and watch a geologist at work and sneak in a few questions about Noah and the Navajo.

The Navajo Sandstone covers a hundred thousand square miles of Utah and adjoining states. In places it is more than 2000 feet thick. Before it turned into stone, it was an immense erg (sea of dunes) similar to ergs in the present day Sahara. But there are critical differences between the ancient Navajo erg and the Sahara. The dunes of the Sahara migrate before the prevailing winds, sometimes burying whole towns and oases with their palm trees, wells and houses. The migration is so inexorable that when all efforts at halting a dune’s advance across a village have proven futile, the final action of the villagers is to open the windows and doors of their houses so the sand will fill them completely instead of crushing them. Then years or decades later, perhaps the dune will have continued its march and the village will reappear in the following trough. Then life can again find a place in the oasis in the interdune. (See Sahara Unveiled by William Langewiesche.) Despite all this movement, the dunes do not build higher and higher. The sand does not get deeper and deeper. The dunes move across the desert surface almost like waves across a sea.

In the great erg that became Zion National Park, however, dunes climbed on top of dunes. Dunes buried interdune deposits, then built new “ground levels” above the interdunes. The wind would cut the top off one set of dunes and built a new set on top the foundation of the old. Over time the sand accumulated to more than 2000 feet in the center of the erg. Where did all this sand come from? How did it get here?

There are two competing stories. Both start in the same place: Appalachia. Creationists and geologists agree the Appalachian Mountains used to be much taller, and that the rocks of those mountains is present as sand in Utah.

Geologists imagine rivers that poured out of the ancient Appalachian highlands and stretched west across the continent, creating a broad system of deltas where they reached sea level in the area of modern Wyoming and Utah. The rocks of the mountains fractured and eroded in ways we know from modern mountains—freezing and thawing, heating and cooling, rain and floods, snow and glaciers. Gravity moved talus down slope. Streams in flood moved rocks downstream, breaking and smoothing them in the process, creating sand. Finer material moved the farthest, fastest. Silt moving all the way out into the sea beyond the western mouth of the rivers, sand getting deposited on beaches and bars. The low country created by these river deltas resembled the low country surrounding the lower Mississippi River. The climate dried. Wind began blowing the sand, concentrating it in a continental basin, creating the vast sea of dunes that eventually turned into the Navajo Sandstone.

Creationists imagine the waters of Noah’s Flood as gargantuan tsunamis sweeping around the world. This churning mass of water swept over the Appalachians, the violence breaking the mountains, then breaking the pieces of mountains into smaller and smaller pieces all the way to sand size. Even water as turbulent as this Flood could not carry large rocks very far. The Flood swept west across the continent. When it arrived at Utah, it was still at last 300 feet deep and moving rapidly. It dropped its sand load in Utah and swept back and forth enough to shape the dunes which today form the Navajo Sandstone.

Two stories. How are we to figure out which is more plausible? The first question is the nature of the dunes themselves. How can we tell whether these piles of sand were worked by wind or by water? I asked Dr. Bryant.

In the 1970s there was a sharp debate among geologists about whether the dunes were eolian deposits (that is transported and shaped by wind) or sub-aqueous (transported and shaped under water). The geologist who proposed the underwater theory argued the Zion dunes were more like dunes that had been discovered in North Sea than dunes in the Sahara. It was an interesting idea, Dr. Bryant said, but did not survive the test of further research.

Reading scientific literature after I got home, I found that everyone—geologists and creationists—agreed the Zion dunes are not identical to either the Sahara dunes or the North Sea dunes. Instead of a simple choice between “just like the underwater dunes in the North Sea” and “just like the wind-blown dunes of the Sahara” geologists have to weigh the relative merit of a variety of evidences. Even the most obvious feature of the Zion sandstone, the cross bedding, refuses to neatly, unambiguously settle the question once and for all. The angles in Zion’s sandstone are much steeper than is found in sub-aqueous dunes. But the angles are not quite as steep as the angles on modern desert dunes. In the context of the Flood argument, the cross bed angles point toward wind deposition, but leave just a little wiggle room for the creationists.

This is common in the arguments over earth history. Ancient deposits are seldom exactly like modern deposits. Limestone, coal, shale, mudstone, sandstone, lava flows, ash deposits—all have features in common with modern deposits and all have distinctive elements for which there are no modern equivalents. The ancient world was different from our world. Which, when you stop to think about it, is not all that surprising whether you believe in hundreds of millions of years or single-digit thousands.

Perhaps the next most obvious features in the Navajo after the cross-bedding are the interdune deposits with their carbonate minerals. Even allowing for every imaginable difference between the ancient and modern environments, it is difficult to imagine a process that could put those minerals into the sandstone in the middle of Noah’s Flood. Carbonate is an evaporite. It forms when water rich in dissolved carbonate evaporates. How could there have been multiple dry periods of sufficient duration or intensity to form the carbonate lenses scattered throughout the 2000 feet of Navjo Sandstone if the sandstone itself was formed in the middle of a global flood? (One creationist insisted to me that carbonate is not necessarily an evaporite. It was a precipitate. And evaporation is just one mechanism for precipitating carbonate from solution. That is technically true and irrelevant. I am unaware of any model, however implausible, for “precipitating” the carbonate lenses in the Navajo Sandstone. The carbonate lenses look like evaporation deposits.)

Another feature of the Zion sandstone that points to a sub-areal (under air) depositional environment are cross ripple marks. They are everywhere in Zion—fossilized in the sandstone and sculpted by the wind across the modern sand dunes that have formed from sand eroded out of the sandstone. This kind of cross ripples is characteristic of wind-blown dunes. They do not form on sub-aqueous (under water) dunes.

Dr. Bryant finished his examination of the outcrop on the Zion Canyon Overlook Trail, and we hiked back to the trailhead for lunch. After eating, we hiked into the canyon on the other side of the road, still tracing outcrops of the interdune and the zone of soft sediment deformation immediately above it.

Dr. Bryant was up high on the side of the canyon looking closely at something relevant to the research project. I was hiking parallel to him lower on the slope, outside the study area. I was looking at some of those cross ripples I mentioned earlier when all of a sudden I felt the thrill of discovery. The ripples were disrupted by little divots. I was pretty sure I had seen something like this a couple of days earlier. At another site in the Navajo Sandstone, Dr. Bryant and I had met up with a Ph. D. student from Loma Linda University and Adventist scientists Leonard Brand, Art Chadwick and Kevin Nick. The site included dinosaur tracks. Some of the tracks were obvious, like seeing dog prints in mud. But Dr. Bryant showed me other places where instead of looking down on tracks we were looking at them from the side. The animal had made tracks. The tracks had been buried and lithified, then erosion had cut down through the rock exposing the tracks in cross section. The marks I was looking at here in Zion reminded me of what we had seen that day.

Dr. Bryant climbed down to check my find. He acted almost as excited as I felt. They were dino tracks. Yes, for sure. He thought they were “new,” that is he did not think they had been previously mapped by park paleontologists. It was a real discovery. Needless to say, I spent the rest of the day intently examining every wind ripple outcrop we came across.

When you go looking for Noah’s Flood in Zion, these tracks are a big problem. Even if you could persuade yourself that chaotic water flow could sort the sand out from the silt and gravel, even if water could create the cross ripples and the high angles of the crossbeds, even if you could conceive of some mechanism to precipitate the carbonate minerals from the Flood waters, you would still face the question of how the dinosaurs managed to get here during the Flood to run around and make tracks.

Both YECs and geologists agree that much of the sand in Zion came from the Appalachian Mountains. Conventional geology imagines a broad delta system fed by rivers stretching from the Appalachians west across the continent, something like the vast, flat deposits we witness today in the Mississippi Valley south of Memphis. The rivers feeding this delta would create broad beaches and bars of sand, sand that could then be worked and sifted and transported by wind into the dunes of Zion. Flood theorists imagine Noah’s Flood crashing over the Appalachians breaking rock into sediment and carrying sediment to Utah.

A flood that washed over the Appalachians and carried sand 2000 miles would be a pretty violent flood. A leading YEC, Steve Austin, who believes the Zion dunes were created by Noah’s Flood, writes that the dunes could have been put in place by the Flood if the water was at least 300 feet deep. Which runs into a quandary: You need deep water for the dunes. You need very shallow water for dinosaurs. It’s kind of hard to imagine dinosaurs diving down three hundred feet to walk around on submarine sand dunes. If the tracks were found at the very top of the sandstone maybe we could imagine that the Flood washed in the dunes, then receded so that dinosaurs could come from somewhere and run around on the dunes. But the tracks are all through Zion sandstone from bottom to top.

Another problem: A fast-moving, massive flood would have mixed all kinds of coarse material and fine material together. But the sand in the Navajo Sandstone is clean. It would be perfect for a sandbox for my granddaughter. It’s difficult to describe a model for Noah’s Flood that could crush Appalachian rock into sand, separate the sand from gravel and silt, transport it 2000 miles, and drop it cleanly in Utah.

By now I was running out of Noah theories, so I turned my attention back to the research project that brought Dr. Bryant to Zion and gave me the chance to hang with a real geologist—soft sediment deformation. We hiked back to the road and explored up another canyon, looking for the edge of the interdune and the limit of the deformation. We found curious zones of deformation that ran between undisturbed layers of cross-bedding, features that raised more questions for graduate students to investigate.

Like Noah’s Flood, soft sediment deformation involves the intersection of water and sand and catastrophe. There is evidence of water all through the Navajo Sandstone—dinosaur tracks and worm borrows don’t happen in bone-dry sand. Carbonates must be in solution before they can precipitate. There is also evidence for catastrophe—soft sediment deformation is prima facie evidence of catastrophe. Where did the water come from—monsoon rains? Ground water? What were the catastrophes that jiggled the sand and caused the deformations—earthquakes? (This is the standard theory.) Were some of these deformations caused by the ground-shaking thump of massive dinosaur feet? (One of the questions in Dr. Bryant’s research.) The Navajo Sandstone asks plenty of questions of the curious looker. But so far, Noah’s Flood does not seem to be the answer.