The Mystery of the Megaflood

A review of the NOVA TV program on the Glacial Lake Missoula flood, PBS Television, United States. This program aired the week of September 19, 2005.

Editor’s note: Learn more about glacial flooding and the origin of the Lake Missoula boulders by reading Frozen in Time, Catastrophic Melting.


Geologist J Harlen Bretz in 1923 was the first to propose a radical geologic theory-that huge geologic features in America’s Pacific Northwest were formed by catastrophic water flow. He named the Channeled Scablands, with its catastrophically water-carved coulees, dry waterfalls, potholes and huge erratic boulders. At that time, most scientists believed these geologic features were formed by gradual erosion and deposition following the notion of uniformitarianism, which ruled out sudden changes in the landscape by catastrophic events.

For most of 40 years, two things prevented the scientific community from accepting Bretz’s theory. First, his peers did not come to the Northwest to personally check Bretz’s findings. Second, a source for the required humongous water flow had not been identified. Actually, geologist Joseph Thomas Pardee, who was present at the meeting of geologists when Bretz proposed his theory, had discovered evidence in Montana for a monstrous lake dammed up by a lobe of the Ice Age glaciers. However, the strong attitude of his superiors not to rock the boat and his job security may have prevented him from making it known for almost 40 years.

This new NOVA TV program has lots of great film photography, and at times is too fast-moving. Excellent animation recreates the action of super-cooled water under pressure which undermined the ice dam, causing dam failure and the catastrophic release of 540 cubic miles of water (1,400 km3) in just days-creating the scablands and backwater sediments.

The big question: Was there one Glacial Lake Missoula flood or many Missoula floods?

I respectfully take issue with the program’s interpretation that the 39 backwater sediment layers in the Walla Walla River valley in Washington state are the result of 39 repeat Missoula floods. Important field research by another team of Northwest geologists and scientists that I work with supports just one Glacial Lake Missoula flood. There is a time problem for the uniformitarians (i.e., those who believe in a long age for the earth) in that 40 floods repeating every 40 years or so makes 1,600 years just for the peak of the ice age. So, the issue of the number of floods presents a flood/ice age model time challenge.

The case for many Lake Missoula floods

The following is quoted directly from the NOVA program:

Narrator: “It was assumed that these layers were formed by changes in the speed of one giant flood … known as pulses … But that was before he [Richard Waitt] discovered something odd: a white line within the sediments, a layer of Mount St. Helens ash about 15,000 years old. At first it was thought that the ash had fallen into the waters and settled down between these layers. But could a layer of ash really sink down through hundreds of feet of turbulent floodwaters to form this amazingly neat clear (horizontal) line?”

Richard Waitt: “This whole column would be full of mud and sand and silt. To have something settle through it and come out like this, it’s impossible.”

Narrator: “This suggested something completely new: that all these layers weren’t laid down in one flood.”

Richard Waitt: “It suggested that periodically during the accumulation of this sediment that there had to be dry land.”

Kathleen Nichols: “We thought that there was just one flood. But now, with these results [Kathleen believes she found in dating the sediments that the bottommost sediment layer was 20,000 years older than the topmost layer], we can say with certainty, that this area has been repeatedly hit with cataclysmic megafloods again and again over a period of possibly 20,000 years.”

Narrator: “Despite the conflict between the catastrophic view of the Scablands and the standard view … we now know the truth is somewhere in between. There were huge catastrophes that carved out these giant landscape features, but they were part of the Missoula floods that repeatedly swept through this landscape.”

The case for just one Lake Missoula flood

There are problems with the interpretation of field observations as proposed above for many Missoula floods. Our Northwest team is convinced that the 39 backwater sediment layers in the Walla Walla River valley were laid down by a single Lake Missoula flood.

First, our team studied the pulsing flow concept. The floodwaters draining out of Washington were backed up, forming a giant lake behind nearby Wallula Gap on the Columbia River, because the narrow gap restricted the flow of water through it.

Our team determined that there was only one humongous Glacial Lake Missoula flood.

As more and more water backed up, a temporary lake formed and grew larger and larger. Floodwater from this growing lake moved up tributary rivers. Water backed 100 miles (160 km) up the Snake River and at least 25 miles (40 km) up the Walla Walla River. Huge volumes of sediment were dropped by this backwater flow in the Walla Walla River valley, which caused the water currents to shift and flow slower or stop in large areas, then return with increased speed later when restricted elsewhere (all the while keeping the whole valley under water).

This shifting produced a pulsing flow that laid down a series of 39 distinct sediment layers. The fastest flow brought in coarse sand, slower flow carried in fine sand and huge amounts of suspended silt made the water muddy at all rates of flow. The order of sediments dropped is repeated in each of the 39 layers, with coarse sand on the bottom, fine sand next and then a great thickness of silt on top. The distribution by grain size in each layer is about 1% coarse sand, 4% fine sand and 95% silt. The fact that 95% of each sediment layer is silt means that 95% of the time for each layer that area was covered by quiet standing water.

Now we are ready to discuss the ash layer, the second important feature studied by our team relating to the number of Missoula floods.

The Mount St. Helens ash layer lies within the large silt component of the 28th sediment layer. Silt settles out of water when it is standing quietly. If ash from an eruption of Mount St. Helens was falling into the flood backwaters, it would stay suspended much like the silt stayed suspended. When this backwater with suspended silt and ash slowed down to standing water, both of these very fine particles would begin to settle out. For the ash to settle out making a neat clear horizontal line of ash, it would have to be heavier and to have settled out in less time than the silt. From work done at Colorado State by Pierre Y. Julien and Guy Berthault (Fundamental Experiments on Stratification), we learned that as particles settle out, their settling rate depends on their density. Because ash is “heavier” than the silt, it would tend to settle faster to form a separate layer of ash within the slower settling silt.

The third feature of the 39 sediment layers in the Walla Walla River valley considered by our team was not brought up in the NOVA program. We found frequent vertical cracks cutting across all 39 sediment layers from the bottom to the top. The vertical cracks increase in width as they ascend and have percentages of coarse sand, fine sand and very fine silt, similar to the percentages in each sediment layer. A series of separate Missoula floods with dry periods between them could have produced mud cracks within separate layers, but this would not produce cracks bottom to top through all the layers. These bottom-to-top cracks could only form while all 39 sediment layers were still wet. As the backwaters were draining off, the water pressure from the floodwaters over the sediment layers would reduce to zero. With this pressure gone, the weight of the sediments would dewater the sediments by squeezing the water up through all of the sediment layers, carrying with it sand and silt and leaving it in ever-widening cracks called clastic dykes.

The conclusions from the evidence that we see

For the multiple Glacial Lake Missoula floods model, there is a problem with floods repeating every 40 years or so for 1,600 years. The Missoula flood is a late Ice Age melting stage event. With the Cordilleran Ice Sheet receding northward, would an ice lobe repeatedly dam up glacial melt water 39 times in the Clark Fork River?

Our team determined that there was only one humongous Glacial Lake Missoula flood. This conclusion was made in 1996 after research on site at the Burlingame Canyon rhythmite sediment layers in the Walla Walla River valley. The following year a Canadian team of scientists published their evidence for only one Glacial Lake Missoula flood.

The Glacial Lake Missoula flood and the global Genesis Flood of Noah’s time

Continuing research on the Lake Missoula flood and the Columbia River Basalt has brought to light many things in the field that give evidence for the global Genesis Flood and a young earth. Here are some exciting examples from the research being done. Pillow lava and marine sponge spicules found in the contact zones between individual layers of the Columbia River Basalt suggest that these lava layers flowed out under water and that the water was ocean water, not freshwater from a lake. This is strong evidence for the global Genesis Flood.

Is the earth young? Many examples continue to be found that show that the evidence in the sediment and rock layers do not support the millions of years given for the epochs, periods and eras of the standard geologic column. Extensive research by the RATE project [see RATE strikes at the heart of evolution], as presently done by an outstanding team of creation geologists and scientists, has found that dates determined by the standard radiometric dating methods cannot be substantiated.

The lack of erosion between various sediment and rock layers as observed by the flat surfaces between the layers can only mean that the succeeding layers were added quickly-entire sequences in a short period of time-before erosion could cut down into those surfaces. Examples include:

  1. The surfaces of the backwater rhythmite sediments in the Walla Walla River valley, though sometimes bent or with cross bedding within a layer, do not show erosion of top surfaces.
  2. The flat layers between the individual lava flows of the Columbia River Basalt in the Columbia River Gorge are without erosion.
  3. The flat sedimentary layers of the Grand Canyon are without erosion between them.

Many scientists accept the Bible as the inspired Word of God. We can be confident that the Bible is correct in matters where it touches on science, even though it was not written to be a science book. If there is a contradiction between science and the Bible, we need to look for the problem with science.

About the author

Dennis B. Bokovoy is in his eleventh year of teaching at Columbia Gorge Community College in The Dalles, Oregon, USA, where he teaches courses in physical and historical geology. He received his master’s degree in geology from Montana State University, Bozeman, Montana.


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