In a recent two part article I introduced the reader to one of the great natural events in Earth history – the mighty Bonneville Flood. However, as I made clear, this enormous fluvial event was only a regional manifestation of a much larger event, one of such scale and magnitude that it almost defies comprehension. In this article I will begin to tie the Bonneville Flood into that larger event, or series of events actually, that so profoundly altered the late Pleistocene/Paleolithic world and made way for the world we now inhabit, the Holocene. I write this because the imperative of our time is that mankind becomes aware of the catastrophic history out of which our species, and our civilization emerged.
I write this because the imperative of our time is that mankind becomes aware of the catastrophic history out of which our species, and our civilization emerged.
The scenario that is now emerging from a veritable wealth of evidence from multiple sources shows us that in the time period around the end of the last ice age, roughly from 12,000 to 14,000 years ago a series of unimaginably gigantic floods swept over large portions of the Earth’s surface. These floods were the result of what can accurately be described as flash melting of the massive ice sheets that covered virtually all of Canada, the northern U.S. and large sections of northwestern Europe. These melting episodes happened so fast that when a group of scientists back in the early to mid-1970s first realized the speed at which they occurred they were at a loss to explain the source of the enormous amount of energy required to convert uncountable thousands of cubic miles of glacial ice into meltwater in a geological instant. The puzzle they confronted when they realized the swiftness at which the vast ice sheets disappeared they called the “energy paradox.”
[See: Andrews, J. T. (1973) The Wisconsin Laurentide Ice Sheet: Dispersal Centers, Problems of Rates of Retreat, and Climatic Implications: Arctic and Alpine Research, Vol. 5, pp. 195-199 and Hare, Kenneth F. (1976) Late Pleistocene and Holocene Climate: Some Persistent Problems: Quaternary Research, Vol. 6, pp. 507-517.]
Note the understated wording in both titles referenced above: “Problems of Rates of Retreat” and “Some Persistent Problems.”
I will address the problem of the energy paradox in more detail in future installments.
Unable to resolve the question of energy sources the researchers decided that they would postpone dealing with it until more data was available and would, at some future date, get back to it. However, since that time the question has been mostly forgotten as politics has come to dominate the discussion of global change and it is unlikely the source of the necessary heat energy could be blamed on carbon dioxide.
Within the past decade new evidence has emerged that could shed light on the cause of what is nothing less than one of the truly extreme catastrophes in the history of the Earth. That evidence for that cause I will take up in another article. For now I am going to describe some of the effects that this catastrophe had upon the landscape of North America, for it would appear that some of the most dramatic and intense manifestations of these events around the planet were centered upon North America.
At the conclusion of the article on the Bonneville Flood, I described how after gashing its way through Hells Canyon, it turned west at Lewiston, Idaho, and, to quote from that article, it was at this spot “that something truly astounding happened. Here the waters of the Bonneville Flood met those of the Great Missoula Flood, a monstrous fluvial event that exceeded in size and scope that of the Bonneville Flood by more than a full order of magnitude.”
The discovery of the Missoula Flood, and the controversy that ensued, is one of the most interesting and important in the history of geological science. It encompasses the saga of one of the truly heroic figures of 20th century geology, J Harlan Bretz. The story of Bretz and his original discoveries from the early 1920s to the late 1960s is well told in Graham Hancock’s latest book, Magicians of the Gods, which I would highly recommend to anyone who wishes to delve deeper into this fascinating and important story. So rather than cover that ground here I will go directly to the epic tale encoded into the landscape itself.
So, what is so astounding about what happened at Lewiston, Idaho?
An image below is a photo of an outcrop in a gravel pit just south of Lewiston along the Snake River. The place is called Tammany Bar because at this location a small stream called Tammany Creek flows into the Snake River. What could possibly be interesting about a gravel pit, you might be asking. It so happens that through the quarrying operations in this gravel pit, the internal architecture of a gigantic landscape feature is being exposed, revealing a sequence of events that can only be described as mind-boggling.
To understand the explanation that follows consider this: If you have ever walked along a creek or a river, especially after a rainstorm, you will see sand bars, sometimes gravel bars if the water flow was vigorous enough. Typically these bars occur on the inside of a meander, or bend, because the water of a creek or river actually flows slower on the inside of a curve in the channel and faster on the outside.
That is because in both zones the water is trying to stay in pace with the average flow of the creek as a whole. This means speeding up where the path of the water molecules is longer and slowing down where it is shorter. When water flow speeds up it tends to pick up and transport sediment, if sediment is available, and when it slows down it tends to deposit that sediment. That is why creeks and rivers build their sand bars on the insides of curves. I would urge you to do some exploring in a local creek and you will see what I am talking about for yourself. Frequently, on the channel side opposite to a sand bar the channel bank will be vertical, oft times even undercut because of erosion by the faster moving water.
It is a huge gravel bar deposited along the inside of a curve on the Snake River. Please go to Google Earth, type in Lewiston, Idaho and you will be able to see the Snake River coming from the south with Lewiston on the east and Clarkston on the west side of the river right where it makes a sharp bend to the west. At this location the Clearwater River comes in from the east and joins the Snake. About three miles south of this junction, on the east side of the Snake, just on the outskirts of Lewiston, is the northern tip of Tammany Bar. This feature is clearly discernible as it wraps around the curve in the river. In Google Earth you can navigate around viewing the bar from various heights and angles.
In the case of Tammany Bar the feature in question is nearly three miles long and a half mile at its greatest width. As the Bonneville flood tore through Hells Canyon it picked up millions of tons of debris, boulders, broken rock, gravel, sand, silt and anything else in its path and as it exited the canyon mouth and slowed down in speed it began laying down its sediment load. Tammany Bar is a result. Of course the floodwaters did not stop there, they ultimately ended up in the Pacific Ocean via the Columbia River.
The material composing the bar is a wide assortment of sand, gravel, boulders and undoubtedly the remnants of organic material picked up along the flood route. For years there has been a quarrying operation working the north end of the bar, extracting and sorting the different kinds of sand and gravel material for a variety of purposes.
Over the years I have visited this quarry multiple times to ascertain the nature of the sediments composing the great bar in order to learn what they can teach about the nature of the flood which created them. In the next photo we see a man standing in front of a shear wall of mostly grey gravel exposed in the quarry. Looking close you will notice that it is not just a featureless mass. It has a very definite structure. We can see that it has bedding. We can also see that the bedding is tilted and this tilting angles downward from right to left. This is called foreset bedding in geological lingo and it is an indication of which direction the current was flowing. The bedding tilts down in the direction of current flow, so we can see that the current came from the right, which, in this case, is from the south. We can also see that the gravel layers seem to be organized into ‘packages’ of bedded gravel.
What we are looking at is the result of colossal surges of sediment choked flood water, pulses if you will, and coming right after one another in sequence. These in turn are part of larger surges, pulses within pulses, each shearing off the deposits laid down by the preceding pulse and dumping more debris on top, the process repeating itself multiple times.
This material was stripped from the antediluvian landscape by the extreme force of the Bonneville Flood as it swept across the Snake River Plain of southern Idaho and through Hells Canyon, some of it originating hundreds of miles away.
As remarkable as this feature is, what is really interesting is what you can’t see in the picture above the gravel layers, but that must wait for Part Two.
Thank you and Godspeed! – Randal and Camron (Astromonk) ]
[editors note] Learn a bit more about the region and taking in the incredible scale of the geological features left in the wake of the global superflood of ~13k BP here.
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