otseng wrote:Questions which I'd like to discuss:
1) Where did the water come from?
2) If a catastrophic flood created the Scablands in a short period of time, couldn't other geological features elsewhere be also created in a short amount of time?
This is an interesting story, and one I am very familiar with. It is a great example of the value of history of science too in understanding the true nature of how science as a human adventure is actually carried out within the community of scientists. I will be in future posts drawing upon an excellent resource, John Allen and Majorie Burns book called
Cataclysms of the Columbia.
We now know conclusively the source of the water. It was first revealed in a rather low key paper entitled "Unusual Currents in Lake Missoula" presented at a Geological Society of Washington meeting in 1927. In this meeting, a fellow named Thomas Pardee purportedly turned to his friend and said, "I know where Bretz's flood came from." (Allen 2002: 56) Purdee argued that a great ice dam created by the encroaching "lobe of the Cordilleran glacier" which plugged the drainage of the Clark Fork River, and that eventually "The ice cam is thought to have failed." (Allen 63) It was so low key because he made no point of highlighting the size of both the ice dam and the resulting flood from its failure. He stated his evidence in a low-key matter of fact way. Perhaps he was seeking to avoid some of the wrath of his more conservative fellows, who were wedded ideologically to "Uniformitarianism," a rather dogmatic idea that the present is an indication of the past, that cataclysmic events did not happen geologically speaking. Alfred Wegener faced the same
uniformitarian dogma when he proposed continental drift. Like Wegener, Bretz examined the evidence, and developed his theory based upon the evidence, even though he did not have the knowledge that Purdee did regarding the source of water, just as Wegener did not have a good explanation for the mechanism driving continental drift. Wegener's ideas were eventually provided a mechanism by Jolly and Holmes, while Bretz had Purdee to provide the source of his water. After describing certain "measurable fact about the lake," such as its altitude had reached "about 2000 feet higher than the floor of the valley just above the dam," he went on to add in a rather low key manner that this "permitted a sudden large outflow."
Eventually, Bretz was vindicated and Purdee's theory was further supported by geological evidence gathered from a 1952 field expedition that resulted in two significant publications on the subject. (Allen et al. 2002: 67) The following is a rather interesting summation of the situation:
Allan et al. wrote:Early [Biblical] Catastrophism gave way to Uniformitarianism, which expanded our concept of time but stopped us from thinking in terms of sudden change. Then came Bretz's flood and with it still newer ways of perceiving, ways that include Uniformitarian ideas. You see, there's a great deal of sense in the idea of steady, imperceptible change. Most geology (from our limited, human viewpoint) works that way. And, the truth is, all those events we call "Catastrophic" are only the end result of slow processes building to rare but dramatic conclusions. Like the grand collapse of a carefully arranged row of dominoes, catastrophes are nothing more than finales. (Allen et al. 2002: 72)
In geology, believing is seeing. We're able to "see" catastrophes now. It was Bretz's Scabland that started the trend. Alfred Wegener's long-maligned theory, leading to "plate tectonics," (with a story more intricate than Bretz's) has at last been taken to heart, and we can no longer consider the earth secure. The continents, we're told, are drifting, and the ocean basins are on the move. Africa and South America probably did once fit together, just as their jigsaw shapes suggest, and the West Coast of North America is apparently an alien piece of the Mid-Pacific that began to be shoved into the American continent back in the Mesozoic, 100 million years ago. (Allen et al. 2002: 72)
Nothing stays put. A mere 5 million years ago the dried-up basin of the Mediterranean Sea was cataclysmically filled when then Atlantic Ocean broke through a natural dam at Gibraltar. (Allen et al. 2002: 72)
I have a question for you Otseng. When did the scientific community first confirm that the Medditerranean Sea (Basin) was once a desert? And how did they discover this? For that is an example of your second question.
Hint:
Hsü wrote:The Deluge
Cita, Wezel, and Maync had all been taught more than the rudiments of Mediterranean geology. They were all familiar with the various occurrences of evaporites on the land surrounding this inland sea--the late Miocene evaporates in Spain, in Piedmont, in Tuscany, in Marche-Umbria, in Calabria, in Sicily, on Ionian Islands, on Crete, on Cyprus, in Israel, in Algeria, and so on. Like others in our profession, however, they had considered these local logoonal deposits, formed during an epoch of unusually dry climate. As we now steamed eastward, relieved from the tension of daily drilling operations, the significance of our discovery began to sink in: we had found an evaporite formation beneath the Mediterranean sea floor, and we had geophysical evidence to suggest that the whole Mediterranean was underlain by this formation. With this knowledge we could no longer dismiss the late Miocene evaporites on land as simply local deposits. (Hsü 1983: 111)
Both Cita and Wezel had studied the evaporite formation in Sicily, the solfifera sicilienne, and knew it to include a thick series of rock salts, gypsum, and anhydrite. Interbedded with evaporites were marls with Messinian fossils. The youngest evaporite formation from other circum-Mediterranean countries were also Messinian in age. Unfortunately, the fossils in our cores from Hole 124 were not very good, and Cita had not yet had a chance to take a close look at them. She was eager to get some better samples at our next site to confirm the Messinian age of the evaporite deposition in the Mediterranian. (Hsü 1983: 112)
The solfifera in Sicily is overlain by a white oceanic sediment called Trubi marl. This marl has a microfauna that could have lived only in a deep sea of normal salinity. Paleontologists are quite certain of their conclusions: The Trubi foraminifera belong either to species that swam in deep waters or genera that dwelled on the deep and cold sea bottom. Later we were told by Dick Benson of the Smithsonian Museum, a specialist in ostracods, that the Trubi marine ostracod fauna in this formation is also a typically cold water assemblage, similar to those forms that live in the deep Atlantic today. Yet as the editor of Sedimentology, I had ust porcessed, prior to my depature for Lisbon, a manuscript by Laurie Hardie and Hans Eugster of the John Hopkins University on the solfifera sicilienne, which claimed that the Sicilian salts were laid down on a playa. If both the sedimentologists and the paleontologists were correct, the inescapable conclusion would be that the Messinian salt deposition in Sicily had been ended by a sudden deluge. When marine waters returned, the salt pan was turned suddenly into a deep sea. At the previous site we had failed to obtain a core that recorded the passage form evaporite to normal marine sedimentation. Nevertheless our oldest Pliocence core there showed considerable similarity to the Trubi marl of Sicily. Was it a clue that the deluge was not a local event in Sicily? Perhaps the whole Mediterranean was drowned when the floodgate of Gibralter was crushed. The evidence was tantalizing, but we hd to be sure. There was no alternative but to sample meter by meter at our next site with continuous coring. (Hsü 1983: 112-113)
(....) After the cores were investigated and the data processed, it turned out that we did not fare too badly at Site 125. Combining the cores from the two borewholes at this site, we managed to put together a continuous section for the sedimentary record of the last 5 million years, just as we had hoped. And more important, we obtained a core that recorded the end of the evaporite deposition and the beginning of the deluge. The last sediments of the Miocene were carbonate mud, which contained only very poorly developed forms of marine organisms. We now interpret this mud as the sediment laid down during the transient stage when the desiccated Mediterranean was again filled up. The salinity of this rising sea must have been higher than normal, for unlike the present situation, where heavy birnes produced in the Mediterranean by excess evaporation can find their way back to the Atlantic through the Strait of Gibralter, the latest Miocence Gibralter was the site of a huge waterfall, a one-way street. There was no way for the heavey brines to flow back into the Atlantic. The salt water grew more and more salty under the hot and sunny Mediteranean sky so that only some dwarf microfaunas could survive. Those were the last of the Miocene Mediterranean creatures. (Hsü 1983: 116)
Suddeenly, at the end of the Miocene, the dam broke and the basin was quickly filled to the brim. Then the influx of the Atlantic water and the reflux (return-flow) of the Mediterranean brines were able to moderate the high Mediterranean salinity caused by evaporation. The Mediterranean became again a habitable environment for marine organisms. (Hsü 1983: 116)
-- Hsü, Kenneth J. The Mediterranean was a Desert: A Voyage of the Glomar Challenger. Princeton: Princeton University Press; 1983; c1983 pp. 111-112.
