lpetrich

Noah's Flood may be pure fiction, but the Earth has had some big floods, even if not planetwide ones.

Here's a nice site on the<a href="http://www2.opb.org/ofg/1001/missoula/index.htm" target="_blank">Missoula Floods</a>, sometimes called the Spokane Floods. These floods happened toward the end of the last Ice Age, about 15000-11000 years ago, in the Pacific Northwest US. A glacier in the Idaho Panhandle would act as a dam, creating Lake Missoula. Eventually, however, the lake's water would melt some of the glacier, leaking out and causing a catastrophic dam break. This lake would then race down to the Pacific Ocean in the Columbia River basin over a few days, traveling at something like 60-90 mph (100-130 kph).

This lake formation and glacier-dam break would happen repeatedly, about once every 35-55 years, and the result was the carving of the Channeled Scablands terrain in eastern Washington. Some of the land has ripples that look much like river-bottom mud ripples, but which are much bigger.

The first to propose the occurrence of these giant floods was J Harlen Bretz (no . after the J) in the 1920's. However, the rest of the geological community insisted on an overzealous application of Uniformitarianism, insisting that only presently-observable processes could be responsible for that terrain. This was usually a very successful principle in geology, and it can be interpreted as a version of Occam's Razor. But geologists nicked themselves rather badly with it here.

However, in the 1950's and 1960's, other geologists started exploring the area, and they ended up acknowledging that JHB had been right.

Have there been other such big floods? Yes, and they took place at about the same time.

In northern Utah, the Great Salt Lake had once been the much bigger Lake Bonneville. And about 14,000 years ago, its water broke through the Red Rock Pass in Idaho, flowing down the Snake and Columbia rivers.

Also at this time, there were some similar floods in the Altai Mountains in Siberia.

Here's a <a href="http://www.geo.arizona.edu/palynology/geos462/04floods.html" target="_blank">nice summary page</a> on the Missoula, Bonneville, and Siberian glacial-dam-break floods.

Such floods may have happened elsewhere in the Solar System. On Mars, there are numerous now-dry river valleys -- which look much like the Channeled Scablands. This means that something or other had caused giant floods on Mars.

But what? This has often been guessed to be water, but that would require that Mars have a very thick atmosphere in the past, in order to create the necessary greenhouse to trap enough heat to liquefy water.

Here's an <a href="http://www.spacedaily.com/news/mars-water-science-00k1.html" target="_blank">alternative hypothesis</a>, that the channel-carving substance had been flows of carbon dioxide with dust released from the surface. This has the nice property of not requiring Mars to be hot enough to liquefy water.

It also means that the only places that could have liquid water are subsurface places, which are rather hard to explore. So Mars's surface may always have been lifeless.

pseudobug

Nice links,Ipterich. Thanks.

After reading the first link, the Missoula Floods, I thought it was striking how Brentz's story had sort of Barbara McClintock ring to it.

IT is interesting how occasionally the ability of those who are able to interpret their observations and experiments in a manner counter to widely held theories can alter basic concepts of a field of study. IT is also not surprising that some "elders" of a particularly field of study do not accept the "radical" concepts. After all, those "elders" quite likely made their name by contributing to the development of the accepted school of thought in a specific discipline.

The thing about science that is great is the acceptance of evidence or data. Scientists may be a hardheaded, prideful lot at times, but most long-held concepts shown to be misinterpretations don't stand up too well in the face of convincing experimental evidence.

Some of the trolls such as randman who claim that scientists "supress" data and "censor" those who hold unpopular theories would do well to read the "Missoulla link". They should note that it states that Brentz published his controversial idea early on. They should also note that Brentz had a hypothesis that could be confirimed by either experimental evidence or observation and interpretation of historical evidence. These are two things that the proponents of a certain so-called "theory" of intelligent design don't seem to have. They do, however, love to cry about their ideas not getting a fair shake by science.

lpetrich

In McClintock's case, much of the skepticism was "how does this fit into what we know about genetics?" So it got set aside until mainstream biologists started discovering jumping genes in bacteria, yeast, and fruit flies -- which are smaller and have shorter generation times than corn plants.

Also, it would be interesting to see why uniformitarianism triumphed over catastrophism in the 19th cy., where catastrophism is the view that the Earth has experienced catastrophes that have never happened in humanity's better-documented history. Lyell had done something of a rhetorical snow job with various sorts of uniformitarianism: U of natural law, U of processes, and U of rates. However, U led to testable hypotheses much easier than catastrophism did, at least back then.

Thus, one can test the Principle of Superposition by finding out whether features in rocks like mud cracks and footprints extend downwards the way that present-day ones do.

However, U was held to include some catastrophes, such as volcanic eruptions, because the occurrence of such eruptions is well-documented.

But the past half-century has seen a miniature revival of catastrophism, most likely with the greater sophistication of the field. Big catastrophes have become testable hypotheses!

This has led to the acceptance of the existence of not only giant floods, but also big meteorite strikes.

The ultimate example of the latter has emerged as a favorite theory for the origin of the Moon. The "Big Whack" theory proposes that, early in the Solar System's history, a Mars-sized object had struck the Earth, splattering some of its outer layers into orbit. This produced a big ring of rock droplets, which condensed to form the Moon.

This explains some oddities of the Moon's composition:

Though it it is not much smaller than the inner planets, it does not have an iron core.

The Moon has very little of volatile substances like water, meaning that it had once been baked dry.

Here's <a href="http://planetaryweb.ucl.ac.uk/student/work/moon/origins.htm" target="_blank">a more detailed and somewhat technical discussion</a>.

Dr.GH

Thanks for pointing out the flood information.

However, 18th and 19th century catastrophism was basicly Biblical "flood geology" and uniformitarianism was the notion that the earth shaping mechanisms (and by extention chemistry and physics) in the past were the same as today.

lpetrich

Actually, early-19th-cy. catastrophism posited the occurrence of a long series of catastrophes, with only the most recent one possibly being Noah's Flood.

lpetrich

Just in at Science magazine, <a href="http://www.sciencemag.org" target="_blank">http://www.sciencemag.org</a> :

EARTH SCIENCES:
The Study of Superfloods
Victor R. Baker
Science Mar 29 2002: 2379-2380

The exact subject of this thread.

In particular, judging from seafloor evidence, there had likely been big floods in Oregon's Columbia River valley for the last 2 million years.

ps418

Absolutely. The 'Missoula Flood' wasn't a one time thing, and it didnt occur only at the end of the last glaciation. According to a ref cited in the article, the Missoula and Altai superfloods reached peak discharge rates up to 20 million m3 per second, which means that at the peak of the flood, much more water was being discharged into the Columbia Basin than is normally discharged from all the rivers of the world. Here are the abstracts to two of the articles referenced in the Science article, discussing the record of mass-flow events:

Zuffa et al., 2000. Turbidite Megabeds in an Oceanic Rift Valley Recording Jökulhlaups of Late Pleistocene Glacial Lakes of the Western United States. Journal of Geology 10, pp. 253-274

Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one 60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jökulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.

Bjornstad et al., 2001. Long History of Pre-Wisconsin, Ice Age Cataclysmic Floods: Evidence from Southeastern Washington State. Journal of Geology 109, pp. 695-713.

Cataclysmic Ice Age floods in the Pacific Northwest began as early as 1.52.5 Ma, on the basis of an evaluation of surface exposures and recent borehole studies within southeastern Washington. Field evidence suggests at least two episodes of pre-Wisconsin (i.e., &gt;130 ka) glacial-outburst flooding. A Middle Pleistocene flood is identified by normal magnetic polarity, calcrete-capped deposits that yield maximum Th/U age dates from 200 to &gt;400 ka. The deposits with reversed polarity are correlated to Early Pleistocene (&gt;780 ka) floods. While exposures of pre-Wisconsin deposits are limited because of erosion and/or burial, the record of earlier Pleistocene flooding is preserved within giant flood bars. These bars show incremental growth, representing a composite from cataclysmic floods deposited intermittently through the Pleistocene. In one giant flood bar, up to 100 m thick, deposits interpreted as Matuyama age indicate that the bar had grown to half its present height by 780 ka. Furthermore, Matuyama-age, reversed-polarity flood deposits may be underlain by up to another 15 m of normally magnetized deposits at the base of the flood sequence. This normal-polarity interval appears to be associated with Early Pleistocene cataclysmic floods, perhaps of Olduvai age (&gt;1.77 Ma). Many of the features associated with cataclysmic floods, such as coulees, giant bars, and streamlined loess hills, may have been established during the Early Pleistocene and were only slightly modified by up to hundreds of subsequent flood episodes.