[QUOTE]Originally posted by TrueCreation:
[b]"Could you also please amplify a little more on how the canyon walls would stand if they are composed of recently (one year old) deposited sediments that are, by definition, water saturated?"
--Lithification, and pressures would have 'squeezed' water out of higher pressurizes areas of the grand canyon sediments. And they arent just one year old, they could be hundreds.[/QUOTE]
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Pressure acting on unlithified mud and lime... without confining pressure on all sides... would instantly turn the mud into a slurry, which would flow like... well... like a mudslide. Your understanding of lithification is lacking.
quote:
"Do you have examples of thousand foot cliffs composed of sand and mud anywhere in the world?"
--Forming? Nope, its kind of like the big bang, only happens once (not exactly correct but that's beside point). But yes there are ones in other places in the world. The Blue mountains of austrailia, and the Waimea Canyon may be considered. I'm not sure about Waimea Canyon though.
Blue Mountains:
"Sydney basin rocks are the most obvious when you look at the canyons and cliff lines, and make up the majority of the rock types present in the Blue Mountains. These rocks range in age from 290 to 230 million years old. There are three main layers to the Sydney basin rocks. These include: marine shales and mud stone at the bottom, coal measures, from which oil and coal was mined during the early development of the mountains. Above the coal measure layer is the most visible rock type of all, sandstone...
...capped with basalt, part of an ancient lava flow which occurred 14.6 to 17.7 million years ago. These basalt caps are all that remain of a vast sheet that once covered the majority the mountains, but has now almost all been eroded away. "
The question posed was... how could waterlogged sand and mud form a cliff?
Well, I don't think you can argue that these sediments were waterlogged after being covered with flood basalts. Therefore the canyon was cut AFTER the sediments lithifed, and AFTER the basalts cooled. You have found an example of a canyon that water erosion alone cannot explain. Basalt is almost totally impervious to water. Chemical erosion is necessary to break down the tough igneous matrix. Plus lots of time. The best combination is a lush vegetative cover, lots or moisture, and a deep topsoil. These produce lots of humic and carbonic acid to break down the rock. In a Flood, you get plenty of water, but not the other two, thus no chemical erosion to speak of... certainly not in a year. The Flood waters would just run off.
Waimea Canyon:
"Formed by deep incision of the Waimea River into tholeiitic and post-shield alkalic lavas of the Waimea Canyon Basalt"
http://www.wsu.edu/~reiners/tour/wc.html
"The Makaweli Member (green), at 4.16-3.92 my, fills a down-dropped fault-like feature known as the Makaweli Graben.
Notice the canyon cutting into the Makaweli member visible in the cross-section at the bottom.
"The Makaweli and Olokele members are MOSTLY tholeiitic basalts that are thick and ponded... "
I think you'd have a hard time finding a tougher, more resistant rock to carve a canyon into in a short period of time using only the erosive power of rainwater.
These two examples are the exact OPPOSITE of a canyon cut into soft, unlithified sediment...
[This message has been edited by wehappyfew, 06-06-2002]