Saturday, January 24, 2009

The Disaster of the Niagara Tunnel - Part 4

Part 1, Part 2 Part 3

I'll actually be saving this in draft, to accumulate some text, which is something I usually cannot do (I have to blab everything as soon as possible!)

As I've said, formational micro-shear is what makes this rock the sinister spawn of the devil, (I'm going this route, in case they try to suck me into their billion dollar lawsuit. Who would want a nut-case?).

The Queenston Shale formed after the giant mountain ranges of the Precambrian finally sunk back into the sea. As we recall, our Ontario Megathrust Faults were involved in the creation of the mountains, but they also entered into obscurity.

So, at the end of this orgy of mountain building (orogeny...orgy... get it? ha, Ha!... Ow my back!), we had a big peaceful inland sea. You may wonder, how come we had all these inland seas, and don't have them now? It's because, as Darwin noted, continents go up and down like big hot air balloons. One moment they override a hot piece of mantle ... up!, and the next they go over some very cold slabs ... down!

So, the main mountain building activity was during the next collision, just east of this inland sea. At times, a huge rush of sediment came in, with slits and clays, which formed the shale. Then everything was still for a long time, and it rained down kettle scale, like the stuff I just cleaned out of my water cooler, -- yuck!. This formed the limestone layers.

Well, there were more continental collisions and this stuff was buried and baked. None of it was uniform, like a big hunk of limestone. No, everything hardened at different rates, lots of fluid motion, internal shearing, etc. The results can be viewed in the Scanning Electron Microscope (SEM) slides.

In relatively recent times, this rock has been squeezed tightly by continental high horizontal stresses, most likely associated with regional tectonic motions. It's all made for a complex mess!

So, imagine that we have a giant Star Trek transporter that can take a 50 foot cube of rock, and place it in our laboratory. If we go to normal rock, such as granite, or the chalk of the English Channel, we can pre-instrument the cube, haul it out and place it on our frictionless surface. We would find that the rock would expand, due to the confining stresses being removed. We could recompress the rock with giant presses, back to its original size, and that would be a measure of the in-situ stresses. The rock is elastic!

Not so the Devil Rock! If we took it out and instrumented it, we would find that it slowly expands like compressed cellophane, with great crackling. Slowly, vertical joints would appear out of nowhere, along hidden micro-alignments. The rock would undergo a great transformation, and we could never squeeze it back into it's original state. The rock would continue to expand for months!

-- damn back!

No comments: