 bottom of the Grand Canyon, deep in its channel, flowing out of the Page Torch is a glorious Colorado River. And next to the river, there are rocks that were sediments, they have been lava flows and other things, they have been bent in the heart of a mountain range, they've been intruded by granites, they have had the heck beat out of them. And on top of them, there is an unconformity, an erosion surface. Sitting on top of that erosion surface, there are various sedimentary rocks, things that formed on the edges of the sea, um, interbed with lava flows. There are many erosion surfaces within that pile of sedimentary rocks. And that is an immense pile of sedimentary rocks, it has been dropped down by faults. If you actually try to measure the thing, you find that you get some thickness and then you walk along the layer and then you measure some more thickness. And the total thickness is actually about two miles of sediments in that pile. And then on top of that, there is another erosion surface. That was the Grand Canyon Supergroup in that two-mile pile. Sitting on top of this, the sea came in and you end up with the, um, Tapeed Sandstone and you get the Bright Angel Shale and you get the Mu'ov Limestone. And then sitting on top of that, there was erosion, there are deep channels in places that were cut on top. In those channels, one goes in and finds little bits of pockets of the Mu'ov Limestone sitting in there. The sea had come in, the sea goes out, the sea comes back and puts in the Mu'ov. It goes out and erodes again. And then you get the giant red wall, the great massive red wall. And the top of that is also eroded and it has some channels. And it wasn't until the 1980s when real helicopter geology came in that people realized that in fact some of those channels have little bits of limestone in them called the Surprise Canyon. The sea had gone out, it came back and put that down, it goes out and there's erosion again. And then sitting on top of this, we get the great rocks of the Supi. The Supi is ocean sediments, limestones to the west, and it is, um, a delta, it's up on land to the east, there's about four different units and there's an erosion surface that goes at the end of each of those different units of the Supi. The Supi then gave way to the mighty cliff of the Coconino. This is the sand dune rocks. This is the one that has all the beautiful tracks in it and so on. And on top of that there's another erosion surface. Then there's sort of a mix of land and sea sediments. It's known as the Toro Weep that makes a bit of a slope and it has an unconformity and erosion surface. And then sitting on top of this is the cliff of the Kayabab Limestone which gets up to the villages where you can go as a tourist. But if this in turn slants down to the north and underneath that you're going to find Zion way up there and then you're going to find Bryce and so on up through the giant pile of rocks.