 The picture you're looking at is a diagram of layers of rock in the earth. You might see something like this in a wonderful cliff, or if you could dig a giant hole with a cliff for an excavation in the side of a building foundation or something like that. What you see is that the layers of rock are not flat and uniform and boring. They've been broken and tilted and there's all sorts of action has happened. Now layers of sedimentary rock are put down initially almost horizontally. So there must be an interesting story as how the layers came to look like this. So let's take a look at that history through millions of years of activity. First of all, sediment is deposited in horizontal layers. Changes in environment over time will make those layers somewhat different. And so we get the rock layers that you see labeled Z and Y and X. Then something happens, a mountain building event, whether the rocks are squeezed and folded or something that starts to tip the layers. At the same time, erosion is happening. The layers may have been raised out of the sea or out of the river valley. And so erosion is happening, making an unconformity on top. And so you can see the action going on as wind and rain wear away the rocks and the rocks are tilted by the moving plates of the earth. More sedimentation happens, maybe sea level rises and floods it, maybe rivers are bringing things down from the mountains. And so you're burying that erosion surface under new material that you see as rock layers W and V. Finally, there's a big earthquake, a climax event, and you get the things broken in this beautiful fault line U that comes across the diagram. And now you're left with what you see in the cliff. If you'd like to review that very briefly, just roll your mouse over the letter on the diagram that you're interested in and it will give you a very short blurb of what happened.