 One of the ways we record data about sedimentary rocks is by using a stratigraphic column. So it's a graphical representation of the rocks. And so we have a vertical axis, which is the scale. And so this is the thickness of the rock unit. So for example in this image over here, the pen is 15 centimeters long approximately. And so if I was going to draw this rock or graphically represented at the same scale, I might go from zero here to something like 15 centimeters up here. If you are measuring much thicker rocks, you'd change the scale for that. And then across the x-axis here, we have the grain size. So what this does is it allows us to record the grain size graphically with the thickness of the rock. And also within this layer we'll draw the beds relative to the grain size and we'll also include the sedimentary structures that are present. So as an example, I am going to, I don't know exactly what the grain size is in this image, but I'm going to say basically this whole area in through here is very fine sand. And it is 15 centimeters thick. It varies a little bit. So what I would do is the bottom of the image is here. Those are across here. And if I had 15 centimeters of very fine sand, I would draw a vertical line to 15 centimeters, which I'm not actually, oh my goodness, not actually drawing it straight, but pretend it is. And then I would describe the sedimentary structures in this sand. Now there are some faint laminations and then there are also these circular areas that the arrows are pointing to. And these are burrows that are filled with coarser sand. And then there's some faint plain or lamination. So I'm going to make a legend and define these. So I'm going to say my burrows are going to be this little squiggle. And a faint plain or lamination. I'm going to draw as one line with another line underneath it like that. So then what I would do is I would draw some burrows in here. And with my tablet, they're a little bit look a little bit different. Let's make that one a little more curvy. I have to exaggerate the curves here. It looks like there may be quite a few in this zone here. So I'll maybe add a couple. There's one right at the boundary here, but not very many near the top. So maybe I'll add I'll add a couple in here. And there's actually more planar of the faint planar lamination at the top. So I'm going to add that symbol in here. And there's a little bit down in the zone here right below where there are lots of burrows. We're going to add that symbol here. And there's not much below that. Okay. So now I've drawn my stratigraphic column representing the sediments up to here. So there's this burrow sitting right here. And then we have this wavy line here. And this is medium sand here. And then it goes back to the very fine sand up here. So we have maybe three centimeters or so of the medium sand. One, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15. We're going to start our zero right here since I didn't actually count 15 up. And so that means each one of these lines represents one centimeter. So there's a little bit of variation on this surface. So I'm going to draw it as a wavy line. And then the grain size is medium sand. So that's this line right here. So I'm going to trace it going up. Okay, I drew it to the right one here. And then I have let's say three centimeters or two and a half centimeters of medium sand. But then there's a gradation into the very fine sand, but mostly at the top. So we have one centimeter, two centimeters, and it grades back to the very fine sand. And say that goes up another centimeter. So you don't really see any sedimentary structures in there. So I could put some dots in for sand if I wanted, but that duplicates this end out here. And notice that I drew this as a curved line here. And that means that it's a gradational change. Then at the top of this very fine sand bed, the green arrow here is pointing to a flame structure, which is a deformation feature related to dewatering of the finer sediment below the coarser sediment. So you can see that the layer varies. And then we have some really nice planar lamination, which my line did not actually follow there. And so we have two new things to add to our legend. We have flame structures. And I'm going to draw them like that. And then we have a well developed planar lamination. I'm just going to call it planar lamination. And because it's better developed, I'm going to do two lines that are parallel, whereas this one has the break in it. So first on top, we have an abrupt change. And I think this is medium sand again. So I'm going to draw a contact that goes out to medium sand. And then we have the flame structure. So I'm going to draw a flame structure like that here. And maybe there's some planar lamination over here now that now that I look at it a little bit more closely, I'll call that some some faint planar lamination in this right here. So that's the lines with the break over it. And maybe, maybe within the fine sand as well. So then the medium sand is again, let's say up to here is about four centimeters thick. One, two, and it definitely has the planar lamination in the upper parts of it there. And up at the top here. And then it's a little bit hard to see in this rock what we have. So, and I should say that when I have, when I show a line coming out like this, like this one, it's an abrupt change in the grain size. So this one is also abrupt. That means that there's a really distinct line between the two of us. And then this waviness is a bad drawing. So what we end up with is a graphical representation of a rock. And what this means is that it's recording our observations of what we can see in the field. And then it allows us to compare rocks from one site to another with the key features recorded within the stratigraphic column. Thanks for watching.