PrintASHLEE DERE: OK. Now that we've described everything about each horizon, we can give each horizon a name. And this allows us to quickly identify what part of the soil each horizon is from. So if we look at this first horizon, we have what's called an A. That the master horizon. That's the surface soil. Then we're going to further describe it with a little p, which means it has been plowed or disturbed, and we know that we're on a farm. So it has been, in the past, disturbed by humans.
So now we've got this described. Now we can move to our second horizon here. And what we saw about that is there was quite a bit of increase in clay. We went from 22% clay here to 36% clay. So we definitely have more soil development. Another indication was that structure. We saw a shift from this granular, little structure to bigger, subangular pieces. So we have definitely soil development going on. And the soil development part of the profile is indicated by a B. So that's the next horizon. So B horizons indicate that there's development.
What we can do now to further describe that is look for clay films. And clay films are accumulations of illuvial clay, meaning that the clay has washed down from the top of the soil. So if we find those in this horizon, then we can further describe it by adding a little t. And that's the symbol for an illuvial accumulation of clay. Something that's moved into this horizon from elsewhere.
So if we pull out some samples, we can look more closely. Usually a hand lens is a really good tool to have for this, but sometimes you can just see then with your bare eye. So look closely. A lot of times the clay will accumulate where there's roots. So it'll just kind of settle in root channels. And on the face of these peds.
TIM WHITE: Do you see any?
ASHLEE DERE: I do see some. Do you?
TIM WHITE: Tiny.
ASHLEE DERE: Tiny. They are very tiny, but they are there. And that's the important part is that they are. And we can see a little bit in the actual profile itself.
TIM WHITE: So I'll put a t.
ASHLEE DERE: We'll have a little t. So this horizon is defined as a developing horizon with clay that has come in from elsewhere. So now we have this third horizon. And where we saw these little clay films very sparsely throughout this upper horizon, we see everywhere down here. All these glistening little points.
If you bring out a piece, you see it kind of shimmers in the sun. And that's all clay. It's kind of like it's been painted over the soil. And those are called clay films. And there are excellent examples in this horizon. So we definitely know, again, we have a developing horizon. And it's further described with a t.
It's got a lot of illuvial clay coming down. So as this profile forms and rain comes down, it drags that clay down and it accumulates toward the bottom of the profile. That's why we have so much more here. And we also saw that when we textured the soil. There's considerably more clay, again, in this horizon than in the upper horizon.
And all that leaves us now is this rock at the bottom. And all we can describe that as is R. A big R is the master horizon here. And there's no further description for this. And you can often note what kind of rock it is, which is helpful. But we've got limestone here.
TIM WHITE: That might have to do with the rocks.
ASHLEE DERE: You should do the rocks. That is your discipline. This is a really good example of a residual soil, where the parent material is dominating what's forming here. And then also the climate. All that clay that we see being washed to the bottom of the soil. We have a system of soil here driven by climate and parent material in the scope of this landscape.
TIM WHITE: And so those are issues that we'll talk about in much more detail through the rest of this lesson. Thanks, Ashlee.
ASHLEE DERE: You're welcome.
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