Soil Layers Part 2

Hi, I'm Jared. Welcome to Fun Science Demos. Today we are going to start by digging in the sandbox. Lots of kids enjoy digging in a sandbox, but unfortunately you can only dig so deep. So today we thought we would get out of the sandbox and try digging in the soil and going a lot deeper to see if we can take a closer look at the different layers in our soil. So behind me, you can see we have a pretty deep hole. But before we take a look at that deep hole and the different layers of soil that we see, I want to take a closer look of our model of all the different layers that we are going to hopefully find in our soil. Our bottom layer is bedrock. That's the rocks and the crushed rocks that's underneath the soil, underneath the ground. So to be our bedrock, we are going to use some vanilla wafers that we are going to drop in whole and some sandy cookies. And we want to just create a layer on the bottom of bedrock. A lot of times when architects try to build things like bridges, they have to dig deep, deep down until they hit the bedrock so that bridge or building won't sink. So I think we have a good layer of bedrock. Crush this one up a little bit. There is our bedrock layer. Rocks from the bedrock look an awful lot like some of the rocks we found back there. The next layer we have to make is our subsoil. And the subsoil is made up from a lot of the rocks from the bedrock broken up into smaller pieces and even a lot of the soil from the topsoil coming down. So to do that, we are going to use chocolate chunk cookies. We do want chunks of rock and some graham crackers to give us a nice finer texture. Put them in the bag. Start with the cookies in the bag. And we are using the baggie to contain everything as we break them up. Now I am using my fingers, but different processes is what pulverizes the rock in the ground. It could be pressure from all the ground pushing down. It could be freezing and thawing. It could be water pulverizing the rock. Now let's add some graham crackers. Snap them in half. Into the bag they go. Close the bag. It's time to crush. So we have our subsoil. We are ready to pour it in our container. Now we have our subsoil. Now we are ready for our topsoil layer. And for our topsoil layer, we are going to need to use a chocolate cookie because the topsoil is actually a different color. It's rich and it's dark from all the nutrients of living things that have broken down. Things like bacteria and fungus break down those living things as they fall to the ground like leaves and plants. As they die, they get broken down and all that nutrient-rich soil is our topsoil layer. So let's drop our chocolate cookies in the bag and crush those up. Now we are ready to dump in our topsoil. Now there are lots of living things in our topsoil. Things like earthworms and bacteria and fungus and insects are breaking down all those dead and decaying things, recycling them back into the soil, putting all their nutrients back into the soil where plants can get all that nutrients back out of the soil. That's why plants have their roots in the topsoil. So we are going to stick some gummy worms in our topsoil to kind of represent those living things in our topsoil. Now our last layer is a layer at the very top called the humus. For that, we are going to use coconut that I put some green food coloring in to give it a nice green color. Sprinkle it on top and we have our humus layer. Now in our models, you can clearly see the layers of soil. We have our bedrock, our subsoil, our topsoil, and our humus at the very top. When we get into our hole, those layers are not going to be so clear, but they are there and we are going to take a closer look at the real soil right now. So I am standing in the hole we dug and it is about six feet deep just so we can get a better look at the different layers of soil. And the first thing you are going to notice is that these layers in this soil are not as clearly defined as our model. You are not going to see a clean straight line between the topsoil and the subsoil and the humus. Let's see if we can take a closer look and see if we can begin to figure out what layers of soil we are looking at right here. The first thing we need to do to figure out what layers of soil we are looking at is let's take a closer look at these stringy things. What are they? These are plant roots and the plants send their roots into the topsoil to get nutrients from the soil and to get water from the soil and also to anchor themselves so they do not just fall over. And you can see our roots extending down into our topsoil. So our topsoil is really a section of soil about the span of my hand up at the top. And at the very top would be our decaying humus. And then underneath our topsoil where the roots start to to stop from growing down is our topsoil. Now below our topsoil we are going to start to get into our subsoil. And a big clue about the subsoil is we start to run into some rocks. And right here you can see I have a bunch of rocks and that is a good sign that I am getting into my subsoil. Now as we go down deeper and deeper we are going to run into more rocks. Where do those rocks come from? Those rocks come from the bedrock. That solid rock and those rock pieces down at the bottom layer of soil. And so we have topsoil working its way down and rocks from the bedrock working its way up. And that is where the different layers of soil come from. Now one thing to remember is that we are in Pennsylvania. And in Pennsylvania we have a nice thick layer of topsoil. But it is not like that in all places of the world. In different parts of the world those soil layers are different thicknesses. Some places might have a very thin layer of topsoil. Some places might have a very thick layer of topsoil. It depends where you are. Remember that soil is a mixture of living things and non-living things. Here we have zoomed in on a layer of our topsoil and you should be able to see tiny little ants scurrying around. Those ants live in the topsoil. Lots of insects live in the topsoil. As you can see digging in the soil it is a dirty job. So why would we go through all the effort and energy to dig a hole to take a closer look at those soil layers? Well because the soil is so important. It is so important for all these living plants you see behind me. These plants get the nutrients they need to live, to thrive, to be in that perfect habitat. It is all because of the soil under the ground that you do not see. If you want to learn more about living things or habitats please check out our channel. Science is so cool and sometimes you just have to stop and try and wonder why. Thanks for watching.