Welcome everyone. We are going to jump back to Chapter 1 in this video lecture to focus on Learning Objective 8, the ROC Cycle. So in Exam 1, we focused on Learning Objective 1 and 7. For Exam 2, we're going to throw in just a dash of Chapter 1. on the rock cycle, because by now we have learned about minerals and we know that minerals are the building blocks of our rocks.
So it is important to understand how those minerals can come together to form our rocks that are so abundant on earth's surface. Again, minerals are the building blocks of rocks. Rocks are formed by the combination of one or more mineral, and they undergo some formation process. And we will see that that formation process is how we group together our rocks.
So there will be three types of formation processes that we will look at this semester. We're just going to introduce them today with the promise that more is to come. The rock cycle is simply a series of processes at Earth's surface or in Earth's interior that can cause rocks to form, change our rocks, destroy our rocks, reform our rocks, and so on. Every rock on Earth is at a stage along this rock cycle. We're going to show exactly how we can work through that cycle and the numerous paths.
that are present on this rock cycle. But before we do that, I just like to introduce the three rock types. This again is going to be a short lecture, so we're not going to get into these rock types any more than this slide, really, because in chapters four, six, and seven, we'll really do a deep dive into these individual rock types.
The first we have igneous rocks. These are going to be formed from volcanic processes or volcanism. So volcanism is the process of magma trying to rise to the surface and erupt as lava, big volcanic eruptions.
And when that molten material cools down, it can form igneous rocks. So that's its formation process. Next up are sedimentary rocks.
I like to call these mother nature's leftovers. These sedimentary rocks can form from whatever's available. Just like when you have leftovers, it's whatever's in your fridge. Sedimentary rocks will form from whatever's nearby. And that can include not only preexisting minerals or preexisting rocks, but in some extreme cases, things like plant or animal remains.
Very interesting because we learned in chapter three that minerals by definition must be inorganic. There are some special cases in sedimentary rocks where these materials will form from plant or things like shells. Plants or shells really are what we'll focus on.
But that stuff existed. It somehow became cemented or combined together to create a sedimentary rock. The final rock type that we will talk about, metamorphic rocks. Metamorphosis means change.
We will see across Earth's surface, there are a number of processes that can change our rocks. This also happens in Earth's interior as well. And when our rocks change from one type to another, they undergo a metamorphosis, creating these new rocks. So these are formed by changes.
In this example, marble, beautiful milky stone often used for construction, used in art, is an example of a metamorphic rock. So now we're actually going to work through the rock cycle together. There is a copy of this. assignment on Canvas. It is not graded.
You do not need to submit it to me. There's no bonus points for it because I'm going to go through it with you here. but if it helps you kind of study and make sure you understand the rock cycle, I wanted to make it available for you. So on the left, we have our word bank.
We have our three rock types dictating the type of formation process. And then we have a list of processes that can affect our rocks. They can help rocks form.
They can help them break down, become destroyed, change. There's a lot of different processes happening here. And as we move through the upcoming chapters, we'll get very specific on things like weathering, uplift, heat, pressure, crystallization, and so on.
So the first thing we want to do is fill in our first blank to kind of figure out where the rock cycle may start. You can start anywhere. on this rock cycle. I know that it is lettered from A to I.
I didn't do that because I don't really think we should start at A. I want to start at the bottom. I want to start with magma. That's where I want to start because magma, specific process, magma wants to rise up to the surface through processes of volcanism. And we learned that igneous rocks are formed by volcanic processes.
So we know that magma must undergo some change, G, to form an igneous rock. So I can feel confident that even though we don't have the letter G yet, that magma, we see this arrow here, forms igneous rocks. So I'm going to cross off igneous rocks.
I want to see how magma can form an igneous rock though. So let's go over to our processes, this kind of second chunk of words. Weathering and erosion.
Weathering and erosion happens on the surface. Weathering is the breakdown of material. If you leave your bike outside or your patio furniture, right, you've probably seen the paint start to peel, maybe some rust.
Erosion is the transport away of that stuff. That doesn't sound like what's happening with igneous rocks. Tectonic uplift is the pushing of rocks to the surface, not rising due to magma or volcanic processes, but literally just plates shifting and pushing rocks up. Eh, maybe, but we'll come back to it. Heat and pressure.
We think back to our previous slide, we know that heat and pressure is tied mostly to metamorphic rocks. So I think we're going to count that out. We have crystallization, which is taking something molten, cooling it down and forming something solid.
We have magma. It is hot. It is molten.
And as it cools, it will crystallize. So I think I have. found the letter G here with crystallization. Blocks are a little big for my, got big handwriting.
So crystallization, I'll put the letters next to it. Awesome. So we have our igneous rocks.
Magma forms igneous rocks, crystallization deep in earth's interior. We'll learn the distinction between magma and lava in chapter four. Just take my word for it now.
Magma is deep, deep, deep down. But if we look at letter A, we're going to jump ahead a little bit. We see that we are back on the surface of our planet, right?
So igneous rocks here, we're going to say are in Earth's interior for this example. We need to get from the interior to the surface, letter A. So to get from H to A, this arrow, we need to somehow get the material from deep underground to the surface.
Well, I mentioned this or defined this already. Tectonic uplift, pushing material up. So tectonic uplift it is for letter I.
Terrific. So we're now on the surface. What happens on the surface? Well, rocks are subjected to a lot of different stuff. They're going to break down as it rains, as it snows, as wind picks up particles.
If you're in a desert, for example, it's like being hit with sandpaper. The sand grains in the desert will just grind you down. We call this weathering and erosion.
Weathering is the breakdown of material. Erosion is the transport of that material away. And it happens at the surface due to things like weather.
You can see in this image, there's some rain. So weathering and erosion will be letter A. As weathering and erosion continues over thousands of years, it can take that igneous rock and essentially break it down into tiny pieces. We call that sediment.
So we have sediment here. We see if we follow the arrows, we have those sediments. Sediments are pre-existing particles that somehow will become sedimentary rocks. So we're going to jump ahead. We're going to skip letter B.
We know that the sediments must become sedimentary rocks. I haven't described how yet. But we know that our sedimentary rocks must be there.
So let's look at our processes that are left over. There's only three left. We have heat, pressure, burial and lithification or melting.
So let's think about loose sediment, loose sand in the backyard, loose mud. Heat and pressure doesn't really seem like it will help it solidify. Maybe the pressure part, but heat.
Not so much. The same with melting. We don't melt our sediments to get at sedimentary rocks, but if we bury them, pressure it, putting them under pressure and then lithify these rocks, which means cement them together, give them compaction, that loose sediment can become a sedimentary rock.
So burial and lithification. are how sediments become sedimentary rocks. Boom.
We only have a few key terms left. We have D, E, and F. Well, we know that E is associated with our rock types, right? We have our three rock types here.
We only have one rock type left. So we know that it must be metamorphic rocks. So how do we go from sedimentary rocks to metamorphic rocks. They have to undergo some changes. That's what metamorphism means.
And we know that heat and pressure are what cause metamorphism to occur. So letter D, B, heat and pressure. We are going to heat up and pressurize our sedimentary rocks, changing them from one type to another.
I gave the example of marble as a metamorphic rock on the previous slide. Marble is formed when we have chemical activity changing a sedimentary rock. You can also have heat and pressure applied as well.
So that leaves one term left, melting. Let's make sure it fits before we just kind of put it in there willy-nilly. We have our metamorphic rocks and we see this final arrow leads to magma. So we're going from a solid material to a molten hot. material.
Yeah, melting sounds about right. So we'll pop melting in that, oops, excuse me, in that word bank, giving us one possible way to proceed around the rock cycle. Now there are a number of other arrows here.
For example, igneous rocks can undergo heat and pressure and become metamorphics. Sedimentary rocks can become uplifted, eroded. re-con, uh, reform or re-cement into new sedimentary rocks. There's a million different ways to cook an egg.
There's a million different ways to go around this rock cycle. This is just one process that we worked through. The reason I like to go through this is because it shows that all of the rock types are connected.
And when we look at our rock cycle, like you see here, another simplified version. What this tells us is that any rock type can be derived from any rock type, meaning even the same rock type. So.
igneous rocks can form from other igneous materials. If it's melted, right? Igneous material melts into magma that cools into igneous rocks.
You can kind of have that feedback loop. Igneous rocks can form from metamorphic rocks. Again, if metamorphic rocks melt and then cool, we get igneous rocks again. Igneous rocks can even form from sedimentary rocks that are melted down.
giving us igneous. So the same is true for metamorphic and sedimentary rocks. They can be formed from any other rock type, including themselves. So each rock type can be formed from the three existing types. Excuse me.
So that is our rock cycle. That is the end of this lecture. It's fairly short, but it gives us some insight into how these three rock types will differ from each other.
and how their formation processes take place. So again, we will focus on igneous in chapter four and chapter five. Sedimentary rocks will be chapter six, and then metamorphic rocks will be chapter seven.
So we can look forward to getting really familiar with these three rock types over the next few video lectures. Next up is the chapter four. material.
So when you feel good about this rock cycle, maybe you work through the diagram yourself, come on by and see me in the chapter four video lecture. So we can begin our discussion on igneous materials.