Video
Springs of Zion
Transcript
Hello, my name is Cheyenne, and I would like to talk about an amazing geological process that happens here in Zion National Park. Do you see that? That's a spring behind me releasing water. Notice how the water is flowing down the rocks and how the mosses and ferns are growing from it. Water flows almost everywhere here in Zion. Have you ever heard of or been to the Narrows of Zion Canyon? It is a deeply carved canyon with vertical sandstone walls that took millions of years to form. And, did you know that water is a powerful force that still continues to carve the canyon today? The Virgin River and its tributaries carry away around one ton of material every year from this canyon. Water is the main reason why Zion looks the way it does today. You'd be surprised at the places that you can find water in the desert. Did you know that there are canyon carving elements hidden within these rocks behind me? Zion springs showcase the hidden history of canyon carving concealed within its sandstone walls. Before we jump into how springs are made, we need to have an understanding of the geology here. Geology is the study of the earth and especially rock formations. Behind me, you can see some of Zion's large red cliffs. The rocks here in Zion National Park are millions of years old, and all of them are layered like a tall layered cake. Each of these layers has something unique about it. These sheer white and pink cliffs towering behind me make up the Navajo sandstone layer. This type of rock is called sedimentary rock. Sedimentary rocks are made up of small pieces of rock, or sediment, that were deposited here and then lithified, or hardened, into a new rock. Now, what do you think sandstone is made out of? Yeah, sand! The shape of the sand here is super round, and this shape allows for air and water to move around them in the cliffs. Now, let's take a look at the top portion of this image showing the roundness of the sand in the Navajo sandstone. As you can see, there are tons of gaps between the sediment. I like to imagine this kind of like a ball pit. There are tons of spaces between the balls which allow you to walk through it easier. We actually have a word for this, and it's called being permeable. A material that is permeable allows water to move through it. Water can easily move through sandstone, and that makes it very permeable. The Navajo sandstone layer might be permeable, but the layer underneath it is not. This layer is called the Kayenta layer, and it is another sedimentary rock called siltstone. You can see it behind me as a hilly formation beneath the Navajo sandstone. Let's take a look at this picture that I've shown previously. On this bottom portion, you can see the Kayenta siltstone. Siltstone pieces lay flat and snugly next to each other, and this creates less pockets for water to travel through. Kayenta siltstone is not permeable. Instead, the water will travel across the top of it instead of through it. Let's demonstrate the permeability of these two layers with this water bottle. The bottom of this bottle is filled with children's clay acting like the Kayenta siltstone, and the rest of the bottle is filled with round marbles acting like the Navajo sandstone. Let's pretend it's raining in the canyon. So, I'm going to pour some water in the top of this bottle. Look at that! The water travels right through the Navajo sandstone, but it doesn't go through the Kayenta siltstone. The water will sit between these layers and travel downhill until it reaches a crack in the side of the cliff face, and this creates a spring! A spring is where water flows out of a cliff face or a crack in the rock. We have many springs in Zion Canyon like the one I'm standing in front of now. This water can take thousands of years to travel through our sandstone cliffs. All of this water flowing through the Navajo sandstone and along the top of the Kayenta siltstone carves the rocks from the inside out. As the water is moving through these layers, it picks up small pieces of sand and silt and carries them out of the rock. As these pieces are getting moved out, they rub up on the walls of the rock, kind of like sandpaper, and carry out more sediment with them. This is called erosion. There's another way that water can change our canyon walls. During the winter months, temperatures can drop below freezing. This causes the water in our sandstone cliffs to freeze within the cracks. Think about if you've ever put a water bottle in the freezer before. Water expands when it freezes, and you might have even seen that water bottle crack open or explode. The same thing happens with our rocks here. The water will freeze within the cracks, pushing them wider and wider, until the rocks can't hold on anymore. This causes huge rock falls, and these rock falls contribute largely to the widening of our canyon. The unique geology of Zion allows springs to form which contribute to canyon carving with erosion and freezing methods. Without the hidden workings of water, the canyon wouldn't look the way it does today. If you're planning on coming to Zion National Park anytime soon, I recommend taking a stroll down the Riverside Walk and looking for some springs and hanging gardens there, and while you're on our shuttle, keep an eye out for previous rock falls we've had at Weeping Rock.
Description
Ranger Cheyenne investigates the amazing geological processes of Zion National Park, and shows how the rock layers at Zion help create beautiful springs and seeps in the canyon. This program is designed for upper elementary-aged students, but can be enjoyed by all!
Duration
5 minutes, 44 seconds
Credit
NPS
Date Created
08/24/2020
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