Water!
Wind!
Water!
Wind!
Water!
Whoa!
Hi, Bill.
Hi, Webb.
What's going on?
Bill says that water is more powerful than wind, but wind is so much stronger.
No way!
Wind has nothing on water! and water are very powerful.
It sounds like you're both onto some impressive ways the surface of the Earth can change.
Wind and water can both change the shape of the land.
I have an idea.
Let's compare some of the ways wind and water can change the land, and then we can decide which one is stronger.
Well, okay, but how strong can water be anyway?
Strong enough to make one of the coolest places on Earth, water made the Grand Canyon.
That's right.
The Grand Canyon is a gorge, or a very deep place in Arizona.
It's so big and deep, you can see layers of rock going down around 1800 meters.
You could stack six Eiffel Towers on top of each other from the bottom of the canyon and they would just about reach the top.
Wait, wait, wait.
The Grand Canyon is a giant hole in the ground.
What does water have to do with that?
Water dug that giant hole in the ground, Webb.
About five or six million years ago, two rivers flowed together to create the Colorado River.
But how does a river make a canyon?
Water is strong when there's a lot of it, and the Colorado River has a lot of water, especially when it floods with rain or snow from up in the mountains.
When the floodwaters come through, rocks get knocked into the river, scraping away at the other rocks underwater, making the river deeper and wider.
This is called downcutting, when the rocks moving down cut into the riverbed.
Even when it isn't flooding, there's erosion when the river water carries tiny pieces of the ground away downstream.
The river water erodes the land around it, cutting away bits of earth and rock bit by bit, until there's a grand canyon.
Wait, I'm in water all the time, and I don't get eroded.
Erosion takes a long time.
The Colorado River took millions of years to erode the Grand Canyon and it's still doing it, just a little bit at a time.
That's absolutely right.
Water can take a very long time to change the shape of the land, but it does it in a big way.
We've seen how strong water can be, but let's talk about wind.
All right, my turn.
Let me show you a place that has been shaped by wind.
This is the Namib Sand Sea in Namibia, part of the oldest desert on Earth.
It's home to some of the world's tallest sand dunes.
Dunes are huge piles of sand built by wind, usually found on a beach or desert.
Wait.
How does wind build anything?
It doesn't have hands and no shovels.
Sand is made of tiny pieces of rock, and those pieces are small enough for wind to carry.
When a strong wind blows over sand, it picks up pieces and carries them away.
The wind drops the bigger pieces of sand first.
Those pieces can be...
So when the wind brings more sand, more pieces will stick to them.
That's how a dune starts to grow.
And sometimes it can grow and grow and grow.
Wow.
That one's as big as a mountain.
Yeah.
Some of the dunes in the Namib Sand Sea are over 300 meters tall.
That's about a thousand feet.
That's about one Eiffel Tower tall.
The dunes were built by wind for over a million years and they're still shifting with the wind today.
See?
That's why I think wind is stronger.
I still think it's water.
Both take a long time to create giant landforms or shapes in the land, like dunes or the Grand Canyon.
Actually, I know something that might settle this.
Have you heard of stone arches?
Not yet.
Are they made by water or wind?
Both.
Natural stone.
Arches are formed when water seeps into special types of stone, then freezes into ice and cracks the stone.
Over millions of years.
The cracks continue until the rock is very thin.
Then Wind and water both work together to erode the rock, taking away lots of little pieces around the hole until what's left is an arch shape.
There are famous stone arches all over the world, like Landscape Arch in Utah's Arches National Park or the Shinrin Ferry Bridge in China.
So you're saying that water and wind can work together?
Yep, just like how you two do amazing things when you work together.
That's true.
Bill, thanks for helping me learn about water erosion.
No problem.
Thanks for helping me learn about wind building sand dunes.
Let's go learn more about arches.
Looks like Bill and Webb are going to have fun learning more about amazing landforms and the forces that shape them.
If you'd like to join us, hit the subscribe button below and we'll see you next time here at the fort.
