The Grand Canyon is one of the wonders of the world, but have you or your kids ever wondered how it got there? Did a massive system of channels just appear in the ground one day? Of course not, The Grand Canyon was created by millions of years of erosion, but it’s hard for us to visualize what that looks like. To help us visualize, let’s create an experiment in which we see erosion on a much, much quicker scale!



Supplies:

Various items we'll use to perform our erosion experiment
  • A disposable cup
  • A straw
  • Playdough or clay (something to seal our hole)
  • A utility knife
  • A large jug of water (if you’re doing this outside, you can use a garden hose on a very slight trickle
  • A cookie sheet, or something flat with a slight edge
  • Sand or soil (I’m using play sand that I got from the hardware store)
  • 3-5 2x4s or bricks (something to vary the slope of our sand)

Step 1: Make Our “Earth”

A cookie sheet filled to the edges with sand

Let’s make our earth first!  This will represent what The Grand Canyon was like before the Colorado River started eroding it. 

Fill the cookie sheet to near the top of the sides with sand. Smooth the top as much as possible.

Step 2: Make Our “River”

Take your disposable cup and gently cut a hole in the bottom of it using a utility knife. I cut a small X with the knife rather than an actual circle.

Insert your straw in the hole.

Seal the edges of the hole with clay or playdough. You’ll likely still have some leakage when you add water, but the vast majority of your water will come out our straw “river”.

Step 3: Set The Grand Canyon Scene

A cookie sheet filled to the edges with sand

Lay your earth out. We’ll start with our earth flat and we’ll see what happens, then we’ll try again with a couple different slopes.

Set the river on the edge of the earth and pour some water in the cup.  That water is going to represent the Colorado River, which is the river that formed the Grand Canyon. 

What’s it doing?  Just kind of pooling there, right?  It’s not moving very much and it’s not taking much earth with it.  

Water pooling under a straw

Step 4: Change The Slope A Bit

Hands inserting a 2x4 block to increase the slope

Let’s try with a different slope. 

Put a piece of wood under one end of the earth.  See how we changed slope?  Now our earth is like a little hill.  

Set the river on the end of the earth just like last time and pour water through it. 

What’s happening now?  How is this different than when we had no slope?  We’re getting more movement, right?  And as the water moves, it’s taking sand with it, causing erosion.  Note how sand collects down at the bottom?  That is earth from the top of the hill moving downward. 

Water and Sand moving downhill

Step 5: Create A Mountain Slope

A cookie sheet filled with sand at a steep angle

Let’s see what happens as we increase the slope from a hill to a mountain!

Add another piece of wood under our earth and repeat the experiment again, running our river through the sand.

And look at that!  We’ve collected more sand at the bottom than we did in either of the other two experiments. I think that’s pretty good evidence that the steeper the slope, the faster erosion occurs. And if you watch the video, you can see that erosion took all the soft sand downhill, leaving us with just the hard, erosion resistant layer at the bottom. In this trial, the water really does create a mini canyon!

A sheet filed with sand.  Water is carving a canyon down the center of the sand.

Extensions And Ways To Use This As A Science Fair Project:

If you’re looking for a fairly simple science fair project, you could easily convert this experiment into one. Perform the experiment like we did above with the three different slopes, taking pictures as you go. And to collect data, put a container at the bottom of the slope to collect the water and soil/sand as it moves downhill. Measure the amount of water and soil from each experiment and that should provide some conclusive data.

Another experiment you could do would be to see how ground cover affects the amount of erosion. Do the experiment twice with the same slope. Either the “hill” or the “mountain” would provide the best results. On the first trial, do it as we did the trials above, no ground cover at all, just soil. Next time, cover the soil with a bit of ground cover. Something like thin cotton batting might be a good example. Then run the experiment again. Measure the water and soil that moved downhill each time.


Wasn’t it cool to watch erosion occur right in front of us? It makes it so much easier to see how magnificent canyons like The Grand Canyon were formed.

If you’re looking for more simple science experiments to do with kids, make sure to subscribe to my YouTube and check back frequently, I post crafts and experiments weekly!