Get ready to be swept away with knowledge, like a particle of sand being eroded through a stream! Today we are going to study weathering, erosion, and deposition. Then we are going to take a look at how eroded particles and other factors can influence the health of a stream. We're even going to build our own erosion models. Let's dive in!

Weathering and Weather: 

Other forces that can cause erosion

We've determined that "weathering" refers to the breakdown of rocks and minerals on the surface of the Earth, but so far we've mainly focused on how water, in the form of rivers or rain, can be responsible for this process. There are numerous other forces that can contribute these processes, including wind and other forms of weather. There are also other contributors like plant growth and exposure to chemicals. These forces can be divided into two categories: mechanical and chemical. 

• Mechanical weathering - The breakdown of rocks, minerals, and soil by physical processes. In this situation, the rocks break into smaller pieces, but the chemical composition of the rocks does not change.

• Chemical weathering - Decomposition of rocks, minerals, and soil through chemical processes. Chemical weathering changes the composition of the rocks, causing the shape or color of the material to be affected.

Look through the slideshow of examples of weathering and erosion below and decide which are examples of mechanical processes and which are chemical:

How do we measure these qualities? 

Let's find out! Check out the video to see how to calculate the velocity of the flowing water and measure its turbidity.

What else can we measure?

When we're analyzing a stream, we want to record data about multiple features so we can figure out how healthy it is. Healthy streams allow lots of organisms to thrive and keep the environment happy. Here are the factors we will evaluate today:

• pH - The measure of how acidic or basic the water is can help determine the health of the stream. A neutral pH (near 7) is best for most organisms.

• Temperature - This measurement varies greatly due to location and time of year. The general rule of thumb is that we want it to be cool enough for organisms to thrive. When it gets too hot, certain creatures struggle and the stream may evaporate faster.

• Biodiversity - A healthy stream will have a variety of organisms in it. We can look for specific critters that thrive in different environments to determine the quality of the water. If we look at the diagram below, we can see that finding sensitive organisms that can only handle ideal conditions means that the stream is healthy. If you have a stream or pond near you, try looking for these creatures! The dichotomous key below the chart could help you identify some of the creatures you might find.

• Turbidity - We measured this earlier. A low turbidity indicates good health.

• Oxygen level - We can estimate the amount of oxygen based on the velocity we measured earlier. When a stream moves quickly, it bubbles over rocks and sticks, absorbing oxygen and allowing organisms to breathe. The flow rate also helps regulate pH and temperature.

The video below will guide you to measure each of these features. Feel free to try it out if you have access to a stream or pond!

A healthy stream indeed.

The results from our measurements indicate that this stream is in good shape.

• Velocity: Our measurement of approximately .71ft/sec in the video is not exactly accurate since the ball stopped in the middle, but we measured several times off camera and found that the velocity was consistently in the vicinity of 1.0 ft/sec, which is a decent flow rate.

• Turbidity: The water was clear enough to see through when the tube was completely full, indicating low turbidity.

• pH: Our data indicates that the pH was pretty neutral, somewhere around six or seven

• Temperature: A healthy temperature can vary based on the weather, time of year, and location. The temperature of 50º F or 10º C is cool enough for creatures in this region.

• Macroinvertebrates: There were plenty of different creatures to suggest that the stream has a diverse population.

The views around these river valleys are great! In fact, they're absolutely gorges.

Outdoor Erosion Challenge

Now that we know what a healthy stream looks like, let's take a minute to think about how we could keep it that way. Cutting down on erosion can improve many aspects of the environment, including the health of streams. In this challenge, you will get to go outside and create your own system for reducing erosion! Watch the video below for inspiration, then read the challenge instructions and get outside!

Your Challenge, Your Choice

Based on what you've learned, you can choose one of the following tasks for your erosion challenge. Complete it, then come back inside for a reflection and a quiz.

In each version of the challenge, you will build two identical landscapes. Then, you will add your own device(s) to reduce erosion, but only to one of the models. Then, you will introduce the force meant to cause erosion. Evaluate the difference between the two models. Did your method of controlling erosion work? See the images below the instructions for ideas of how these models might look.

*Before you begin: Make sure you find a place where you have permission to do this activity. Do not dig up a flower bed or make a mess in someone else's yard!*

A. Glaciers and gravity

1. Place two open containers of water in the freezer to create  blocks of ice. (Do not use a glass container that could break when the water freezes)

2. Build landscapes with soil, gravel, and any small natural objects you find in the backyard. Tilt them so there is one side that is higher than the other in each model.

3. Research ways to cut down on erosion. Create a system that you can apply to one landscape.

4. Place your ice blocks at the highest points in your landscapes. Observe what happens when the glaciers melt and slide across the land. Did your method help control the erosion? Why or why not?

B. Rainy weather weathering

1. Build landscapes with soil, gravel, sand, and any natural objects you want to add. Tilt them so there is one side that is higher than the other in each model.

2. Research ways to cut down on erosion. Create a system that you can apply to one landscape.

3. Fill a watering can or pitcher with water and slowly pour it onto your landscapes, starting at the highest point. 

4. Observe what happens when the rain washes over the land. Did your method help control the erosion? Why or why not?

C. Build your own beach 

1. Place sand in plastic tubs or boxes. Leave one side empty and create a gradual slope up to the other end. 

2. Research ways to cut down on erosion. Create a system that you can apply to one beach.

3. Pour water into the empty side of the bins to create a shoreline. Press down on the water with an object or your hand repeatedly to create waves.

4. Watch what happens to the shore. Did your method help control the erosion? Why or why not?

Review and Reflection

Great job today! We've covered a lot of material, so let's reflect on what we've learned before the information weathers and is eroded away!

1. Forces of weathering and erosion have been changing the appearance of the Earth ever since Earth was formed. How do you think the world will look in 1,000,000 years after erosion has continued to affect the land? What will have changed?

2. The grand canyon was formed through erosion. Can you think of any other landmarks that were made this way? Compare your answers with a friend or family member and see how many you can come up with.

3. When we evaluated the stream, we looked at the macroinvertebrates within it. If the stream health declined and the macros died off, what other parts of the environment would be affected? 

Quick Quiz

We've broken down a very big topic today. How much do you remember? Let's find out with a quick quiz. Feel free to look back at the lesson if you need help. 

About the Author

Rainbow*

There are so many colors of the rainbow, and she likes to use every one! When Rainbow graduated from high school, she went to Kent State University to study fine art, but found that her favorite time of year was the time she spent working at summer camps in between semesters. If you've been to an Ohio Girl Scout camp lately, you've probably seen her there! After earning a BFA in painting and sculpture, she came to Nuhop to work in a camp setting year-round. Her favorite activities are campfires, the high ropes course, and rock climbing.  She can't wait to see the smiling faces of all her campers when they come to Nuhop once again!

*The Nuhop Outdoor Education Staff use "nature names" when working with students. The reason for these nature names is twofold: first it gives them a built-in conversation starter with students, and second, it provides them a level of personal privacy when working with over 4000 students in a given year.