Earth Science: Exploring River Formation Lab

Here is a lab I created for my High School Earth Science course using old salad bars as stream tables to model river formation, stream abandonment, and ocean sediment layering.  The lab went well. i was a little worried that students would think this was too elementary, but most of them enjoyed the lab and watching water trickle through sand sediment creating rivers and banks.  My goal with this lab was to have them understand a little about why the world's rivers are shaped the way they are.

Grade Level: Can be modified for all grades, but designed for Jr. High and High School Earth Science

Materials Needed:

  • Stream tables, sand, ruler, water jugs (or any means of slowly trickling water into your stream table), a bucket to catch excess water.

Procedure:

  1. Pass out the student Exploring River Formation Lab sheet.

  2. Select a couple of students to manage the flow of water.

    • I had two stream tables that were nothing but used salad bars that were discarded in the districts junk pile.  I could believe how awesome that was.  I am hoping over time to get a few more.  Salad bars are perfect stream tables because they are on wheels and have an area that will drain water.

    • River Formation Lab

  3. Once the water is flowing, stand back and let students discuss the lab questions together.  I facilitated this conversation.

Expected answers and discussion from the lab sheet:

1. What are some observations that you can make right way about the flow of water?

  • Looking for discussion about how the water is choosing the path that it is.

2. Describe how the sediments are moving.  Sand vs. silt.  

  • Students should recognize that the smaller grained particles are moving quicker down slope and the larger particles are comparatively slower.  I had my student imagine the sand sized particles as being larger particles in a real river.

3. Describe how the path is being formed down hill.

  • After about 5 minutes the “river” should be forming a path to the “ocean basin” below.  If they are paying attention closely they will notice that the path shifts as it take the easiest way down.  Over a few minutes the river should start to change direction again as it piles sediments up forcing the river to change.

I now have the student use the rulers or their hands and add a “landslide” to the river.  Rivers have been know to change their paths due to natural blockage such as landslides or lava flows.

4. What do you notice about the water’s “chosen” path?

  • Now they really see how the river will have to change direction due to the blockage.

5. Why do you think it took that path?

  • They should be thinking about the path of least resistance as water will find the easiest way to drain to the basin.  Once the river breaks through the barrier if flow very quickly.  I tied this into historical examples where natural dams and barriers in a river's path created devastating damage downstream when the dam broke.

Now I have the students smooth the slope with the ruler again.  This time they should create large broad loops, or meanders in the river and start allowing water to flow again.

Meanders in Rivers Lab

6. Describe how the erosion is now affecting your stream.  

  • How is it eroding the sides?

    • They should notice and if they don’t get some guidance the teacher, that the river goes quickly to the outside of the bank and is moving sediment slightly slower on the inside of the bank.

  • Are the sides getting wider?

    • They should notice after about 5 minutes the the sides of the river are getting wider and the depth of the river is getting shallower as the sediment piles up.

  • Which side of a bend or a meander is being eroded fastest? and Why do you think it is being eroded the fasted?

    • They should see that the river’s outside bank is changing the quickest due to the differential speed of the water as it hits the outside bank quicker.

  • Which side of a bend is having the most deposition occur? and Which types of sediments are mostly being deposited? Sand or clay?

    • Students should notice that the inside bank is where the deposition occurs the most.  This wasn’t so obvious when I do the lab so I have to point it out which sparks discussion about why that is.

Now the students take a look at the sediment in and around the river’s mouth and the ocean basin.

Sediments in Ocean Basins lab

7. What type of sediment is found at the edge of the “beach?” Sand or clay?

  • They should notice that the further you go into the ocean the more clay and silt sized particles will be found.

8. Why do you think that is?

  • This happens because the heavier sediments such as the sand drop out of the water first as the lighter material can float further into the ocean.

Lab Extension

  • One of the lab extensions I tried at the end of the day was to mark with a pencil the location of the furthest part of the “beach” in the ocean.  Then I had students take note that the mouth of the river actually moved enough sediment into the ocean that we created our own little delta.
  • I also showed students this video at the end of the lab.
  • Why Do Rivers Curve?