Thursday, September 30, 2010

Adapting the stream table lab (Investigation 2B: Modeling a River)

CPO Earth Science labs are called Investigations---or "student record sheets" in the right column on this page .  Open the document for Unit 1 and find Investigation 2B if you'd like to follow along.

As much as I would like to own a fancy, schmancy dedicated stream table, it was time to be realistic and adapt somewhat household supplies to do the same job.

I started with a $1.87 white plastic deep paint tray liner from a Big Box Hardware Store.  Dh cut a hole in the deeper end and inserted a plastic spigot.  The spigot came from a foodgrade bucket he uses for homebrewing, but one can purchase individual spigots at the BBHS (or a homebrewing shop, if one is so inclined).

The plastic was quite thin, so I backed it with four or so plastic lids from Costco party trays (I knew I was holding onto them for a reason!), tapped securely down with packing tape.   Here's a side view of the high tech set-up :
When the "stream table" was placed on the folding chair, it needed to be angled just a smidge more, so I placed the lid to a small cooler under the non-spigot-ed end.  The upper bucket is another foodgrade brewing bucket with a plastic spigot and the lower bucket is just a regular one.  It was there to catch water overflow from the stream table, as needed.  We used just regular play sand and tap water.
The first step was to observe what happened when the water entered the stream table system.  Apparently the tray wasn't perfectly level, because the neophyte stream headed to the right almost immediately.  Daisy was thrilled to discover that two channels developed, creating a sandbar in between.
She chose the vary the postition of the entering water for the remainder of the experiment (she could have chosen another variable such as the amount of sand in the tray, the angle of the tray, etc).  Starting from the right, you will notice that another mini sandbar developed:
(We had to use a regular kitchen funnel to guide the water from the upper bucket.  It was really windy and the stream of water was blowing around too much.)  From the center postion, you can see the pronounced lean of the "stream table" but hey, it's all cool and geeky:
And lastly, from the left position.
After all observations were recorded and her hypothesis (The path of the water will change direction when the postition of the entering water is changed.) was checked to see if it was correct (yep), it was time for some Stream Table Fun.  Note the interesting river system she created before flooding it all out:

Try it at home!

Coming up as soon as I can upload the pictures-----Investigation 3A: Convection in Earth's Atmosphere  and my adapted GeoBox!

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