Tuesday, November 19, 2013

Erosion, Sediments, and Fossils

My morning began with setting up dirt.  This did not go as easily as planned because it didn't think it had been cold long enough for the ground to be frozen.  WRONG!  Fortunately it was only frozen for a few inches.  A metal spade did the trick.  Also fortunate was the cooperative weather.  It was cold, but we didn't have straight-line winds or tornados circling above us today.

Kal-El has been asking to learn more about fossils.  To that end we began section D-8 of Building Foundations of Scientific Understanding (K-2).  Some of this work is very similar to what is in the Montessori Elementary Geography album at the beginning of the section "The Work of Water."  However, the Montessori demonstration provides a bigger picture.  We will do that work later.  For now, we wanted a straighter path to fossils.  

So, we started with some fossils.  I grabbed a few that my husband collected as a child.  I have a nice set of fossils from Montessori services as well.  I'll pull those out later.  For today, I didn't want the fossils to take us down a historical path focusing on what the living creatures used to be. I also didn't want to worry about all the fossils being separated from their labels on the first day either.  Starting with some striking but unspecific, unlabeled fossils was perfect.

I love how the BFSU scripts have you open with questions rather than start lecturing.  I asked, "What are these?"  Kal-El shouted out that they were fossils right away.  "What are fossils?" The boys examined the fossils and determined that they are rocks that look like, or were, once-living things.  

The next questions was, "How did they get there imbedded in the rock?  What do they tell us about the history of the Earth? Let's investigate this."

So that brings us back to my loamy soil.  I put a 2-3 quarts on top of my one and only dish drainer from my actual kitchen.  This is set up to (hopefully) drain into a clear gallon or couple-gallon container of some sort, in this case my favorite lemonade pitcher (this is what dishwashers are for I guess).  I also have a large watering can filled with warm water (to help me out with the slightly frozen soil).

Believe it or not, I was unable to take a photo of myself while I carefully made it rain by sprinkling the soil with the watering can.  As you can see, not all of the water and dirt made it into my favorite lemonade pitcher and Kal-El's face tells you plainly that he knows this was ALL MY FAULT.  Me Too is looking on with silent horror.  It wasn't that bad. MOST of the water and dirt landed exactly where intended.  The adult needs to sprinkle the water because it needs to be done at just the right rate so that the kids can see the smallest particles (clay) quickly carried away by the water, the mid-sized particles (sand) carried away more slowly, and the rocks and pebbles stubbornly staying put.

We learned the words erode, erosion, and sediment. This work led straight back to the First Great Lesson because we observed that the particles were separating according to size and density.  We talked about why the water in my sprinkling can was clean and yet the water in the lemonade pitcher was dirty. Then we recalled looking at the local creeks and rivers after heavy rains and the boys recognized that the water was full of sediment in that case as well.

Next we recalled that streams and rivers empty into lakes and eventually into the ocean. Here again we reflected on the First Great Lesson in which we learned that substances settle according to weight.  We observed the particles settling in the lemonade pitcher and could see the same behavior.  Bringing it back to fossils, we wondered about what would happen if fish, shellfish, seaweed, etc., are buried under this incoming sediment.  We talked about what parts of the living things would rot and what would remain behind.  

The next questions was, "How do the fossils end up in rock rather than in just loos sediment?"  We talked about how the pressure created by increasing layers of sediment piling on top together with chemical factors creates sedimentary rock.

The next question was, "Is there just one kind of sedimentary rock?"  I pulled out one of our rock collections and took out specifically the sandstone and the shale.

The boys examined them with magnifying glasses and the microscope.  The sandstone is made from sand and the shale from clay.  The BFSU script has you point out here that we find shale and sandstone separately.  The traditional Montessori presentation for layers of sediment focuses on the idea of layers and different materials settling over the ages.  The BSFU mentions that the particles could have settled out at different times, but focuses on the other option:  That they can also settle at the same time but in different locations. "We just observed [in the dirt/sprinkling can demonstration] that different sizes of sediment particles were separated as they were carried along by the water...As the water slows and stills, larger particles, namely sad, settle quickly near the mouth of the river, smaller particles (clay), which take longer to settle are carried and settle further  from the river's mouth" (BSFU, lesson D8).

I demonstrated this effect by putting a handful of our dirt in a jar which I shook to separate the dirt particles.  We observed the jar and saw the larger particles (rocks and pebbles) fall immediately to the bottom.  Within a few minutes we also had a layer of mid-sized particles.  The rest of the water was still cloudy with clay particles.  We'll give it a final look tomorrow, but as of this afternoon the water is mostly clear and we have a new layer of fine particles on top of the earlier sediment.

Also discussed was a miriad of topics such as why we can find fossils in any kind of sedimentary rock but never in igneous rock (Kal-El thought the very notion was hilarious), why we have grass on our front lawn, why Dad should really put mulch on the dirt around the patio, why it is bad if we get too much rain too quickly (I may have gotten overzealous with the watering can a few times), and where WOULD all the dirt from our yard wind up if we didn't have grass or trees.  Right now the boys are outside scouting for the neighborhood's "low spot."

If you are familiar with the traditional Montessori presentations for "The Work of Water" you can probably easily see how this work could be combined with that and/or easily extracted from that larger work.  The BSFU continues on with a whole section on limestone at this point. We decided this was a good stopping point and will be continuing that work tomorrow.


  1. I was laughing out loud about that picture and your description! So funny! Looks like a fun lesson.

  2. I'm absolutely loving the details and complexity you're exploring with your boys. Fascinating presentations!

  3. Hi! This is a super post and right on point for the theme of this week's Carnival of Homeschooling, so I linked to it. You can find the Homeschool Carnival at http://petticoatgovernment.blogspot.com/2014/09/carnival-of-homeschooling-456.html.