A Skeleton in the Woods

June 22, 2013

Raccoon skeleton and bits of fur found in the woods behind Ms. Eisenberger’s house. Photo by Micaela Mason.

Just out of the blue, I got a text from Maggie (Eisneberger) yesterday saying, “Wanna see something awesome. Bring the kids.” Well I didn’t have the kids with me, but I went over anyway. She and her niece had found an almost complete skeleton in the woods.

Since I’ll be teaching biology next year, I’ve been on the lookout for a good skeleton. The last time I had one was when my middle school class found a raccoon skeleton on an immersion trip. They brought it back to school, cleaned it up, and reassembled it on a poster board. It was an awesome learning experience.

This skeleton is even more complete. Even some of the cartilage between the vertebrae was dried out and preserved. It was a bit puzzling that the whole skeleton seemed to be there, and had not been too disturbed by scavengers even though, based on the state of decay, it had been there for quite a while.

We collected as much as we could, although some of the smaller bones in the hands and feet are quite tiny.

Maggie lent me her book on the animals of Missouri so I could try to identify it based on the teeth. However, later yesterday evening I got an email from her. She’d been talking to her brother, who’d, back in March, shot a raccoon that was going after his chickens. He’d left the body out in the woods.

Well now someone/s will have a nice little project in the fall.

Citing this post: Urbano, L., 2013. A Skeleton in the Woods, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

The Geology of Oil Traps Activity

July 7, 2012

The following are my notes for the exercise that resulted in the Oil Traps and Deltas in the Sandbox post.

Trapping Oil

Crude oil is extracted from layers of sand that can be deep beneath the land surface, but it was not created there. Oil comes from organic material, dead plants and animals, that sink to the bottom of the ocean or large lakes. Since organic material is not very dense, it only reaches the bottom of ocean in calm places where there are not a lot of currents or waves that can mix it back into the water. In these calm places, other very small particles like clay can also settle down.

Figure 1. Formation of sandstone (reservoir) and shale (source bed).

Over time, millions of years, this material gets buried beneath other sediments, compressing it and heating it up. Together the organic material and the clay form a type of sedimentary rock called shale. As the shale gets buried deeper and deeper and it gets hotter and hotter, and the organic matter gets cooked which causes it to release the chemical we know as natural gas (methane) and the mixture of organic chemicals we call crude oil (see the formation of oil and natural gas).

Figure 2. The trapping of oil and natural gas by a fault.

Shale beds tend to be pretty tightly packed, and they slowly release the oil and natural gas into the layers of sediment around them. If these layers are made of sandstone, where there is much more space for fluids to move between the grains of sand, the hydrocarbons will flow along the beds until they are trapped (Figure 2).

In this exercise, we will use the wave tank to simulate the formation of the geologic layers that produce oil.


  • Wave tank
  • Play sand (10x 20kg bags)
  • Colored sand (2 bags)


For your observations, you will sketch what happens to the delta in the tank every time something significant changes.


  1. Fill the upper half of the tank with sand leaving the lower half empty.
  2. Fill the empty part with water until it starts to overflow at the lower outlet.
  3. Move the hose to the higher end so that it creates a stream and washes sand down to the bottom end — observe the formation of the delta.
  4. Observe how the delta builds out (progrades) into the water.
  5. After about 10 minutes dump the colored sand into the stream and let it be transported onto the delta.
  6. After most of the colored sand has been transported, raise the outlet so that the water level in the tank rises to the higher level. — Note how the delta forms at a new place.
  7. After about 10 more minutes dump another set of colored sand and allow it to be deposited on the delta.
  8. Now lower the outlet to the original, low level and observe what happens.
  9. After about 10 minutes, turn off the hose and drain all of the water from the tank.
  10. When the tank is dry, use the shovel to excavate a trench down the middle of the sand tank to expose the cross-section of the delta.


1. How did changing the water level affect the formation of the delta.


2. When you excavated the trench, did you observe the layers of different colored sand in the delta? Draw a diagram showing what you observed. Describe what you observed here.


3. Was this a realistic simulation of the way oil reservoirs are formed. Please describe all of the things you think are accurate, and all of the things you think are not realistic?


Citing this post: Urbano, L., 2012. The Geology of Oil Traps Activity, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

Observing the Venus Transit

June 6, 2012

Shadow of the planet Venus during it's transit of the Sun on June 5th, 2012 at approximately 18:00 Central Time. Photograph taken from the MH Solar Observatory in St. Louis, MO, USA.

It’s pretty amazing how ecstatic seeing a simple circle with a little blobby dot can make a person feel. Following Ron Hipschman’s instructions, I installed a small aperture (~0.5 mm) solar projector at the newly established Muddle Home Solar Observatory (MHSO). The kids and I used it, and SunAeon’s app, to observe Venus transiting the Sun. It was, in a word, awesome.

The MHSO's small aperture (pinhole), solar projector.

For us the transit occurred late in the day, so by the end we had trees getting in the way.

Trees beginning to obscure the Sun.

If it seems odd that the trees are at the top of the image, it’s because the images in pinhole projectors are inverted. If I flip it around the right way, the image would actually look like this.

Corrected (inverted) image from the pinhole projector.

Citing this post: Urbano, L., 2012. Observing the Venus Transit, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

A Model Solar Water Heater

May 13, 2012

One of the middle-school projects is to build a little solar water heater. By simply pumping water through a black tube that’s sitting in the sun, you can raise the temperature of the water by about 15°C in about 15 minutes.

The solar water heater in action.

Next year I want to try building an actual solar water heater, similar to the passive air heater my students built two years ago, with the tubing in a greenhouse box to see just how efficient we can make it.

Citing this post: Urbano, L., 2012. A Model Solar Water Heater, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

Harvesting and Processing Chickens

May 4, 2012

We successfully harvested and processed three chickens during last week’s interim. It was my first time going through the entire process, but fortunately we had a very experienced guide in Dr. Samsone who also happens to be a vet.

The interim focused on where food comes from (students also saw the documentary “King Corn”), and the cleaning of the chickens was tied into our Biology students’ study of anatomy (I’d done fish and squid before). Unfortunately, I was unable to find someone who knew how to read the entrails so we could tie the process into history and language arts as well.

Student holds a kidney. A heart is in the background.

When we were done with the processing and analysis, Mr. Elder cooked the chickens on our brand new grill (which worked quite well he says). The chickens were free-range (donated by Ms. Eisenberger), but a little on the old side, at about 7 months old; the chickens you buy at the grocery are somewhere around 2 months old.

Dr. Samsone recommended that next time we raise the chickens ourselves from chicks, which I’d love to try, but I suspect would run into some serious resistance from the students. We’d only had the chickens we harvested for five minutes before they’d all been given names. Raising chickens from chicks would bring a whole new level of anthropomorphizing.

Chicken on the grill. The culmination of the interim.


Being new to the chickens, I spent a bit of time researching how it is done.

Ken Bolte, from the Franklin County Extension of the University of Missouri, recommended the University of Minnesota’s Extension site on Home Processing of Poultry (the page on evisceration provided an excellent guide), as well as Oklahoma State’s much briefer guide (pdf).

Dr. Samsone recommended the series of videos from the Featherman Equipment Company. Videos are particularly useful for novices like myself.

Herrick Kimball’s excellent How to Butcher a Chicken is also a great reference.

Citing this post: Urbano, L., 2012. Harvesting and Processing Chickens, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

Global Temperature Model: An Application of Conservation of Energy

August 19, 2011

Energy cannot be either created or destroyed, just changed from one form to another. That is one of the fundamental insights into the way the universe works. In physics it’s referred to as the Law of Conservation of Energy, and is the basic starting point for solving a lot of physical problems. One great example is calculating the average temperature of the Earth, based on the balance between the amount of energy it receives from the Sun, versus the amount of energy it radiates into space.

The Temperature of Radiation

Anything with a temperature that’s not at absolute zero is giving off energy. You right now are radiating heat. Since temperature is a way of measuring the amount of energy in an object (it’s part of its internal energy), when you give off heat energy it lowers your body temperature. The equation that links the amount of radiation to the temperature is called the Stefan-Boltzman Law:

 E_R = s T^4

ER = energy radiated (W/m-2)
T = temperature (in Kelvin)
s = constant (5.67 x 10-8 W m-2 K-4)

Now if we know the surface area of the Earth (and assume the entire area is radiating energy), we can calculate how much energy is given off if we know the average global temperature (the radius of the Earth = 6371 km ). But the temperature is what we’re trying to find, so instead we’re going to have to figure out the amount of energy the Earth radiates. And for this, fortunately, we have the conservation of energy law.

Energy Balance for the Earth

Simply put, the amount of energy the Earth radiates has to be equal to the amount of energy gets from the Sun. If the Earth got more energy than it radiated the temperature would go up, if it got less the temperature would go down. Seen from space, the average temperature of the Earth from year to year stays about the same; global warming is actually a different issue.

So the energy radiated (ER) must be equal to the energy absorbed (EA) by the Earth.

 E_R = E_A

Now we just have to figure out the amount of solar energy that’s absorbed.

Incoming Solar Radiation

The Sun delivers 1367 Watts of energy for every square meter it hits directly on the Earth (1367 W/m-2). Not all of it is absorbed though, but since the energy in solar radiation can’t just disappear, we can account for it simply:

  • Some if the light energy just bounces off back into space. On average, the Earth reflects about 30% of the light. The term for the fraction reflected is albedo.
  • What’s not reflected is absorbed.

So now, if we know how many square meters of sunlight hit the Earth, we can calculate the total energy absorbed by the Earth.

The solar energy absorbed (incoming minus reflected) equals the outgoing radiation.

With this information, some algebra, a little geometry (area of a circle and surface area of a sphere) and the ability to convert units (km to m and celcius to kelvin), a student in high-school physics should be able to calculate the Earth’s average temperature. Students who grow up in non-metric societies might want to convert their final answer into Fahrenheit so they and their peers can get a better feel for the numbers.

What they should find is that their result is much lower than that actual average surface temperature of the globe of 15 deg. Celcius. That’s because of how the atmosphere traps heat near the surface because of the greenhouse effect. However, if you look at the average global temperature at the top of the atmosphere, it should be very close to your result.

They also should be able to point out a lot of the flaws in the model above, but these all (hopefully) come from the assumptions we make to simplify the problem to make it tractable. Simplifications are what scientists do. This energy balance model is very basic, but it’s the place to start. In fact, these basic principles are at the core of energy balance models of the Earth’s climate system (Budyko, 1969 is an early example). The evolution of today’s more complex models come from the systematic refinement of each of our simplifications.

Advanced Work

If students do all the algebra for this project first, and then plug in the numbers they should end up with an equation relating temperature to a number of things. This is essentially a model of the temperature of the Earth and what scientists would do with a model like this is change the parameters a bit to see what would happen in different scenarios.


Global climate change might result in less snow in the polar latitudes, which would decrease the albedo of the earth by a few percent. How would that change the average global temperature?

Alternatively, there could be more snow due to increased evaporation from the oceans, which would mean an increase in albedo …

This would be a good chance to talk about systems and feedback since these two scenarios would result in different types of feedback, one positive and one negative (I’m not saying which is which).

Technology / Programming

Setting up an Excel spreadsheet with all the numbers in it would give practice with Excel, make it easier for the student to see the result of small changes, and even to graph changes. They could try varying albedo or the solar constant by 1% through 5% to see if changes are linear or not (though they should be able to tell this from the equation).

A small program could be written to simulate time. This is a steady-state model, but you could assume a certain percent change per year and see how that unfolds. This would probably be easier as an Excel spreadsheet, but the programming would be useful practice.

Of course this could also be the jumping off point for a lot of research into climate change, but that would be a much bigger project.


Yochanan Kushnir has a page/lecture that treats this type of zero-dimesional, energy balance model in a little more detail.

Citing this post: Urbano, L., 2011. Global Temperature Model: An Application of Conservation of Energy, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

Resurrecting the greenhouse

August 30, 2010

Two years ago, the middle school’s flagship project was to put up a fully functional greenhouse (using this design). It took all year but we did it. On the way, we got to practice geometry, mapping and construction, while learning and growing plants and studying soil profiles. It was so successful that, with our spring plant sale we broke even on the entire project.

Last year, however, the greenhouse was somewhat neglected. My plans to add an automatic window opener, which would have been a wonderful tie-in to our electronics and Newtonian physics studies, did not work out; we just did not have the time. We’d taken the plastic covering off, so only the bare, forlorn PVC frame was left standing around a plot of waist-high weeds.

Though I could not have predicted it, this year we have a strong core group of students who are highly enthusiastic about resurrecting the greenhouse and making it work. My suggestion was that we try to grow produce this fall that we could cook in December when we do our Dinner and a Show. Well, two weeks in, they’ve already put together a menu plan, weeding is well on its way and I’m being harassed to hurry up and arrange a trip to Home Depot. The excitement is so infectious that another student has volunteered to bring in his electric weed-whacker during the immersion. It’s amazing!

I’m having the hardest time not butting in. There is a beauty in seeing a well oiled machine executing a project or solving a difficult problem. But there is another even more wonderful aesthetic visible in a the birthing struggles of a nascent team. The forward motion of infectious enthusiasm is pulling puzzle pieces into its wake, and the pieces just seem to click into place when the time is right. I have to keep reminding myself that my job is to prepare the environment and let the kids do the rest.

Citing this post: Urbano, L., 2010. Resurrecting the greenhouse, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

Help with gardening/greenhouse

July 4, 2010

The National Gardening Association website has a wealth of resources for managing a garden. Including regional reports:

For the middle-south, “With year’s hottest and driest weather just ahead, it is best to delay the planting of tress and shrubs until autumn, when the odds of successful establishment are more favorable.” – St. Claire, 2010

They also have some nice how-to videos and instructional pages on topics like planting tomatoes and starting vegetable seeds (for the plant sale).

Citing this post: Urbano, L., 2010. Help with gardening/greenhouse, Retrieved April 21st, 2018, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

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