A Teachable Earthquake

When something unexpected occurs, either in the classroom or in the world, and it provides an opportunity to teach outside of the curriculum, educators refer to this as a "teachable moment."  The East Coast Earthquake of 2011, centered in Virginia, is an example of a "teachable" event that actually fits conveniently into our curriculum for sixth grade.

After our study of plate tectonics, we have moved on to look more closely at the catastrophic byproducts of plate movement - earthquakes and volcanoes.  As we studied earthquakes, however, the earthquake that we all experienced just a few weeks ago has become a meaningful piece of experience that the kids all share with the concepts covered in class.

Once we had explained the causes of earthquakes, as well as the concepts of the focus and epicenters of quakes, we were able to examine the USGS maps of the 2011 East Coast Earthquake.  Since several of our students were on vacation in several different spots along the east coast, we were able to plot their locations and their experience based on the epicenter and magnitude diagram shown below. 

Most of our students knew several facts and had lots of questions about the earthquake based on the news coverage from that day.  To further explore their memory of the quake, we watched news footage of the breaking story.  The video below includes security camera footage of the shaking at the White House. 



Overall, the kids could much more easily relate to the feeling of a quake given that they had just experienced a historic one just a few weeks ago.  

Convection Currents

So far, we have examined Earth's plates and how they move, as well as what occurs at convergent, divergent and transform boundaries.  But why are the plates moving?

Tectonic plates are floating above a plastic-like layer of magma material in the mantle.  The intense heat in this layer causes convection currents.  Convection currents are circular patterns of heat in liquids and gases.  Generally, hotter material is less dense and cooler material is more dense.  As material nearest to the outer core is heated, it becomes less dense and moves upward above the cooler material above.  As it moves closer to the crust, however, it cools, becomes more dense and begins to sink again, creating a circular current of heat movement.  Depending on the direction of these currents, the plates slowly move together, apart, or past each other. 

The phenomenon is visible in heated water, as well.  It happens much more quickly, of course, but it makes for a good demonstration in class. 

For this lab, we place beakers of water onto a lab burner.  I usually place a few beakers on each burner so that the demonstration can be attempted a different temperatures or multiple times.  As the water heats, students answer discussion questions on their lab sheet including, "which part of the beaker is the hottest?" and "which part of the mantle is hottest?"

As the water heats, add a drop or two of food dye into the water.  The students must watch closely because the dye will become completely mixed into the water very quickly, especially if the water is already very hot.  On their lab sheets, they should draw as accurate of a sketch as possible to show the circular currents of food dye in the water.  Once the dye becomes completely mixed, the convection currents are still occurring, it is just no longer visible. 

Below are some images of the circular currents in action:

Spreading the Word about Seafloor Spreading

Inevitably, as soon as we finish explaining how the continents could have drifted apart, the questions start rolling in about how this could have happened.  Luckily, the next section in our notes and our next "lab" answers just that question!

The process of seafloor spreading is what causes the continents to slowly drift apart.  Running down the middle of the ocean is a mid-ocean ridge - a crack between two tectonic plates.  At the mid-ocean ridge, the fiery hot convection currents of magma below the crust exert intense pressure and push the two plates slightly apart.  The magma oozes into the crack that is created and creates new seafloor and the ocean becomes gradually wider, forcing the two continents apart. 

On the opposite end of the plate, the pressure collides the plate with another plate.  Generally, these plates converge and one dips below the other.  As it delves deeper into the mantle, it is heated and melts back into magma, thus continuing the cycle.

In order to model this phenomenon, we created a simple model out of construction paper, glue and masking tape.  I prepared ahead of time by cutting out brown construction paper to model the tectonic plates.  I cut 9" x 12" paper into 4" x 4" squares.  Each group will need four of these squares.  For each group, take two of the squares and tape them together with masking tape end to end.  The other two will stay separate. 

We created mock magma by combining white school glue with red and yellow food dye and mixing it with a popsicle stick in a small paper cup.  The students then spread the magma in a thick stripe down the middle of the large sheet of white paper.  We placed the taped together plates and the loose plates over the strip of magma touching end to end with the intersection over the strip.  At the far ends of the brown paper, we taped them loosely to the white sheet just to hold them in place.  Finally, we were ready to model the process. 

The students slowly slide the plates apart over the magma and watch as the magma rushes in to fill the crack.  As the magma cools, new seafloor is formed and the ocean is wider.  On the other side of the plates, they meet another plate and the intersection either rises like a ridge or mountain range, or it dips below another plate.  Both of these possible outcomes are shown on the model. 

I provided the students with a sheet of labels to apply to their diagram.  They simply cut out the labels and applied them where they belong.  Below are some images of the works in progress, and a completed sample:

Piecing Pangaea

Each year, the first order of business in sixth grade science is to cover plate tectonics.  This is one of the most difficult and abstract concepts that we cover all year, and it falls in the very first two weeks of their middle school transition. 

In order to demonstrate how scientists were able to piece together Pangaea, we begin by examining the current map of the world.  The earliest conjecture about the existence of a 200+ million-year-old subcontinent was probably German meteorologist Alfred Wegener, and his first clue was the puzzle-like fit of the continents together.

As a quick activity after students have read and taken notes about continental drift, they cut a map into continent puzzle pieces and explore how neatly they fit together.  Eurasia has significantly changed in size and shape since the time of Pangaea, so we emphasize how neatly the eastern coast of South America and the western coast fit together, as well as how neatly the east coast of the United States fits with the northwestern coast of Africa. 

Wegener also had a few more clues about how the continents may have been connected.  Students read about the fossils of the pre-dinosaur reptile Mesosaurus and that those fossils were found in both South America and Africa, leading Wegener to hypothesize that these continents must have been connected at one time.  When Mesosaurus roamed the earth, they populated a large region of Pangaea that is now separated onto two continents.

As a meteorologist, he was also interested in climate-related evidence.  Fossils of warm-weather plants have been discovered as far north as the Arctic island of Spitsbergen.  Again, this suggests that islands like Spitsbergen have changed their location and when they were connected to another continent, they were in a warmer climate. 

In order to model this concepts, the students use a large piece of construction paper and cut it into an irregularly shaped "supercontinent" of their own design.  Then the students glue populations of fossils onto the continent.  Finally, students cut their supercontinent into several smaller, irregularly shaped continents.  They were instructed to make sure to cut their continents in such a way that at least a few boundaries cut through the populations of Mesosaurus, Glossopteris, glacial remains and the other fossils provided. 

The following day, I switched up the puzzles and gave each group a mystery supercontinent that was created by another group.  Students had to rebuild the supercontinent based on the same clues that Wegener used - the puzzle-like fit of the continents and the fossil remains of species. 

Below are some images of the students' supercontinents:

The students really enjoyed this project and showed a must stronger grasp of the concepts as a result.  Next time, we tackle the much messier project to demonstrate seafloor spreading!

Did You Know?

During my summer of relaxation and recuperation, I found myself flicking through the channels on my old-fashioned tube television - you know, the kind that doesn't have a flat screen, HD reception or a nifty guide for viewing the program schedule.  In my search for something appropriately mindless, I passed over the public media network MiNDtv, known for it's short videos, often submitted by viewers or other sources.

The short film airing at that time was called, "Did You Know?" and it was a simple video that featured facts about Earth's population and growth, as well as many facts about the exponential growth of technology.  The video can be viewed on the MiNDtv website here:

http://mindtv.org/cgi-bin/display_asset.fcg?member_id=1776;ordinal=1182;file=vodind-new.ttml;style=mind

Naturally, there has been a huge emphasis on technology in education recently, but this video forced me to face how important this really is.  The truth is, no matter how memorable certain lessons and experiences were from my own education, some of these approaches are just not practical anymore.  By schooling a child, we should not only be preparing them with the academic skills and knowledge that they will need, but also a steady footing in the technology that is available today. 

My education was not very long ago and we had a full lab of computers with internet access, databases for research and other tools.  But technology has changed significantly since I was in school, and it will change even more in the period between these students' education and their adulthood.  There is no way to prepare them for the technology of tomorrow other than increasing their fluency with the technology of today. 

The original video has been updated several times to reflect new statistical research about the changing world of technology.  The updates are aptly titled 2.0, 3.0 and 4.0.  They are all embedded below.

Material Worlds

In the past, I have taught a lesson a few times using pictures from the photo-essay, Material World.  The collection of photographs found families that reflected the statistical average income, family size, and household for each of several selected nations.  The families, who were visibly proud to participate, were asked to sit in front of their home with all of their possessions.  The images are compelling, to say the least.

Not only are the images from India and Mali, among others, surprising to most of my students, the picture of the average family from the United States may have been more so.  Kids in the class are already aware that most families of the world live with fewer belongings and resources than they do, but many truly believe that they are average within the United States.  It was interesting to see their responses to what is truly average in the United States, as well as how much poverty can exist in the world's richest and most powerful country.

Below are some images from the Material World book, documentary and photo essay:


The Wu Family of China


The Yadev Family of India


The Natomo Family of Mali


The Skeen Family of the United States

All images are copyrighted to Peter Menzel.  Source: http://www.pbs.org/wgbh/nova/worldbalance/material.html

I was excited to learn that there is a new, similar photo-essay created more recently by James Mollison.  In his pictorial essay, he allows us to see into the lives of children through photographs of where they sleep each night.  Where Children Sleep shows many children from the United States, as well as from several other nations, showing everything from overflowing toy shelves of beauty pageant crowns and dolls to a mattress with scattered blankets next to railroad tracks in Italy. 

Middle schoolers are, perhaps, at the perfect age to begin to see and truly understand the strata between rich and poor both in the United States and around the world.  In the past, we have always had fruitful discussions about these images, and I was excited to hear that there was another more current photo-essay. 

You can see twenty images from Mollison's book on the New York Times "Lens" blog, linked below.

New York Times Lens Blog - Where Children Sleep