The importance of Scientific Modeling

As Kenyon, Schwarz, and Hug point out "a scientific model is a representation of a system that includes important parts of that system (along with rules and relationships of those parts) to help us think about and test ideas of the phenomenon (2008)." I stress this point to my students almost on a daily basis by helping them understand the fact that models help us understand things when size or time would be a problem for making observations. I frequently use models to provide concrete examples of abstract phenomena to difficult to replicate in true life scale.

In our earth science unit I use several methods to demonstrate the structure of the Earth and plate tectonics.

In demonstrating the structure of the Earth I first have the students label and color a cross section of the Earth's layers with thicknesses (in km). Then I provide them with four rocks: granite, basalt, peridotite, and magnetite, and have the students find the volume and mass of each sample. From that data, the students can calculate the density of each of the rocks, and then I have them match up the rock type with each layer of the Earth: granite (continental crust), basalt (oceanic crust), peridotite (mantle), and magnetite (core). This helps students understand that density of rock is a major factor in why the Earth's layers are oriented in that fashion (lesson attached).

Next we move on to plate tectonics and to introduce this I use two oranges: the first is cut in half and the second has the peel cut into large sections and just laying on top of the orange. I first show students the half orange and tell them this represents the Earth, but not completely accurately. I next show them the orange with the peel sections lying on top like a jigsaw puzzle and explain that this is how the Earth's crust looks. I give each student a map with the seven major tectonic plates outlined and have them cut it out and lay it on their desk like a puzzle. To demonstrate plate movement they choose one plate and slide it slowly in one direction. I ask them to make observations about what is happening at the edges of each plate, then we discuss divergent, convergent, and transform plate boundaries.

To demonstrate the mechanism behind plate tectonics I use a lava lamp since it mimics the convection current in the mantle. Students make the association of the bulb being the core, the center liquid section being the mantle, and the top being the crust. We discuss how the liquid is heated near the core, floats to the surface, and then sinks back down. Now to take it a step farther in helping them understand how the plates move because of this convection I set up a hot plate with an aluminum pie pan with about three centimeters of syrup inside then add small graham cracker squares in the center on the surface (see before picture). I turn on the hot plate for about ten minutes or so and the convection current in the syrup has pushed the graham crackers apart (see after picture). Again, the students make the association of the model to the Earth: hot plate (core), syrup (mantle), and graham crackers (crust). This is one of my favorite models because it really ties together the structure of the Earth and the mechanism for plate tectonics. The students really like it because they get to eat mantle covered crust which is probably the only time in their lives they will get to do that.

I also use virtual models to illustrate plate movement as well as geologic activity on the plate boundary such as earthquakes and volcanoes. I use the Geologic History of the Earth animation from the SEED website to show how the earth has changed over hundreds of millions of years (2010). I also use real-time earthquake data from the USGS to demonstrate that earthquakes occur along plate boundaries because that is where plate movement is the most evident (2010). I have used the earthquake simulator and the volcano explorer websites in getting students to manipulate different variables affecting the outcome of each type of event (2010).

Modeling is a vital piece of bringing the abstract into the concrete for students to manipulate, test, and most importantly to experience science as it is meant to be.

References:
Discovery Communications. Make a Quake. (2010). Retrieved November 24, 2010 from http://tlc.discovery.com/convergence/quakes/interactives/makeaquake.html

Discovery Communications. Volcano Explorer. (2010). Retrieved November 24, 2010 from http://kids.discovery.com/games/pompeii/pompeii.html

Kenyon, L., Schwarz, C., & Hug, B. (2008, October). The benefits of scientific modeling. Science & Children, 46(2), 40–44.

SEED. Geologic History of the Earth. (2010). Retrieved November 24, 2010 from http://www.seed.slb.com/science_sublanding.aspx?id=26672

Keeping Science Current in the Classroom

Using current events in the classroom to drive home the classroom content aids the teacher in making science real for students. A couple of examples of this are the earthquake in Haiti in January and the volcanic eruption in Iceland in March.

When news of the Haiti earthquake spread I immediately pulled up a map of the Earth’s tectonic plates and pointed out Haiti then asked students why an earthquake would have occurred there. After allowing the students to discuss in their groups for a couple of minutes many were able to point out the fact that there is a fault line running through the country leading to the discussion of plate movement and how earthquakes occur. We then examined some of the photographs from Haiti paying particular attention to the structures of the buildings and how they were stacked on top of one another and did not appear very sturdy at all. Our school started a Haiti relief effort by collecting supplies to be delivered for displaced families on the island. That discussion and lesson did take the entire class period, but when a teachable moment presents itself, particularly one with heavy media coverage, then you go with it.

Another moment was in March when a fissure eruption opened up on Iceland. Again a map of plate tectonics graced my classroom and again discussion ensued. We discussed divergent plate boundaries and seafloor spreading. I showed them video clips and photographs of the volcano and asked them to imagine eruptions just like this one only on an unimaginable scale. We discussed the Siberian Trap eruptions from about 50 million years ago which lasted for about one million years and how devastating something like that can be to life on Earth, so devastating in fact that it wiped out 90 percent of all life on the planet at that time. Using this unique type of eruption allowed an opportunity to discuss how new crust is created as plates move away from each other.

Then I asked the students if there was a correlation between the Haiti earthquake and the Iceland volcano. Since they both lie on the edges of the North American plate, could movement at a fault zone in Haiti create the separation of plates at a fault zone in Iceland? From what we could determine, since the plates are giant solid slabs of rock, that movement at one end of the plate would cause movement at the other end of the plate.

Current events can be an invaluable resource as it allows the students to step outside of the vacuum of the classroom and experience science at a real-world level.