Monday, February 20, 2017

How Big a Splash Does a Rock Four Kilometers in Diameter Make?

When I started writing curriculum, I was told to tell a story.  The lessons needed to be joined together in a coherent storyline.  The theory was that students would learn more if they knew how the concepts were linked together.  In the age of the Next Generation Science Standards (NGSS), this idea is amplified further with the addition of engineering design challenges.  Not only do the lessons need to connect, but they need to connect towards solving a problem.  As an example, I will walk you through a unit was just updated.

The performance expectations for this unit are from the grade four topic page "Earth Systems: Processes that Shape the Earth".  Maryland has some diverse geological features, but rarely do we have any that cause a disaster.  In 2011, we did have an earthquake that registered 5.8 on the Richter Scale.  That is pretty much an extreme for us.  So, if I wanted to have local natural disaster, I would have to get creative.

As it turns out, Maryland has had some significant geological events.  The most significant happened 35 million years ago.  A bolide roughly four kilometers across smashed into the shallow waters in what would be the southern tip of the Delmarva Peninsula.  The super heated winds created a hypercane which vaporized everything within 1000 km.  The splash resulted in a tsunami which traveled to the Appalachian Mountains.

Location of bolide impact.

The story of the crater's discovery played very well into the performance expectation on changes in landscape over time.  The crater cannot readily be seen on the surface.  After 35 million years, erosion and sedimentation have erased most of the evidence (4-ESS2-1 and 4-ESS2-2).  Some of the conclusive evidence which identified the age of the impact conveniently was the result of fossil evidence (4-ESS1-1).   That leaves students having to develop ways to minimize the impact of  Earth's natural processes. 

Now, what I originally wanted to do was have students plan for another meteor impact.  In 2880, another meteor is projected to come close enough to Earth where it MAY impact.  NASA has some great simulations showing the potential for an Atlantic impact. However, apparently nine year olds would be sensitive to that even though it is well into the future.  So, I had to find an oxymoron- a non-threatening natural disaster.  As it turns out, the Canary Islands provide one. 

The island of La Palma has a slab of rock that may slide off into the ocean and cause a tsunami wave which could impact Maryland.  There was a story picked up by the media several years ago that over hyped a projected model.  A great lesson in science all by itself.  

After discussing how models can be used improperly, we talk about more realistic impacts from waves and equate them to some of the hurricane storm surges Maryland gets.  We go from mega-disaster to survivable threat.  The students are then tasked with build a tsunami resistant house.  I really liked the version from Teach Engineering.  I did modify the design a bit.  I went with a 1'x1' ceramic tile as my wave generator rather than a piece of sheet metal duct taped to the bottom of the tub.  Also, rather than pushing the tile down, I pull up.  It produces a much more consistent wave.  


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