Saturday, November 6, 2010

Module V - Ocean Systems

Explain - What new learning have I taken from this module?

Extra bouyant in the
Dead Sea
I found this module to be a fascinating one.  Ever since I was a kid I've been astounded by the superlatives of the ocean:  the 40,000-mile mountain chain, the depths able to swallow Mt. Everest, the worlds tallest mountain, the draw of over half of humanity to it shores - the list goes on and on.  As an adult, I became familiar with the significance of density diffences and temperature differences in the oceans through education, scuba diving and travel.  This module was a great synopsis of the factors effecting ocean currents,  world weather, resources and, ultimately, human societies.  I found the 1000- to 1600-year journey of a water molecule through the depths of the ocean to be fascinating.  Ever since doing some Cenote diving in the crystal-clear, fresh water of the Yucatan Peninsula's limestone caves, the halocline has fascinated me.  There, you can actually see the interface between fresh water and the salt water below.  It looks like a layer of clouds through which you can't see clearly from either below or above.  Check out this Youtube video of some divers going through a distinct halocline.  Every diver who has been in both fresh and salt water is familiar with the fact that you need more weights to compensate for your bouyancy in denser salt water than in fresh water and divers in the Dead Sea must need even more.

Extend and Evaluate - How can I use this week's resources and how useful, insightful or relevant are this module's information resources to me?

San Francisco at 37 degrees
46 minutes North
The most useful resource that I found in this module was the last half of the video about Ben Franklin's discovery of the Gulf Stream.  I found the animation of not just the warm surface current, but also the cool water dropping to the sea floor and returning to the Tropics to be a very good illustration of a fairly complex idea.  I would love to see such an animation that follows the entire 1000-year journey of a water molecule, but have been unable to do so, as yet.  I liked the demonstration with the lighter under the balloon.  It reminded of a trick I learned in Boy Scouts in which you can boil an egg in a paper cup over a campfire.  The paper burns away above the waterline, but stays intact where it's in contact with the water.  The exercise in GoogleEarth was also instructive, though I was unable to get the ocean temperature overlay to work.  I did, however, find a NASA image that shows the  difference between ocean surface temperatures on the two coasts of the U.S.  The cooler west coast waters certainly explain the cool, foggy summers of San Francisco, though the reason for Washington D.C.'s harsher winters is not as clear.
Washington D.C. at 38 degrees
53 minutes North
 
NASA image of ocean surface
temperatures











 



Blue, glacial meltwater staying atop salt water
at the Columbia and Valdez glaciers

 I also thought that the experiment with melting blue-colored ice in warm, red water, would be very demonstrative in showing the difference in density of cool and warm waters.  Finding evidence on GoogleEarth of a similar phenomenon would be very instructive for students, though I was disappointed to find no evidence of this at the mouth of the Amazon River.  This, despite that fact that sailors of previous centuries were able to encounter less-dense fresh water atop ocean water days before arriving at the mouth of said river.

 Three collegues and three comments

I enjoyed the link on Tyler's blog to the beachcomber's alert site that showed how you can learn about ocean gyres by beach combing.

Amy's blog pointed out how incredible it is that Ben Franklin was able to map the Gulf Stream so accurately without the use of GPS or modern scientific equipment.

Janet's blog had a great link to the Oceans Alive website with a map in which Pangea is reunited - a great visual to show how much of the planet is covered by oceans.


1 comment:

  1. Neat video of the divers going through the halocline!

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