Tuesday, August 14, 2012

Ocean Studies: Tides

In First Grade (at least in our curriculum) kids are expected to be introduced to the phenomenon of tides.  Only the idea that the tides mean the water goes higher and lower at different points of the day is required at this age, but if, you have a curious child it is unlikely the conversation will end at this fact. 

You may want to make sure that your child first knows that most of Earth's surface is covered by water.  For an activity to demonstrate this fact (and also help your older child practice calculating percentages, or your younger child practice counting to 100) click here.

The trouble with teaching about tides is, tides are actually pretty difficult to explain - especially for a more visual kid.  I would personally begin by showing them a "tide". 

If you live near the ocean or have an opportunity to vacation near the ocean, this is an easy thing to do.  Go out at high tide and mark the tide in some way.  If you live on a sandy beach, simply poke a stick into the sand.  If you are on a rocky shore this is a little more difficult, but depending on the substrate, a chalk line might work, a Large unique stone set in place might work, or any number of other "creative" markers can be helpful.  Then, as the day continues keep checking on your marker and notice how the water level changes during the day.  Make sure to point out to your young one that there are two high tides and two low tides every day.

If you do not live near the ocean, actually showing a tide can be difficult.  Instead, you can represent one.  Get a painter's tray (you know, the slanty ones for using rollers for painting) and fill it half-full with water.  Now, press a ball or balloon into the tray part to show how the water can move up and down the beach (this idea was inspired by this activity.  It is incorrect that the moon pulls the tides high only on the side closest to the moon so please don't just leave it at that). 

Either way, I also recommend viewing either, "Curious George: The Time of Sands" or "The Blue Planet: A Natural History of the Oceans" series, season one, episode seven, "Seas of Life; Tidal Seas" for your older kids.  Right at the start it has gorgeous time laps video of high and low tides along a couple of distinctive coastlines followed by a description of the cause of the tides.  Curious George is perfect for Preschool - 2nd or 3rd grade, but then the vocabulary in "The Blue Planet" for many older elementary kids.  For this age group, it might be best to watch the clip of the time lapse video, and then do the activities that follow.  For older children, I might show this video if you also plan to study marine biology.

Now to explain why the water rises and lowers twice each day is a little more difficult.  Many adults that are very intelligent have trouble understanding this one without visuals so it is important to include visual aids.  It is NOT impossible to understand and your child can get this.  You may want to quickly explain the basic existance of gravity if your child has not already learned about gravity.  If your child already has a basic handle on gravity go ahead and skip to the video link below.

The way I introduced gravity to Alice, was to tell her that all THINGS (matter) that can be touched or contained in some way have gravity.  This means that all things pull on one another a little like magnets pull on one another.  I actually said, "so that means you and I are both pulling each other closer together all the time.  If we weren't on Earth and were near one another, we would actually slowly move together until we were touching.  We couldn't help it, its just what would happen."  I continue, "but bigger things have more gravity so while we pull on each-other and we pull on the Earth, the Earth pulls on us a LOT MORE".  I further explain that even if we push on the Earth (Jump here), the Earth pulls us back and it takes rocket-sized power to push hard enough to leave Earth.  I then transition back into tides by saying the Moon and the Earth are always pulling on each other. 

I then transitioned her into watching the video in this link.  I suggest opening a duplicate window before you click.  Actual Explanation done with a cookie, pickle, orange and string (best I viewed)  This explanation is pretty complete yet clear and concise.

To explain about the Tidal Bulge on the side of the Earth opposite the moon and why the cookie moves in the video I suggest this short activity because it really worked with Alice:

I made sure we were in a large space and showed Alice the Moon/Earth "orbit" by spinning together. I held her hands with my wrists crossed and we turned a few circles quickly (but so she could keep her feet on the ground) together this way.   I had to move a little bit as the anchor, but Alice moved more as she spun around me. I told her that the Moon and Earth are a bit like us spinning around each other.  I was the Earth and Alice was the moon.  If I was able to have a bunch of water surrounding me she would pull back on me and her pull would move the water around me more than it would move the land and she would be able to see a bulge going toward her.  The point is that she sees me move slightly in a small circle around myself. 

As I was writing this blarticle I found this activity which furthers the experience and just extends the understanding a child gains from the "spinning" activity.  It will require a few materials and use of a drill by the adult during prep.

For More Related Videos: click here

For more Images, Extensions and more Links about Oceans and Ocean Tides for kids of all ages, try Enchanted Learning, Teacher Planet, and/or How Stuff Works

Good Luck, have fun and please let me know about any other great additional activities you've discovered!

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