Sunday, October 17, 2010

Surf's Up!

Just one more post left in me from our trip to Puerto Penasco, MX last weekend! One of the things catalogued under "often observed, but rarely noticed", are ocean tides, caused by the gravitational attraction of the sun and moon on the Earth's oceans. For a farm boy raised in the Midwest and living in the Southwestern desert, large bodies of water are amazing enough, but tides are an amazing subject in themselves. But that isn't the point of tonight's post - check out the Wikipedia link to tides to learn more...

No, what is amazing to me is that the Sea of Cortez has the 3rd highest tides in the world! After the Bay of Fundy and a bay in southern Alaska, the tides at Rocky Point can routinely exceed 6 meters (20 feet) near new and full moon. Why is the Sea of Cortez special - well, it is because it is enclosed on one end, and once the water starts flowing down the relatively narrow body of water, it has no place to go but slosh up the bank on the end like a kid playing in a bathtub. There is a way-cool simulation demonstrating it here. In the photo above, taken near low tide, I was standing on the high tide mark left about 6 hours earlier. There is well over 100 meters of exposed beach to get to the water!

We lucked out Saturday morning - after staying up late observing Friday evening, we got to sleep in - low tide happened about 8:30. I set up my camera and tripod on the beach, and took a LONG sequence taking images every 2 minutes. The movie made from the total is sizable, and for those with limited bandwidth (Hi Sister Kathy!), I've included 3 images taken an hour apart to show the change over just 2 hours.

For those of you with faster connections, click on the image here to see a 1.5MB movie GIF that covers 2.5 hours of incoming tide. With that shallow extent of beach, it was interesting to watch some kids digging in the sand, go splash in the surf for a few minutes, then have to rush to retrieve their play implements before they washed away - it really did come in that fast! Depending on how well this gif shows, I've got other sequences of sun and moon set from seaside, so we might yet return to Mexico once again on the blog... Well, it isn't working, so I need my blog expert debugger Melinda to assist, so come back later for the movie! (From Melinda: Fixed!)

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