Saturday, November 8, 2008

Teaching tides

Slate gray sky above, slate gray water to my knees. The water's still warm enough to wade in, and the tide was creeping in over the clam bed.

The few splashes of color--a jumping bluefish, a few scoters scooting by--looked pixellated against the dull light.

I scratched up enough clams for dinner,and a few more for my Auntie Beth, then paddled a longer route home.

It was a gorgeous morning.

Clamming lets you see things you forget you care about. Clams are in no hurry to escape; the only urgency is the rising tide.

Humans are very good at assimilating information, finding patterns, creating a more perfect vision of the world. Tide heights vary over a 19 year period, depending on where the moon and sun happen to be, and you can find nice graphs with smooth, curves that even supermodel Heidi Klum could envy.

We teach about tides in school, of course. Understanding tides requires grasping geography and gravity, winds and water, mathematics and models (of a different sort).

I confess I do not fully "get" tides, despite a decent education, but I'm going to talk about them anyway.

Tides around here happen about twice a day. Tides change fastest between the peak highs and lows, or mid-tide.

You can watch the tides rise and fall. Literally. And while the tidal flow does, indeed, peak around mid-tide, it does not rise as smoothly as your textbook might suggest.

I clam at the edge of water. The edge rises perceptibly as I work. The edge's personality changes over the couple of hours I rake.

It creeps up stealthily, smoothly, for a few minutes, then takes tiny staccato steps for a few more. It pauses. It retreats for an instant, then surges a bit more.

The edge does not define the tide. It's jerky journey up towards the debris left by the last high tide reminds me what we cannot know.

In school we teach the big ideas, the grand illusions, and we lose touch with the local.

Humans define the tide on a grander scale than a sandy patch of Richardson Sound lying next to an abandoned railroad. We can know averages, we can know tendencies, and we can make wonderful predictions based on our grand scheme of things. People who can make good predictions can make a lot of money.

Still, to know the tide, to understand something about it, you need to watch it push the edge of the sea, washing away the footprints of your feet.

Graph and photo lifted from NOAA; the caption for the photo reads:
"Taking boat for a walk over the mudflats. If the tide goes out and you anchor high, you might have to do this."


Anonymous said...

I just sent a link to this post to my current marine biology students.

Growing up in Missouri... none of us know tides in any "local" sense.

However, in April, we will once again live in the middle of nowhere (Andros Island, Bahamas) for eight days experiencing one of the fundamental rhythms of the planet.

This puts a slant to tides that my students haven't seen to this point... thanks!


doyle said...

Your students are lucky to have you lead them.

The tide still amazes me every time I watch it rise and fall.

I grew up near the shore, then moved away for years.

I am incredibly blessed to know the tides again.