For one week each year
or so, we trade in our views of Zion’s red rock country for a cottage on
Maine’s mid-coast, with the open Atlantic at our doorstep, and where we awaken
each day to the sound of breaking surf, circling gulls, and nearby lobster
boats. For seven days, our comings and
goings are geared to the life of the harbors and coves we haunt. And so it has been a ritual with me over the
years, to construct, and carry with me on a pocket card, the local tide tables
which govern so much of that life.
At some point in the
formation of that part of the Milky Way Galaxy we call our solar system, a
Mars-size planetesimal collided with the infant earth in what would have been
an astronomical event of catastrophic proportions. The collision changed forever the destiny of
our planet, slowing its rotation, altering the atmosphere, increasing the mass
and density, setting the stage for the formation of the oceans, and ejecting 5
billion cubic miles of earth’s outer shell into space.
In another eon of time,
that halo of orbiting debris coalesced into a satellite we call the Moon. At one time, the moon was thirteen times
closer to earth than it is today. It is
fortunate for us that that spiraling journey (which continues) took place,
since it leaves us with a near-perfect relationship between two heavenly bodies
which act upon each other in a kind of harmony which affects literally every
aspect of earth life. And that brings us
back to the subject of ocean tides.
While the Sun because of
its immense size, as well as the Moon because of its proximity both influence
tidal action on earth, the moon is the primary gravitational partner when it
comes to time and tides. In fact, it is
only when we think of the earth and the moon acting together as a single
gravitational system that an understanding of tidal dynamics becomes
clear. Most days, there will be two
high tides and two low tides except for several deviations each month owing to
the fact that it takes the moon just under 25 hours to make its circuit of
earth. Because the earth’s greater
gravity also plays a big role, the centrifugal forces generated by earth’s
rotation “throw” the seas outward on the side of our planet opposite the
moon-side producing similar (although slightly lesser) tides on that side as
well. The highest tides occur when the
sun, the moon and earth are in a direct line, as at a full moon, a new moon, or
during a lunar or solar eclipse.
There are many other
factors at play such as the depth and shape of the sea floor and the narrowing
of tidal approaches. Most of New
England’s harbors experience tide depths of 8 feet to 12 feet, while the Bay of
Fundy between Maine and New Brunswick will see miles of muddy sea bottom when
out-flowing tides of 50 feet or more
leave boats high and dry as far as the eye can see. At the reverse end of this cycle, the volume
of the incoming tide can push mountains of seawater – called a tidal bore –
into those same narrow harbors and estuaries.
Dangerous whirlpools and unpredictable current surges are all part of
coastal navigation and small-boat handling challenges for “Down East”
fishermen, in addition to some of the most violent storm activity anywhere on
our planet. (One unforgettable day I was caught standing on the low-tide shore
when an approaching bore pushed an unexpected “wind” of such force before it
that I was almost swept aside before I could reach high ground!)
It is worthy of note
that every lobster we harvest, every clam we dig, and the very circadian rhythm
which allows us to sleep soundly during the long hours of restful darkness at
the end of each earth-day, are gifts of time and tide.
Each and every time I
stand at the tip of my favorite rocky peninsula, and view with never-ending awe
the spectacle of land and sea there at the continent’s edge, I give a silent
thanks to be a citizen of Planet Earth.
-001.jpg)
West Quoddy Head, the eastern-most tip of
continental America near Lubec, Maine, just 3 months after the author had photographed the lighthouse at Cape Blanco, Oregon – the
continent’s westernmost point. Al Cooper Photo
“Old Sow” whirlpool showing tidal power in
Bay of Fundy. Courtesy Jim Lowe,
Posts
No comments:
Post a Comment