From diehard surf dudes to the cocktail-sipping elite of Saint-Tropez at one time we've all stared out at the mirror of the ocean and contemplated its waves, well they are a ubiquitous feature of our shorelines no two waves are ever the same, some curling over perfectly some surging chaotically up the beach to soak your trouser leg. But what are they exactly and where do they come from?
Well, you can
learn a lot by simply watching the waves cocktails are optional, 'no cocktails
are essential: seeing them lineup ready to break along the shore ocean waves
look like organized heaps of water that have traveled from far out at sea to
finally, wash up at our feet and when they break pushing up the beach, that
certainly seems to be the case but watching the procession of waves little further
out tells a different story. Sea birds and message bearing bottles float on the
surface of the sea and as a wave passes, we see them rise and fall but they
ultimately stay in roughly the same place, that's because it's not the water
that's heading for the shore it's the energy within the water.
As we all know, energy can't just be created
out of nowhere, the energy must come from somewhere. You might think that most waves
are caused by the Tides but you'd be wrong, sorry', you could say that tides
themselves are actually massive waves caused by the moon and the earth spin but
that's not what we think of as waves.
Some giant
waves are caused by catastrophic underwater earthquakes or weird
fluctuations in the atmosphere, but pretty much every wave you'll see in your
lifetime was caused by the wind. Even on a still day the way is breaking out on
the beach were born far away in a bluster. It all starts with still water, the wind
blowing across the surface drag some of the water along with it creating a
regular series of lumps that are known as Capillary ripples these are
only small and the surface tension of the water itself is enough to flatten
them back out again but if the wind keeps on blowing it's now got the lumps and
bumps of the Capillary waves to push onto, carrying them along
transferring more energy from the air into the water once they get a bit bigger
there now called Gravity waves, since now the wave is all about fighting
gravity trying to pull the water back to equilibrium rather than the water
tension. Out at sea the wind keeps blowing and the waves keep growing until the
whole of the surrounding area is known as a Wave sea, which basically
looks like a chaotic mess of choppy waves moving in all directions, more wind
usually thanks to stormy conditions helps Sea wave reach impressive
Heights they can stretch up to 10 (ten) meters from trough to peak in a fully
developed sea, once they've got enough energy from the wind waves spread out
from the wave scene and begin their long journey across the open ocean as Swells.
The size of waves in a Swell depending on how fast the wind was blowing
how long it was blowing for and the area over which it was blowing that's known
as The fetch and this is where it gets really cool because from what
I've described you know I've got waves of all shapes and sizes all traveling
across the oceans with different heights and spacings and speeds and it's all
thanks to the wonders of physics, that they tend to get bunched up in something
called Wave trains, separated by relatively calm water. Within these trains,
the positive interaction of different waves can pile the water even higher
until they reach astounding Heights. These Rogue waves, as they're known,
can seem to come out of nowhere and some have been reported to tower over three
stories tall, appearing to sailors like an unexpected wall of water in an
apparently calm sea. Neatly organized into their trains waves travel thousands
of miles uninterrupted across seas and oceans before they reach their dramatic
ends on our beaches and shorelines.
But how and
why do they build up and break?
Well remember,
it's not the water itself traveling all those miles from the middle of the
ocean to the beach, it's the energy within a traveling wave of energy the water
it passes actually follows a Circular orbit, first a little
backward, then up then a little bit forwards then back down again, this
movement tugs on the patch of water in front making it in a circular path and
that allows the wave of energy to move forward.
The water beneath
the surface is also affected by this movement it's encouraged to go in its own
small circles diminishing in size as you go down increasingly deep, and this
helps explain how a wave grows as it reaches the shore as it approaches shallower
water the circular orbit of the lower waters start to come into contact with
the seafloor and friction with that hard ground slows it down. Meanwhile, the
water above is less affected by the friction so it keeps going and it's
original speed and to get out of the way of the slower water beneath it the
only direction that can go is up, this makes the waves grow in height but
they're left unsupported as the lower parts drag along the seabed so eventually
a wave moving forward will find itself with nothing underneath it at all it
collapses into a dramatic breaker. And the type of breaker you get depends on
how steep the beach is beneath the waves, shallowly dipping shorelines
encourage spilling breakers that collapse in a chaotic sway of the foam. While
steeper beaches produce plunging breakers where the water curls over, in those
perfect tubes sought out by the surfing pros.
So, waves
are really just energy. Energy making water travel in circles and energy being
passed from one bit of water to the next and the energy that's carried them so
far doesn't just vanish, wave action is responsible for the erosion of cliffs
and beaches around the world and it can even be harnessed to turn the
relentless up-and-down motion into electricity.
So, the next
time you sit contemplating the surf, spare a thought for the long journey that
the waves have taken and the fearsome storms that have given them life.
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