Ah nature; the thing that sits outside your window and you don't fully appreciate it until
you go out and explore it for yourself, then the process often repeats itself.
Speaking of processes, how did nature take form?
This is one of the underlying questions that defines the nature of science.
One part of the natural world is the coast.
Water makes up 71% of the Earth’s surface, and is vital to all organisms on Earth.
Despite its magnificent properties in which life could not exist without, water is powerful.
It's obviously powerful on a large scale, with devastating natural disasters claiming
lives and property each and every year.
But on a smaller scale, over the course of thousands and even millions of years, water
has shaped the natural world around us.
The coast refers to the general region of land near the water.
But how did the features we commonly associate with the border between land and water come
to be?
To explore these features, here is the beach in White Rock, British Columbia, Canada.
A beach is where loose material accumulates on the shores of bodies of water.
The shore is the area between high and low tide.
As you can see, the tide is obviously quite in here.
As you can see here as well, the high tide limit is right about here.
It can be seen by the end of wet sand and the dried seaweed.
Also, water drops the heavier material first, hence the separation between large and small
rocks.
But did the loose material just happen to drop here by some magic trick?
No.
For a beach to form, there needs to be a sheltered environment, like a bay.
A bay forms when rock is eroded.
But not just any rock, rock that is relatively soft.
Compared to the rock beside it, the softer rock erodes at a faster rate which recedes
the coastline.
As you can see, White Rock beach is on a bay.
The pieces of land sticking out are called headlands, which are made of harder rock than
the bay.
Another criteria for a beach is that the swash, which is the incoming wave of water, is stronger
than the backwash: the retreating water.
The swash is extremely evident, while the backwash isn’t quite as obvious . On a diagram,
it seems simple enough, but the forces of nature, especially when viewed in real time,
are rarely simple.
Water is a good carrier of loose material, which is exactly what beaches are made of.
If the swash is stronger, the wave is called a constructive wave, but if the backwash is
stronger, it is called a destructive wave.
Since there is a beach here, the waves are constructive.
All you have to do to confirm this is proof by contradiction, when we assume the opposite
is true and look for contradictions.
If we assume the wave is destructive, then there would be no natural beach.
The wind, water, and sediment result in another phenomenon called longshore drift.
As you may have noticed, the wind rarely blows perpendicular to the shore, thus, the swash
comes at an angle.
But regardless of the angle of the swash, the backwash always moves at a 90 degree angle
to the shore.
If this process is repeated over and over, sediment moves along the shore.
This isn’t necessarily obvious, unless it’s what you’re looking for.
So, if the wind is blowing South more than North, as it is here in White Rock, the loose
material moves South.
An interesting feature which arises from longshore drift is a spit.
Basically, a spit forms when longshore drift carries sediment and compiles it into a piece
of land which sticks out into the ocean.
You see that water tower over there?
That was built on a spit, in another country.
Since it is a result of longshore drift, spit formation relies on the wind direction which
influences ocean currents, along with swash and backwash.
It's interesting how I could travel for kilometers in my country, minding my own business, and
nobody has to care, but if I cross this little body of water, again minding my own business,
then suddenly a lot of people start caring.
But, how do things erode?
How do rock and other solids wear away?
Well, firstly there's attrition, which is when rocks strike together..
Abrasion is when they rub together.
This can also happen with sediment, which is easy enough to spot here as the water is
full of sand.
Hydraulic action, in which water is driven into cracks.
Finally, there's corrosion, which is a chemical breakdown.
Usually, erosion isn't noticeable overnight, but it can happen.
Do we sit back and let nature have the last laugh?
Well, yes, we have no system that defends against nature entirely, but we're humans,
so with our intelligence we find ways to slow down natural processes.
To protect against erosion, rocks are placed above the high tide limit.
If you ever go to a beach and see rocks like these, they're not natural.
They're called a riprap.
Now back to our good friend longshore drift.
To protect against longshore drift stripping beaches away, groynes are installed.
Not this type of groyne, but that type of groyne.
Since longshore drift causes sediment to move along a coast in the same direction as the
wind, beaches can lose sand.
To prevent this, groynes are installed to trap the sediment from moving along the beach.
As a result, sand piles up on one side of the groyne, making the boundary between land
and water different on both sides of it.
This storm sewage outflow pipe acts as a groyne.
The sand level on one side is higher than on the other.
Speaking of storm sewage, our inventiveness has caused us to prepare by building storm
sewage outflow pipes which basically remove water from the street during a heavy storm
and return it to the ocean.
On this beach, people have built a dyke, which not only holds the railroad tracks, but prevents
strong waves from making their way onto the street; preventing floods.
The defenses here are adequate.
The people will live.
On the note of strong waves, what is a fascinating characteristic about strong waves?
They break.
Since water travels in columns, the friction of the part near the bottom begins to increase
when approaching shallow waters.
The bottom part slows down, while the top part continues on, causing the wave to become
steeper and steeper until breaking.
If the slope of the ground is too flat or too steep, the wave won’t break.
If there were a tsunami here, the only place to go is up the hill.
Since this is part of a larger metropolitan area, there shouldn’t be a problem with
shelter.
Another interesting thing here is the wildlife, which I got a chance to catch up with.
♪♪♪
We haven’t even considered most of the social aspects of the coast.
Like this bear with a broken nose.
Maybe he got into a fight with a seagull.
Ocean-front real estate is often quite expensive.
Since people like to go to the beach for leisurely purposes, and people are naturally driven
by self-interest, there are many stores and restaurants to accomodate hungry beachgoers
looking for something to eat, and those looking for a treat.
This area also has a rich history.
These railroad tracks which sit upon the dyke used to serve a railroad station to this community,
and continue to facilitate trade between British Columbia and the United States, as well as
passenger trains running along the coast from Vancouver to Seattle and Portland.
The pier was built in 1914 to accommodate a deep-water wharf and tourists.
However, its primary use is for walking and swimming.
The Canadian part of this body of water, called Boundary Bay, is completely separated from
the rest of Canadian waters, which is quite interesting.
The coast, and nature as a whole are remarkable things.
And until next time, thanks for watching.