Redmarked places are the places I made mistakes when recording it.
Earth Science
Listen to part of a lecture
in an earth science class. The class is having a discussing.
Okay, so we say rocks of volcanic. What do we really mean? Linda?
Well, would it come out as hot
and melts of rock, lava from
deep down inside the Earth, and then cool and harden in
the air.
Good, except that it isn’t always the air that cools
the lava into rock.
Oh, the ocean. Isn’t there a lot of volcanic
activity down at the bottom of the ocean? Way out
of the middle, along the … oh, what do you call it?
Daniel?
The middle ocean ridge?
Right.
See,
how do scientists go about studying that?
Well, in the 70’s, they started
mapping the shape of the ocean floor out there with solar. You know how solar works?
Sure, like radar.
Okay.
But solar is sound,
high-frequency sound that a ship sends down.
Well, the scientists on the ship can tell a lot about the ocean bottom by how these pulses of sounds echo back.
That’s good.
Thanks, but I was wandering like, couldn’t they just go down to the ocean floor
in submarines and take a look?
Well, fist, we have to
realize that at this depth, say, 3kms down, the
pressure will be about 3000 times the pressure up the surface.
Oh, so, you are saying the
pressure would crash any submarine out there that tried
to go all the way down to the bottom.
Well, for a long time, that
was the case, and still is, even today for any normal submarine. But eventually,
a few of vey special ones were constructed, with titanium hulks that won’t collapse even at pressures that great. And they have got little windows made of special material that can withstand high pressures,
and video cameras and really powerful lights that the
people inside the sub use to explore the ocean bottom. And after about 4
hours moving around down there, using a battery-power
motor, well, then the submarine releases its weights.
The heavy metal weights that
put it down. And for the next couple of hours,
it’s rising back to the surface, and…
So, what do they end up seeing
down there?
Well, for one thing - these
long ridges running up
and down in the middle of the oceans, they were able to confirm that these were
volcanic, not just the origins. But I mean, the hot lava had flowed up recently, sort of like toothpaste coming out of the tube.
And it’d cooled into the rock formations along the ridge. Oh, and that reminds me of one
dive back in, I think that was 1979. The
submarine went down to explore the middle ocean region of Pacific, and I have
to understand the temperature of the bottom is
normally just about freezing, zero degree
celsius. And they’are down there exploring some very new lava formations. And
they see what it looks like this big, black, sort of
muddy cloud in the water. So they move up close
enough to it that they can use this thermometer on the outside of the submarine. And suddenly, it starts
melting, this thermometer was made to measure the
temperatures over 300
degrees Celsius. It just
melts. And these
guys realized that temperatures like that can
also melt the special windows in their sub. And
they’re almost gone right into the middle of this big, black cloud.
Wow.
Yah, you said that - WOW. So, anyway, since then this things have been found
spreading up all over
along the middle ocean ridges. And now they haven’t
a name. We call them smokers - black smokers. And
then we’ve came to understand that they are part of a really important process, one that regulates the
chemistry of the oceans.
The chemistry? How so?
Well, we know that the
rivers flowing into all
the oceans around the world carry dissolved salts.
So what happens to those salts? They don’t all just stay dissolved
in the water.
No? Then what?
Well, they are cracks in volcanically
active parts of the ocean floor where cold ocean water seeps down
into the rock below. What do you suppose happens
there?
Well, I guess, the water
will cool the hot, volcanic rock down there…
And?
And that would heat up the water a lot!
Right, even super-heated, and then shot
back again. And in theory, over millions of years, all the water in the oceans could’ve circulated down through
the rocky crust, and come back up again super-heated. And in the process, reactions
with the hot lava remove the salt, taking them out of water. So when the water shoots up from the
ocean floor, it leaves behind the salts, and
brings up a hot,
thick, and incredibly rich cloud of minerals drawn out
of the rock that was cooling.
Those ‘black smoker’ they
saw…
Exactly!
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