- [Ross Parnell-Turner] And in these places where we have
these hydrothermal vents, it's like an oasis of life
because you have these vent systems
that bring hot water at high temperatures,
couple 100 degrees that are also full of all
kinds of nutrients, like iron and sulfur and calcium.
And that means that life can thrive.
Bad news is every few years,
the whole place gets totally destroyed
by a volcanic eruption.
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- [Kate Furby] Welcome to wavelengths
where we talk about our planet with experts
from Scripps Institution of Oceanography,
covering everything from the deep sea
to the edge of the atmosphere.
I'm Kate Furby, a marine biologist and journalist.
I got my PhD here a few years ago,
and now I'm back learning more about
what's happening at Scripps.
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I'm here with Dr. Ross Parnell-Turner,
a marine geophysicist.
Thanks so much for joining us today.
I'm really excited to talk about underwater volcanoes.
I was wondering if we could start
with you setting the scene?
We're actually here right next to the ocean.
Can you give us an idea of what the ocean floor
looks like here in San Diego?
- So the ocean floor here you might
think of as being completely flat,
but actually if we take all the water away
and look down there, it's actually got a lot of steep slopes
and a lot of interesting topography.
And right here off the coast of San Diego,
we have a very deep series of canyons that go hundreds
of feet deep under the water.
So it's definitely not flat.
- Which part of that do you study?
- [Ross Parnell-Turner] So I study the part
in the middle of the oceans,
where the tectonic plates are spreading apart
and are creating new ocean floor.
- So that's what we call seafloor spreading?
- Exactly.
- Is like the two plates moving apart.
- Exactly.
You can kind of think of it as like
a pair of plates that are spreading apart
and having a new pile of crust being formed
at the point where they break apart.
- Is there a pie analogy?
Can we do a pie analogy?
- There isn't really a pie analogy.
(laughs)
- Okay, can you tell us what is this?
- In the middle of the seafloor spreading,
we have these things called hydrothermal vents
which have very hot water that's full of all
kinds of nutrients and minerals that are really useful
for animals to thrive,
and this is the case from a creature called a tube worm,
but originally it would have been about two meters long
and it would have been straight
and maybe an inch in diameter.
- So these are pretty dynamic places,
that are just sort of periodically
getting paved over by lava
and then I assume sort of sprouting up
in a new location?
- Exactly, yeah.
So these tube worms reproduce by generating larvae
and lots of creatures down there have a larval cycle.
And so after an eruption,
those larvae can recolonize the seafloor.
- Cool.
- So it's amazing how quickly life can come back.
- What causes the volcanic eruption?
- [Ross Parnell-Turner] So here's the earth
and one kilometer underneath
the seafloor is a magma chamber
that is slowly filling up,
and above that,
you have seen water percolating down and heating up.
It gets so hot that it zooms back
up through these deep vents and those
are the hydrothermal vents that you see on the seafloor.
And this is where we see all the life.
There's tube worms and crabs and octopuses down there.
And this area is warm,
it's full of nutrients,
and it's a great place to live.
However, in every once in a while,
the magma erupts, flooding molten lava
out of the crack between the two plates
making it not such a good place to live.
So this is what we look for on our expeditions.
We have an underwater robot that we use
to put instruments into the vents to measure
the temperature and the chemistry of the water,
so we can sense that the volcano is going to erupt soon.
- You're gonna take a little robot
and sort of send it into this deep crack in the ocean
to try to discover more about how the earth is formed.
- [Ross Parnell-Turner] That's exactly right.
- What are you hoping to find?
- So we're hoping to find evidence.
The volcanic system is getting ready to erupt,
and we're hoping that it's going to erupt
in the next couple of years,
so that we can take a really close look at what happens
when a seafloor eruption happens.
- So we've been standing in front of this biggest map
I've ever seen for a little bit now.
Can you tell me what we're looking at here?
- So we're looking at a map of the seafloor
that's actually a sonar image that was created
by this underwater robot called century
that we use to map the seafloor.
And this map is our study area.
The area that has erupted in the past
are all these black splodges you can see on the map
and the main area where the two plates are spreading apart
is this line that goes up here,
which is called the axial volcanic trough,
and in terms of distance,
the span across this valley is a couple of 100 meters,
which is about the same size as Scripps Pier,
which is just out there.
- Why is this important?
- So it's important because if you think
about our planet, 60% of it is covered by the oceans
and we still don't really understand how the bottom
of the oceans like how the seafloor is created,
and in places like this,
we can actually observe that process
of seafloor creation in real time or near enough real time,
and so it helps us understand things like
how these eruptions work,
but also how it affects the creatures
that live on the seafloor.
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