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In the pacific ocean is a region that has been almost impossible
to study. A region so dangerous, for many years,
scientists didn’t dare venture there . A place with nearly continuous volcanic eruptions.
Kavachi Volcano in the Solomon Islands is one of the most active underwater volcanoes in the world.
It sits just 20 meters below the surface - and
its base lies on the seafloor at a depth of 1.2 kilometers.
Beyond this, little was known about this volcano for the centuries it’s been known
to exist. That is, until 2015, when a rare lull in volcanic activity allowed
researchers to get close to its active crater and flanks for the first time.
Using a combination of underwater cameras, recording devices, and scuba divers, the team
collected a huge amount of information–even though it meant taking a few risks.
Although the volcano wasn’t actively erupting, gas still bubbled wildly from around the rim,
which could cause caustic burns if the divers got too close. The team
had to listen carefully to the water for the telltale rumble that comes
along with eruptions–just in case Kavachi suddenly unleashed its fury once more.
But what they found was worth the danger. Not only did they get bacterial and rock samples,
but their baited cameras also captured some incredible sights. There were zooplankton and
larvae as the scientists expected—but also, something completely surprising.
Schools of fish like bluefin trevally and snapper,
silky sharks and hammerhead sharks were all seen inside the crater.
The water temperature above the crater was more than 13 degrees C higher than
the surrounding ocean, growing as warm as 29 degrees C. What’s more,
the hydrothermal vents were still releasing concentrated amounts of carbon dioxide
and sulfur dioxide, which makes the water much more acidic than normal.
Yet this vast array of lifeforms was still living in and around the mouth
of the volcano. It’s almost as perplexing as someone deciding to build a house on
top of an active volcano just a few months after the lava has solidified.
How were these creatures all surviving such an inhospitable environment? And
what can such extreme creatures tell us about the future of our oceans?
Kavachi is a fascinating example of submarine volcanoes, but it’s only a tiny window into a
vast underwater realm. Of Earth’s 1,500 active volcanoes, the majority are found in the ocean.
Some are the result of plate tectonics– plates pulling apart, or smashing into each other.
Other volcanoes come from hot spots, which form not from tectonic plates,
but from abnormally hot areas of magma that burst through, usually forming islands.
And volcanoes are only a small part of the geothermal activity happening on the seafloor.
There are also hydrothermal vents, which form when water seeps into the broken crust,
gets superheated up to 400°C, and shoots back into the ocean filled with chemicals and minerals.
Cold seeps occur in similarly volcanic places,
but the water doesn’t heat up. Instead, sulfide, methane,
hydrogen and hydrocarbon-rich fluids leak into the ocean, often for longer than hydrothermal vents.
Then there are megaplumes, which are like hydrothermal vents on steroids.
These brief but enormous bursts of hot, mineral-rich water are still baffling to
scientists, because they’re so hard to observe. But it’s clear that they have immense consequences
for surrounding ocean water chemistry, since a single megaplume can discharge more than 100 cubic
kilometers of water in one go–the equivalent of 40 million Olympic-sized swimming pools.
As for Kavachi – It is located on the Pacific tectonic plate only 30 km northeast of the
boundary with the Australian plate. It’s released huge quantities of steam, ash, and glowing bombs
of lava on multiple occasions. It has even produced ephemeral islands up to a kilometer
long over the course of its explosive activity, making it a very dangerous object of study.
All this volcanic activity in Earth’s oceans has had an enormous impact on the seafloor.
Even long-extinct volcanoes have left traces on the underwater topography.
The rugged hills and mountains created by volcanic activity are called seamounts,
and they cover more than 28.8 million square kilometers —an area larger than
any terrestrial habitat. Some of them are in the deepest,
darkest parts of the ocean, while others come all the way up to warm shallow seas.
Scientists think around 45,000 seamounts exist all over the world,
but we’ve explored fewer than 200 of them. In other words,
we’ve seen less than one percent of what might be some of the most unique habitats on our planet.
While researchers stumbled upon the first seamount back in the late 1800s, it wasn’t until the 1970s
that we first saw hydrothermal vents—and the bizarre creatures living around them.
In 1977, a team of 30 geochemists, geophysicists, and marine geologists
came together to study the Galapagos Rift, 400 miles off the coast of South America. No marine
biologists were included because everyone assumed there would be no life to see.
As they dropped cameras down 2,500 meters below the surface,
the researchers were surprised to see what looked like signs of heat. And then, to their shock,
something even more unexpected came into view - what looked like alien lifeforms.
Foot-long pale crabs. Red-headed tube worms the size of a full-grown human,
clustered tightly around steaming pillars. [6] They had discovered hydrothermal vents,
and the baffling ecosystem they support.
From that point on, scientists employed a vast array of technologies to continue exploring these
underwater geysers. There’s the Lost City Hydrothermal Field in the Atlantic Ocean,
whose vent structures grow as tall as the Leaning Tower of Pisa (which is 55.8m) and
come from peridotite rock instead of basaltic rock, which makes up most of the ocean floor.
This means the chemicals coming out of the vents around the Lost City have a
much different composition than in other locations—and yet they still support life.
In fact, scientists have found around 800 vent animal species and countless microbial species,
with many more likely to be discovered as we continue exploring the deep ocean.
In addition to the tube worms and crabs scientists first saw in the 70s,
we now know there are giant mussels, shrimp, and, perhaps the most important organisms of all,
microbes, that survive alongside the vents. These microbes make up the entire base of this
strange food chain. And they do it in a place where there’s no sunlight for photosynthesis.
Instead, the microbes convert inorganic compounds like hydrogen gas, sulfur,
methane or iron into nutrients. This allows the microbes to thrive in what would otherwise
seem like hellish environments—and support many other organisms as well.
These microbes help explain the surprising amount
of life around Kavachi. The researchers found bacteria related to Sulfurimonas,
which use chemosynthesis on sulfur and CO2 to produce energy. Filter feeders like krill
and clams can survive entirely on these bacteria, and those populations in turn
can support bigger fish and even sharks. It’s all part of a vast, volcano-based food web.
And it happens all around the ocean in different environments.
Take the giant red-tipped tubeworms for example. They have no mouths or digestive tract,
instead relying on chemosynthetic microbes hosted inside their body to provide them with energy. [7]
Or there’s the vent shrimp, which has a symbiotic relationship with chemosynthetic bacteria living
in its gill chambers. It seems that the shrimp get some kind of nutrients from the bacteria,
and the bacteria benefit from the shrimp being able to get close
to the vent systems where the highest quantities of chemicals are pouring out.
And the life forms populating these volcanic settings don’t stop there.
Around Kick’em Jenny, the most active submarine volcano in the Lesser Antilles of the Caribbean,
researchers found what they believe to be the largest mussel shell ever sampled. One
Bathymodiolus boomerang measured 36.6 cm long—bigger than a footlong sub.
Near one seamount in Samoa, a growing volcanic cone named Nafanua supports a
thriving population of eels around its summit vent. They feed on shrimp and seem capable
of surviving the hydrothermal emissions, even though other fish are killed by them.
And that is one very big problem with all these volcanically active
sites—there’s a big risk of getting burned, poisoned, or caught up in an explosion.
While most of the seamounts around the world are made from extinct volcanoes,
there are still hundreds of active volcanoes erupting on a regular
basis. And when those eruptions happen, they can be disastrous for marine life.
In 2011 for example, a submarine volcano near the island of El Hierro triggered more than
10,000 earthquakes on land and led to vast numbers of dead fish floating on the ocean surface.
The ocean temperature increased nearly 19 degrees C around the volcano crater,
carbon dioxide caused the water to be much more acidic, and in some areas,
the water was almost completely void of dissolved oxygen.
The debris created by the eruptions also made the water much cloudier than normal. Scientists found
that the upper limit of light penetration was 100 meters shallower than normal, which
can have a big effect on plankton communities and other organisms living in the mesopelagic.
In other cases, submarine volcanoes unleashing gouts of lava have killed deep sea fish,
which then float to the surface, sometimes teaching us about fish
we never new existed. But it means that even those organisms that may be benefitting from
hydrothermal vents can be killed if the volcanoes become more eruptive.
And if there’s enough volcanic activity happening all at once,
it can have profound consequences on ocean life.
Researchers point to the Cenomanian-Turonian event that happened around 90 million years
ago and led to the extinction of almost a third of marine invertebrate species.
That sudden collapse of ocean life is thought to be largely the result
of high levels of hydrothermal activity making the ocean too warm and acidic.
That said, huge eruptions can have a positive effect on phytoplankton populations.
Just this year, the largest submarine eruption of the past century occurred in the South Pacific
Ocean. The Hunga Tonga volcano erupted in January and was so massive that its plume
of ash reached 58 km in altitude. The blast was so loud that it could be heard in Alaska,
nearly 10,000 km away, and it triggered a massive tsunami wave.
But that enormous eruption also triggered a huge phytoplankton bloom that could be seen
by satellites. Scientists have hypothesized that these oxygen-producing microbes had a
sudden boom because of the ash and nutrients released by the volcano.
Clearly the effects of underwater volcanism are a mixed bag for ocean life. Which raises
the question of how the sharks and fish swimming around Kavachi are able
to deal with the chemical changes to the water, and the threat of another eruption.
And it’s still an open question. There are a lot of logistical challenges for researchers trying to
get out to such remote locations, let alone avoid having an eruption occur right underneath them.
But these issues are well worth researching, because they could tell us a lot about how
marine life will respond to climate change. As more carbon dioxide enters the atmosphere,
the oceans will become more acidic, affecting shell builders and other invertebrates.
And as the temperatures rise, marine heat waves are becoming more common
and threatening coral reefs as well as fish. So the better we understand how
life survives around hydrothermal vents and underwater volcanoes,
the more we might be able to do to protect threatened species and help them adapt.
And maybe we’ll even uncover a few more shark-canoes along the way.
My mission with these videos is to inspire people to love the natural
world, and to show that through methodical science, we can improve the state of things.
We all get a constant stream of the “everything is doomed” narrative - but I actually think the
opposite is true. Not that terrible things aren’t happening, but that we as a species are at last
in a position to make meaningful changes. We can learn how creatures react to a changing climate,
and find ways to change policy around that. We can learn how to create more sustainable energy. We
can learn how to protect ourselves from terrible diseases with vaccines, how to improve the lives
of children around the world by making sure they have something as simple as the right vitamins.
But like with many things, the science only goes so far.
How can we actually implement the changes that need to happen?
Donating money is one way - and we often get pushed to donate to various causes at
this time of year - rounding to the nearest dollar at the grocery store,
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