Volcanoes are a sight to behold from a safe distance, as they could be deadly!
Many people have seen the footage or images of
volcanoes but may not know that there are volcanic eruptions underwater!
What does an underwater volcano look like, what
causes it, and can they affect you on land?
In this video, we bring you terrifying discoveries scientists have made about underwater
supervolcanoes!
Few things are as awe-inspiring as a volcanic eruption!
They can't even be stopped or prevented!
But what is a volcano, and how does a volcano erupt?
Let's dive into a bit of interesting geography!
Many mountains form by folding, faulting, uplifting, and erosion of the Earth's crust.
Volcanic terrain, however, is built by the slow accumulation of erupted lava.
The vent may be visible as a small bowl-shaped depression
at the summit of a cone or shield- shaped mountain.
Through a series of cracks within and beneath the volcano, the vent
connects to one or more linked storage areas of molten or partially molten rock or
magma.
This connection to fresh magma allows the volcano to erupt repeatedly in the
same location.
In this way, the volcano grows ever larger until it is no longer stable.
Pieces of the volcano collapse as rock falls or as landslides.
When molten rock below the surface of the Earth rises through volcanic vents, it is
known as magma.
However, after erupting from a volcano, it becomes lava.
Magma is made of molten rock, crystals, and dissolved
gas; picture an unopened bottle of soda with grains of sand inside.
The molten rock is made of the chemicals oxygen, silicon,
aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese.
After cooling, liquid magma may form crystals of various minerals until it becomes solid
and forms igneous or magmatic rock.
Originating many tens of miles beneath the ground, magma is lighter than surrounding
solid rock.
It is driven towards Earth's surface by buoyancy; it is lighter than the
surrounding rock and by pressure from gas within it.
Magma forces its way upward and may ultimately break through weak areas in
the Earth's crust.
If so, an eruption begins.
Magma can erupt in several ways.
Sometimes molten rock pours from the vent as fluid
lava flows.
It can also shoot violently into the air as dense clouds of rock shards, or
tephra, and gas.
Larger fragments fall back around the vent, and tephra clouds may
move down the volcano's slope under the force of gravity.
Ash, tiny pieces of tephra the thickness of a strand of hair, maybe carried
by the wind only to fall to the ground many miles away.
The smallest ash particles may be erupted miles into the sky and are
carried many times worldwide by winds high in the atmosphere before they fall to the
ground.
So, how many volcanoes are there?
The US Geological Survey, USGS tracks over 160
active and potentially active volcanoes in the United States alone.
There are about 1,350 potentially active volcanoes worldwide.
About 500 of these have erupted in the past 100 years!
Many of these are located around the Pacific Ocean in what is known
as the "Ring of Fire."
However, there is a type of volcano not included in the numbers above.
It is an underwater volcano.
You may not know about these underwater volcanoes because
they usually happen far away!
But that does not make them any less dangerous!
In fact, most volcanic activities happen beneath the
ocean!
Two-thirds of all volcanic activity occurs in the deep sea!
So how does an underwater volcano form?
Actually, there is no difference in the formation of submarine or underwater and subaerial
or on-land volcanoes.
Underwater volcanoes also form when molten rock is produced
in the second layer of the Earth's interior and makes its way through the crust.
As Tamsin Mather, a volcanologist and professor of earth sciences at the University of
Oxford, puts it, most submarine volcanism is associated with the continuously active
volcanism along mid-ocean ridges, where two tectonic plates are pulling apart.
The collision of two plates can also cause a volcano.
If both tectonic plates are beneath the ocean, then the volcano will develop underwater,
said Helo.
Over time, they may grow to form volcanic islands, he added.
Volcanic activity within a single tectonic plate can
also result in the formation of a volcano.
This can happen when a hotspot is underneath an oceanic plate, creating a chain of volcanic
islands like Hawaii.
You are probably wondering what happens when a volcano erupts underwater.
The impact of an underwater volcano eruption depends
on its proximity to the water's surface.
If the eruption happens at very great depths underwater, then the weight of the
overlying water acts as a pressure cap.
For example, if a piece of molten rock enters the sea two kilometers or 1.24 miles below
the surface, it will come into contact with cold seawater and cool very quickly.
The water will get very hot, but it won't turn into
steam!
The story is different if the water is shallow enough!
The magma starts to heat the water, which is then converted into steam,
creating a big volume change.
Steam explosions are really destructive because
a small volume of water turns into a huge volume of steam!
Aside from the risk of tsunamis, the mass of ash ejected into the air when an
underwater volcano erupts in shallow water can seriously impact people's health!
The falling ash and emitted gases not only pollute
the air but can affect access to electricity and water supplies!
Because they are underwater, submarine volcanoes are challenging to study.
Due to their inherent inaccessibility, only a few
active sites have been studied in detail.
However, scientists working on land can learn about the history of a volcano by visiting
the volcano site and gathering data.
This can be done using cliff sequences or digging
holes and collecting materials.
For underwater volcanoes, scientists usually have to rely on marine surveys and
mapping technology like sonar.
There have been remarkable underwater volcanic eruptions, and we will dwell on their
powerful impact next!
Let's look at the most powerful underwater volcano ever recorded!
In 2018, the largest active underwater eruption ever recorded birthed a giant,
skyscraper-size underwater volcano!
The insane thing about the eruption is that scientists are still making discoveries about
it!
What have they discovered?
Scientists discovered the 2,690-foot or 820 meters tall volcano in the western Indian
Ocean, off Madagascar, following a puzzling spate of earthquakes that struck near what
is usually a seismically quiet area.
After gathering geological data, including information
from a 2019 underwater survey of the region, the team realized that there was a new
submarine volcano about 1.5 times the height of New York's One World Trade Center!
What's more, this new volcano draws from the deepest volcanic magma reservoir
known to scientists!
According to lead researcher Nathalie Feuillet, a marine geoscientist at the Paris
Institute of Earth Physics, IPGP at the University of Paris, the source of the magma, that
is, the reservoir, is very deep, about 34 miles or 55 kilometers underground!
It was the first time in volcanology that they could
see such a deep reservoir at the base of the lithosphere, the outer shell of Earth that
includes the upper mantle and crust.
Between May 2018 and May 2021, more than 11,000 detectable earthquakes shook
Mayotte, a small island and French territory between Madagascar and Mozambique.
The most powerful earthquake was a magnitude 5.9, but there were also strange
seismic hums, or very-low-frequency earthquakes, that originated deep underground;
they couldn't be felt at the surface but were picked up by seismometers around the
world.
These very low-frequency earthquakes are associated with volcanic activity.
This sudden seismic activity was surprising, given that only two earthquakes have been
detected near Mayotte since 1972 and, until now, the most recent volcanic was left at
least 4,000 years ago.
In July 2018, scientists were stunned when they discovered that Mayotte was moving
eastward at about 7.8 inches or 20 centimeters a year, as detected through GPS data.
At that point in time, the island had only three or four GPS stations, so scientists
installed global navigation satellite systems and ocean-bottom seismometers around the
island to learn more about the geological changes occurring there.
The findings were extraordinary; the combined land and ocean-bottom
seismometers picked up 17,000 events between February and May 2019!
To learn more about the underwater volcano, Feuillet, and her colleagues went on a
voyage aboard a research vessel.
The team knew there had been a magmatic event east of Mayotte, but they weren't sure if
the magma had stayed deep under the crust or
if it had erupted onto the seafloor.
Feuillet reported they put in place a protocol to analyze the seismic signals recorded by
the OBS or ocean-bottom seismometers.
The teams operated around the clock, broken down into shifts, and in less than two weeks,
they could precisely locate the nearly 800 largest earthquakes of magnitudes between
3.5 and 4.9.
For the most part, these earthquakes were found in an area relatively
close to the island, about 10 km or 6 miles from the island's east coast, but were deep,
between 20 and 50 km or 12 to 31 miles deep.
The volume of material that this volcano spawned is 30 to 1,000 times larger than other
documented deep-sea eruptions!
It's more than three times larger than the 2012 Havre
eruption in New Zealand and 2.5 times larger than the 2014 Bardarbunga eruption in
Iceland, Iceland's largest eruption in the past 200 years!
The team is monitoring the region for more earthquakes and volcanic activity.
Let's hear what you think of underwater volcanoes in the comment section below