In the Caribbean, there are 16 active or potentially active volcanoes. These include Pelee
on Martinique, La Soufriere on Saint Vincent, and Qualibou on Saint Lucia. However, none of
these volcanoes have been as active in the last century as the topic of this video. Located 8.5
kilometers north of the northern tip of Grenada in the Caribbean Sea is a primarily submarine volcano
called Kick 'em Jenny. This weirdly named volcano has erupted 14 times since 1939, the most recent
of which occurred in March of 2017. Today, Kick 'em Jenny is at a raised alert status but is not
actively erupting. This video will discuss this volcano, and mention what its future hazards are.
Despite popular belief, Kick em Jenny is not strictly a submarine volcano.
To the east of this vent are a chain of several islands. These islands are all volcanic in origin,
and were formed from the same volcanic complex of which Kick 'em Jenny represents merely the
most recent vent to have erupted. We aren't exactly sure when Kick em Jenny began
to form, but what we do know is that this now underwater vent used to be more than 100 meters
above the ocean surface. The exact dimensions of this former island are unknown, but it was likely
more than 2 kilometers long. This island formed through 100,000 years of intermittent eruptions,
which built the volcano starting at a depth of 1300 meters underneath the ocean surface. Then, at
some point within the last 20,000 years, a massive eruption occurred. This eruption caused the west
side of the volcanic edifice to collapse into the ocean, thus destroyed the existing island.
After the eruption had ended, what remained was a several kilometer wide horseshoe shaped crater
several hundred meters beneath the surface. Over the next several thousand years, a half dozen
other vents erupted large volumes of magma in scattered locations around the volcanic complex.
One of these vents erupted a viscous lava dome, much like what was seen during the early stages
of La Soufriere's current eruption. This lava flow eventually reached the ocean surface, and
created a dome shaped island called Diamond Rock. During the next phase of activity, two eruptive
centers built Ile de Ronde, while a third formed a submarine volcanic cone known as Kick 'em Jack.
Then, 1000 years ago, a large volcanic vent erupted just beneath the ocean surface. Due to the
large volume of lava it ejected, it built a small island called Ile de Caille out of a black colored
volcanic rock called basalt. (pause 2 seconds) However, until 1939, the residents of Grenada
were completely unaware that a volcano existed here. Then, on July 24th of 1939, a volcanic
eruption broke the ocean surface. During a series of explosions, it ejected volcanic bombs, ash,
and steam to a height of 275 meters. The largest of these explosions created a series of 2 meter
tall tsunamis, which then traveled to several region islands. This eruption which had just
taken place, although impressive, was only rated on the volcanic explosivity index scale as a 1.
Over the next 50 years, 9 additional eruptions occurred.
All of these were an order of magnitude smaller than the eruption in 1939.
Only two of these eruptions reached the ocean surface, creating patches of water discoloration.
The reason we are aware of the other eruptions is underwater volcanic eruptions make a very specific
sound and are associated with a swarm of earthquakes. If both of these are detected,
then a small eruption has occurred. The most recent eruption was detected via
instruments on March 29th, 2017. On average, Kick 'em Jenny erupts
about once every 6 to 7 years. As a result, it will not be long until it erupts again.
During an eruption that breaches the ocean surface, the populations of several small regional
islands would need to be evacuated. In addition to the threat of small tsunamis, boulder sized bombs
of lava could be thrown up to 5 kilometers and land on one or more of these islands.
Additionally, non scientific ships should not come close to the active vent of Kick em Jenny.
It regularly vents large amounts of volcanic gas, which thus lowers the density of water and creates
a sinking hazard. In summary, the only hazard which residents on the main island of Grenada
could face are up to 5 meter tall tsunamis generated during unusually large eruptions.
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