The little part here is highly metaphorical, or perhaps I should say challenged in regards of prominence. The volcano in question is once more Nishinoshima.
Back in 2013 when it rumbled back to life it was all the rave, but nowadays I bet that even most volcano afficionados have missed the return of the ocean beast.
A short recapitulation
Prior to 1973 poor Nishinoshima was a deeply misunderstood minute island in the Volcano Islands Group along the Ogasawara chain. Not so strange since the larger southern brother in the Volcano Islands is none other than Iwo Jima.
The misunderstanding part comes from someone stating that it had not erupted for 10 000 years. I have now spent 7 years trying to find a reliable source for that dating, by now I am quite comfortable stating that it is either a mistake, failed translation, or just simply a factoid out of someone’s butt.
Nishinoshima is normally rated as a stratovolcano, rising 3 000 metres from the ocean floor, occupying around 600 square kilometres at the base. It has a 1 in 10 gradients on all sides except towards the Ogasawara Through where it is far steeper.
It is believed that the Ogasawara Through is the main driving force of the volcanism in the Volcanic Islands, problem is that it is still argued about exactly what the Ogasawara Through is. I have seen articles stating that it is an arc/back arc setting, or a spreading centre Graben, I even found a rather dubious source stating that it is a plume track (that we can probably rule out though).
The sub-aerial part of Nishinoshima in early 1973 consisted of a small island and a few rocks poking up along the north-eastern end of a 1.2-kilometre-wide caldera. The caldera was by this time almost filled in; it was only 107 metres deep at the deepest point.
The Ogasawara Through runs in a NNW/SSE direction with Nishinoshima perched precariously on the western shear-wall.
Whatever had happened to the tip of the original Nishinoshima volcano, it seems like it may have meandered down in a generally easterly direction, and that it was slowly building up below surface until the 1911 survey.
The eruptive history
On the 30th of May in 1973 an island forming eruption started that lasted until sometime after the 1st of May in 1974. This left a flimsy island that was later joined with the old Nishinoshima by wave action.
In January 2000 a minor sub-marine eruption filled in portions of the caldera, setting the stage for the later rapid Island growth, the stage was now set for the current set of eruptions.
The 2013 eruption sequence
On the 20th of November in 2013 an eruption was noticed about south-east of the old island. In early December a new island had formed, and on the 26th of December the old and the new islands merged into an ever-expanding eruptive island.
As the eruption ended on the 14th of February 2017 researchers descended on the island to study how life would return to the island, there was much rejoicing among them. By now the island was 2.3 square kilometres.
Apparently, scientist feet are irritating to large volcanoes, so on the 17th of April 2017 the island resumed explosive eruptions, laying waste to the equipment left behind. This eruption was over on 3rd of October 2017, leaving the island at 2.9 square kilometres.
No doubt researchers started to rejoice again as they planed a new mission to the island, but it seems that they where to slow, and Nishinoshima resumed eruptions between the 12th of June 2018 until the 31st of October the same year.
By now the scientists had stopped rejoicing, observing that observational flights were probably a good idea for the foreseeable future. It was perhaps a wise choice.
The current eruption
Any normal volcano would by now have relaxed and opened a beer, patted itself on its back after a work well done, and invited in the by-now frustrated scientists. After all, every eruption in the sequence that started in 2013 had been smaller and smaller, a sure sign that things should be winding down.
It turned out that Nishinoshima was not a normal run of the mill volcano. On the 6th of December 2019 it rumbled back into life in what in raw lava volume is equal to the entire first eruption.
So far, the still ongoing eruption has increased the size by 30 percent to 3.8 square kilometres, not a mean feat since it by now is growing outside the original caldera at ever greater depths.
What is the not so good part of this, is that the island expansion has hit the precipice of the Ogasawara Through, as evidenced by the straight line that is forming on the east side of the island. Any further growth in this direction would take rather stupendous volumes to build up the shear-wall of the Graben.
The Future of Nishinoshima
By now it is probably safe to assume that Nishinoshima is a far more serious volcano than previously believed. There is a distinct chance that the volcano will continue to erupt with interludes ranging from months, via years, to a few decades for the foreseeable future.
The growth will be along the northern and southern coasts, since there are marked ridges going in these directions, to a lesser extent it can continue to grow on the western side even though the depth curve is steeper on this side.
So, if all goes well, we will end up with an elongated island out in the ocean, life and rejoicing scientists will start to sprout forth, and people of a somewhat Swedish nature with a sailing boat will plan to go there.
There is though a threat to this glorified future of palm trees, happy birds, rejoicing scientists and mad Swedes.
The threat is simple, there is after all a minor risk that a large portion of Nishinoshima will slide off into the steep sided Ogasawara Through, opening the magma chamber, causing a volcanic tsunami cum Krakatau racing towards the Hawaiian Islands.
The only thing we can do about is arming the island with equipment and via remote sensors monitor it, giving advance warning about any upcoming craziness. As usual, science is there to save lives, regardless of if the scientists are rejoicing or not while doing it.