In January of 2020, a magmatic intrusion began in Iceland just southwest of the Blue Lagoon.
After the ground was uplifted by several centimeters, the intrusion stopped without resulting in
a new eruption.
Then, two months later another intrusion occurred in essentially the same spot.
And in June, a 3rd magmatic intrusion began to the northeast of the two prior locations.
Although not known at the time, what had just been witnessed was the beginning of a new
eruptive period on the Reykjanes peninsula.
As of September of 2022 it has led to 7 magmatic intrusions and 2 spectacular volcanic eruptions.
Both of these eruptions occurred adjacent to an old subglacial feature known as Fagradalsfjall.
The eruptions each consisted of gentle lava effusion which originated from an underlying
fissure.
It was initially thought that both of these eruptions occurred from within the Krysuvik
volcanic complex, which is a loosely defined assortment of fissures and crater rows which
cover an area of 350 square kilometers on the peninsula.
However, something was a bit off.
Past fissures within the Krysuvik complex have generally trended to the northeast at
an angle of between 45 and 55 degrees.
Yet, the 2021 Geldingadalir eruption produced a fissure which trended to the northeast at
an angle of 62 degrees.
On its own, this might not seem like too large a difference, but this was quite peculiar
given the nature of past eruptions of the Krysuvik complex.
Then, when the 2022 Meradalir eruption occurred, the eruptive fissure had an angle of 79 degrees.
This suggested that these two eruptions might not have originated from within the Krysuvik
complex.
Looking around Fagradalsfjall, there are more fissures which have a similar steep angle
which don't match those found in either of the adjacent volcanic complexes.
Through this and other evidence only made possible by the two recent eruptions, and
important discovery was made.
The 2021 Geldingadalir and 2022 Meradalir eruptions originated from a completely separate
volcanic complex known as Fagradalsfjall.
Thus, in September of 2022, Icelandic volcanologists along with the Smithsonian Global Volcanism
Program added Fagradalsfjall to what was before a list of 34 volcanoes but is now a list of
35 volcanoes within the country.
A new volcano had been born, splitting what was formerly the single Krysuvik complex into
2 volcanoes!
This new complex was defined as being 16 kilometers long and 5 kilometers wide, representing by
far the smallest true volcanic area on the peninsula.
It stretches from just east of Grindavik, representing its southernmost point to Keilir,
its northernmost point.
However, the vast majority of this volcanic complex is located on and around the subglacial
volcanic feature which is how it got its name, Fagradalsfjall.
This might seem like a pointless nomenclature change but the designation is quite important
in better understanding future volcanic threats on the peninsula.
For example, in the Krysuvik volcanic system the average eruption since the end of the
last ice age has had a degree of explosiveness to it, with 7 out of 11 total recent eruptions
rating on the volcanic explosivity index as a 1 or a 2.
Yet, evidence seems to suggest that eruptions at Fagradalsfjall are far less explosive,
as shown by the two recent eruptions which occurred which both rated on the volcanic
explosivity index as a 0.
Another important detail which differs between the two volcanoes relates to how long individual
fissures produced during eruptions can be.
In Krysuvik, some fissures are as long as 5,000 meters in length.
In comparison, fissures within the newly designated Fagradalsfjall complex appear to be less than
2,500 meters in length.
So, what does all of this mean other than simply designating a new volcano?
Simply put, magmatic intrusions have not been occurring in the Krysuvik complex but rather
in Fagradalsfjall.
This means that the area surrounding the mountain is likely to see more potential eruptions
in the future instead of the Krysuvik complex unless another major change occurs within
the peninsula.
After all, magmatic intrusions have so far occurred in 2 of the 5 complexes, and during
past eruptive periods as many of 3 of these have erupted in rapid succession after a single
eruption occurred.
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