It is now day 10 of Iceland’s newest eruption of the Fagradalsfjall volcano.
While only 1 fissure vent is still active, a fairly large and elongated spatter cone
has formed along the axis of the original fissure.
This vent which I estimate to be 38 meters or 125 feet in height has continuously erupted
material which flowed to the southwest.
The walls of the elongated spatter cone formed a sort of guiding wall while forces due to
gravity aka the lower terrain to the southwest pulled molten rock in that direction.
It is quite spectacular!
For much of the past week, the eruption site has been closed to tourists, and there are
several scientific reasons behind this.
The simplest one is the location and viewing area possible by the eruption.
During 2021 and 2022, the eruptions of the same volcano occurred in lowlands, and tourists
were directed to view lava from high points only a few hundred meters away.
In contrast, the ongoing eruption has also occurred in lowland but for a fairly long
distance surrounding the eruption site is also lower terrain.
Since the eruption is surrounded by large areas of lower terrain, it means you cannot
approach the eruption site without having the potential to encounter dangerous and even
perhaps lethal levels of several volcanic gasses.
Volcanic eruptions produce fairly large quantities of hydrogen sulfide, sulfur dioxide, and carbon
dioxide.
Only 100 parts per million, that is one ten thousandth of the air needs to be hydrogen
sulfide or sulfur dioxide to be immediately dangerous to human health.
These gasses in high enough concentrations do kill, and I point to an example where invisible
yet heavier than air volcanic gasses from an eruption of Indonesia’s Dieng volcano
in 1979 caused more than 100 fatalities.
Thus, if you want to be relatively safe in my opinion while hiking to the eruption site,
only go along the designated path which I have marked on screen (it is known as “Trail
E”), respect closures of this trail, do not attempt to walk on any lava flows, and
I am also including lava flows from the 2021 and 2022 eruptions in addition to those from
the ongoing eruption, while also watching for signs of various unhealthy volcanic gas
concentrations, with some of those symptoms being shown on screen.
Reason number two is that the dike intrusion which has supplied the last 3 eruptions has
generated more than ten thousand earthquakes which has in my opinion weakened the overlying
crust.
Thus, above the dike, the crust can much more easily fracture and crack than it did in 2021,
and new fissures can develop without warning theoretically a lot more easily.
Thus, people should not go into the approximate region I have outlined on screen due to the
chance a new fissure could form underneath a person in that region.
With all of this being said, the local authorities reopened the hiking path to the eruption on
July 17th, so tourists and locals alike can now once again get somewhat close to the erupting
fissure and advancing lava flows!
Lava has advanced by as much as 1,000 feet a day, following a southern path, and on July
14th the pahoehoe and aa lava flows covered a section of Fagradalsfjall’s 2022 eruption
lava flows!
I currently estimate that the eruption rate has decreased from the initial 70 cubic meters
per second during hour 1 of the eruption to 11 cubic meters per second on July 18th.
As a final note, there is now a chance that the advancing lava flow might be redirected
in a different direction.
As at 4:11 am local time on July 19th, about one third of the existing spatter cone collapsed
in a 15 second event.
Lava then quickly spilled over to the northwest, meaning molten rock could now theoretically
form a dominant new lobe in that direction.
However, in my opinion this breach in the crater wall is most likely to simply get sealed
and lava will continue to flow immediately to the southwest of the erupting vent.
The topography still has the steepest slope going towards the southwest where lava has
been dominantly flowing.
Thanks for watching!
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