The summit of the towering Lascar stratovolcano in Chile rises to a height of more than 18,000
feet or 5,500 meters.
There, are a series of distinct summit craters which have altogether produced numerous recent
volcanic eruptions, marking Lascar as the most active volcano in northern Chile since
historical record keeping began.
On January 30th of 2023, a new distinct eruption of the volcano began, as a presumably high
silica body of lava erupted onto its recently active crater floor.
By two days later, an approximately 88.1 meter or 289 foot long and 30 meter or 98.4 foot
high lava dome had been constructed which had a mostly spherical shape, at least from
a top down view.
Given its size, it suggests that 1.04 cubic meters of lava is being effused onto the crater
floor each second which will continue to increase the size and volume of the dome.
While this may not seem all that exciting, its existence almost guarantees that a powerful
explosive eruption will eventually occur.
For context, the Lascar volcano had until January 30th of 2023, not produced a lava
flow via a lava dome in approximately 30 years.
Yet, it had erupted several times since 1993.
The concern is that this lava dome will eventually become so large that it will act as a successful
cap which will cause gas and pressure to build under it.
This then might eventually become so highly pressurized that it explodes upwards, creating
a powerful explosive eruption which destroys much of the dome.
However, this process can take quite a lengthy period of time.
For example, during the 2020 to 2021 eruption of the La Soufriere volcano on the island
of Saint Vincent, the lava dome was destroyed a little more than 3 months after it began
growing.
Or, at the Lascar volcano a lava dome was emplaced in late April of 1993 and would go
on to be destroyed by a vulcanian eruption on December 17th of 1993, approximately 8
months later.
While the current growing lava dome could theoretically remain without exploding in
the current eruption, it is most likely to get destroyed in some eventual explosive eruption
or eruptions which is the reason for the 10 kilometer or slightly more than 6 mile exclusion
zone around Lascar's active crater.
The 10 kilometer exclusion zone also represents the maximum distance a pyroclastic flow traveled
from the volcano's summit in 1993, per Sernageomin.
While pyroclastic flows generated by the likely eventual destruction of the lava dome might
not reach this distance away, the existing 10 kilometer radius represents a generally
good starting point for hazard modelling.
With this being said, due to the topography of the surrounding landscape, any large overflow
of the lava dome or generated pyroclastic flows which travel beyond the summit crater
region are most likely to travel to the northwest then west although they could also travel
in other directions.
Although it is almost impossible to predict the long term future of a volcano's eruptive
sequence, there is currently not a reason to suspect that any explosion of the lava
dome would create a 1993 sized eruption which was assigned a volcanic explosivity index
rating of a 4.
Of course, things could rapidly change but it in my opinion is most likely that the lava
dome will continue to grow at Lascar for at a minimum several weeks to months, eventually
becoming more than 100 meters thick and filling the bottom of the entire summit crater it
lies within.
Regardless, for people who live just `outside of the 10 kilometer exclusion zone such as
those in the city of Talabre, you should prepare for the possibility of eventual ashfall which
could be a dusting or more that would likely be associated with an explosive volcanic eruption
from Lascar, even if it occurs several months from now.
Thanks for watching!
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