Despite how much has been learned about the Earth and its more than 1,000 active volcanoes,
several things in the field of volcanology remain a mystery.
For instance, in the past 10,000 years, there were several supermassive volcanic eruptions
which caused worldwide famines and volcanic winters, each being more than 100 times the
size of the 1980 eruption of Mount Saint Helens.
The most recent example of such was the 1815 eruption of Mount Tambora in Indonesia which
caused the so-called "year without a summer".
However, the origin of several other similarly sized recent eruptions remains a mystery.
We do not truly know the source of large volcanic eruptions in 535, 1465, and 1808.
Heading towards the western third of Canada, there is another such mystery.
In British Columbia, two ash layers were discovered at several locations, and dated to 10,600
years ago.
These layers of ash were the result of two closely spaced large explosive eruptions from
the same volcano.
Yet, the composition of these ash layers does not match any known Canadian volcano particularly
well.
You would think that two very large recent eruptions would leave behind obvious signs
on their volcano of origin...but nothing obvious stands out nearby.
So, which volcano created these two mysterious eruptions, which would have been similar in
size to the 1990 eruption of Mount Redoubt in Alaska?
The aforementioned sets of ash are referred to as the "Finlay tephras".
They are found at several locations in far northern British Columbia, where they are
spread across an area of at least 17,000 square kilometers.
This section of Canada contains the most numerous and most active volcanoes in the country.
Here, the crust is slowly spreading apart to the east and west, allowing for magma to
travel up through the crust and erupt onto the surface.
This has created 6 separate volcanoes which are close enough to be the source of this
ash.
With this being said, only half of these volcanoes have been extensively studied and had their
young eruptions dated.
Thus, potential young volcanic eruption sites have yet to be identified.
With this being said, two of these volcanoes can be immediately disregarded.
Despite being the most active volcanic field in the country, the Inskut Unuk River Cones
does not produce highly explosive non cinder cone forming eruptions.
Thus, it cannot be the volcano of origin.
The second volcano known as Hoodoo Mountain seems at first like a close match, but cannot
be the source of the ash as it was located beneath a thick glacier at the time of the
eruption.
Additionally, for the ash to be dispersed over a wide area, it generally follows an
eastward path.
Yet, the closest core drilled to Hoodoo Mountain did not have either of the two Finlay tephras
present.
To the north, the two closely spaced volcanoes Mount Edziza and the Spectrum range seem like
good candidates as they are very closeby.
However, despite each producing several young eruptions, these two volcanoes erupted the
wrong type of lava.
The finlay tephras are composed of phonolite ash and these primarily erupted basalt.
The only two remaining candidates have next to zero information on them, mainly due to
their extreme remoteness and lack of nearby settlements.
Both of these volcanoes are considered to be active as they have young looking volcanic
products on them.
However, the Heart Peaks volcano also does not erupt phonolite.
Thus, by process of elimination, it seems reasonable that the Finlay Tephras originated
from the largest still active volcano in Canada, Level Mountain.
The exact site of origin for these two eruptions on this volcano is unknown, but will likely
be uncovered through future more extensive studies.
Both of these ancient eruptions were highly explosive, rating on the volcanic explosivity
index as a 3 or 4.
Thus, Level Mountain is a much more active volcano than we initially suspected.
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