When it comes to the region of the planet with the most volcanoes in a small area, nothing
compares to the numerous volcanoes within the scenic Katmai National Park and Preserve
within Alaska as it contains 13 active volcanoes.
While several of these volcanoes have thick lava flows that are quite prominent such as
Novarupta and Trident, others do not as their lava flows remained buried by thick glaciers.
One such remarkable volcano contains 10 separate and prominent glaciers, and its summit stands
at 7,090 feet or 2,161 meters above sea level.
Known as Snowy Mountain, more than 90% of this scenic volcano is covered by glaciers.
Snowy Mountain last produced an eruption in 1760, forming a large lava dome.
Although it has not erupted since then, Snowy Mountain is definitely still active.
In 2000, a new hydrothermal feature known as the Snowy Hole appeared, which began to
release volcanic gasses from a fumarole at a low intensity.
For context, Snowy Mountain is located on the Aleutian Peninsula where it is 93 miles
west northwest of the city of Kodiak.
Along with the other adjacent volcanoes, Snowy Mountain exists due to the offshore collision
of two large tectonic plates.
There, the Pacific Plate is subducting underneath the North American Plate.
The melted material from this collision then migrates upwards, until it erupts onto the
surface, forming a chain of volcanoes.
Snowy Mountain consists of three separate snow covered peaks along a glaciated east-northeast
trend.
The western of the two peaks represent eroded segments of highly viscous lava flows, which
most likely originated from separate small volcanic cones that have been largely removed
by glacial erosion.
In contrast, the easternmost cone represents a large lava dome which grew out of a collapse
scar.
Although the exact geologic history of these vents is unclear, each peak trending to the
east seems to represent progressively younger activity.
Snowy Mountain began forming 200,000 years ago, when a volume of magma intruded into
a preexisting high ridge.
As it interacted with glacial cover, it produced a series of explosions, carving out a several
hundred foot wide crater in the ground.
Now coated with a layer of ash, viscous andesite lava poured into the crater.
This lava eventually overtopped the crater, and slowly advanced downslope to the west,
travelling about 2 miles.
Over the next several thousand years more eruptions occurred, creating a stratocone
out of overlapping layers of lava and ash.
A second volcanic cone later began erupting a mile and a half to the northeast, building
a secondary peak.
Although these two features may have erupted intermittently for as many as 175,000 years,
the total eruptive products of these cones is surprisingly small.
Cone 3 only has a volume of 5 cubic kilometers while cone 2 has a volume of 8 cubic kilometers.
For context, the nearby Mount Martin volcano has a volume of a little over 5 cubic kilometers,
but all of this material was extruded in the last 6,000 years.
After a long period of activity, the easternmost cone began to experience significant levels
of hydrothermal alteration, causing the surface rock to turn shades of red and yellow.
Then, sometime between 1500 and 600 years ago, a large volume of dacite composition
magma intruded underneath this cone in what is termed a cryptodome.
Uplift of the mountain soon reached a critical point, causing 450 million cubic meters of
rock to collapse to the north in a massive landslide.
In total, this landslide covered 8.7 square miles with a thick layer of rock, and material
travelled up to 15 miles from its source.
In 1760, a large lava dome extruded onto the eastern half of the newly formed collapse
scar, refilling much of the crater.
Although Snowy Mountain has not erupted since, it is likely to produce more small collapses
in the future.
As a result of this and other hazards, the US Geological Survey designated Snowy Mountain
as a high threat volcano.
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