The United States contains 162 active volcanoes. Of these, 85 are located in Alaska. Although many
of the volcanoes close to cities such as Anchorage are well known, other more remote volcanoes are
not. This video will discuss the northernmost volcano in all of Alaska, known as Imuruk Lake.
It produced a massive lava flow about 1600 years ago, and will certainly erupt again.
The Imuruk Lake volcano can be found in far western Alaska on the Seward peninsula.
The closest town to this volcano, called Deering, is located 45 miles to the north.
This volcanic complex covers an area of 900 square miles, and could best be described
as a volcanic field. It doesn't contain any central peaks, but rather an assortment of
75 basaltic vents which formed both cinder cones and low prominence shield volcanoes.
The Imuruk Lake volcanic complex began forming 6.1 million years ago,
when a volume of magma reached the surface on the Seward Peninsula. We aren't yet sure exactly why
this volcanic field exists here, but one possible explanation is that the location represented
a natural weak or thin point in the crust. When this magma reached the surface, it erupted
in a several hundred foot high fountain of lava. As lava continued to spew out, it intermittently
ejected small volumes of ash, which fell close to the erupting vent. This in turn built a small
and cylindrical vent known as a cinder cone. Lava flows from these cinder cones frequently
traveled more than a dozen miles from an erupting vent, although during periods of thick ice cover,
the lava did not travel as far. Although some vents only erupted once and never erupted again,
others continued to erupt over much longer timespans. These vents likely erupted
intermittently for tens of thousands of years, and over time built a gentle sloped shield volcano.
By 2.2 million years ago, more than four dozen of these cinder cones and shield volcanoes had
formed. These lavas covered a vast area of several hundred square miles with black volcanic rock,
which interestingly contained a high amount of a gemstone known as sphene.
For the next 1.3 million years, there are no records of any eruptions, indicating a period
of dormancy. Although it is quite possible that small eruptions did occur, any evidence
of such was likely lost in the geologic record. Volcanic activity then resumed 900,000 years ago,
northwest of Kuzitrin Lake. Over a span of several thousand years,
numerous effusive eruptions built two overlapping 300 foot tall and 2 mile wide shield volcanoes.
After these became extinct, the lava beneath them traveled elsewhere in the volcanic field.
This caused the overlying rock to collapse downwards, thus forming two adjacent calderas.
After a series of additional eruptions built a half dozen volcanic cones, this field became
dormant once again. then, 18,000 years ago, a new vent called Camille suddenly erupted.
Lava from this volcano flowed outwards in every direction, but generally was funneled
in a westward direction, since that direction gently sloped downhill. By the time the eruption
had ended, an area of 30 square miles was covered with a 30 foot thick layer of lava.
Then, in 365 AD, the most recent and largest eruption from this volcano occurred. Over the span
of what likely lasted a year, a small cinder cone called the Lost Jim Cone erupted a vast volume of
lava which covered 88 square miles or 228 square kilometers. Lava from this eruption in some places
traveled more than 25 miles before it cooled. Since then, no additional eruptions have occurred.
Due to the Imuruk volcano's remoteness and its nonexplosive history, if it was to erupt anytime
soon, it wouldn't pose much of a threat to anyone. As a result, when the US geological
survey rated this volcano, it was ranked dead last in terms of overall threat out of all of
the country's volcanoes. Regardless, this very low threat volcano will eventually erupt again,
with the odds of a new eruption being about 1 in 18,000 each year.
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