Geology And Geophysics

Katmai an Active Alaskan Volcano



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Mt. Katmai, located in Alaska, is considered to be an active volcano. It is part of a system of active volcanoes that exhibit continued fumarole and hot spring activity. Mt. Katmai, while not dangerous to any major cities directly, could conceivably spew enough ash and particulate matter into the sky to block sunlight in the event of a major eruption.

Mount Katmai is located on a convergent margin at a subduction zone; still on the Alaskan mainland, but along the same line as the Aleutian Islands. The Pacific plate is pushing under the Canadian continental plate and creating a lot of magma. The volcano is clustered with several other volcanoes that are also considered active.

Mount Katmai is a stratovolcano, and has the eruptive characteristics typical to such volcanoes at convergent continental margins. It is believed that the predominant type of volcanic activity at Katmai is Plinian, with pyroclastic flows and lava domes also occurring. Other volcanoes in the vicinity show characteristics of a history of lava flows, fumaroles, and Strombolian activity.

"In the 10,000 years since the close of the last Ice Age, there have been at least seven explosive eruptions and many minor eruptions within the Katmai volcanic cluster (I 29.2:K 15/2004)." In June of 1912, Mt. Katmai was suspected of erupting. "Increasingly severe earthquakes in the days preceding the June 6th eruption led to the complete abandonment of the native villages in the Katmai region (I 29.2:K 15/2004)." Its peak was missing, and now only a caldera remained. Subsequent studies indicated that instead of erupting itself, Katmai's lava had been sucked away by the eruption of nearby Novarupta. This loss of magma caused Katmai to collapse into itself and form a large caldera (I 29.2:K 15/2). "Since 1912 there have been no more reports of eruptions from the Katmai-Novarupta system (Rosi et al, 2003)." Yet, still volcanic activity continued as "the vista in 1916 of the coalescing plumes of steam produced by these vents gave the valley its nameValley of Ten Thousand Smokes (I 29.2:K 15/2)."

Mount Katmai is still a geohazard. The volcano is still classified as active. "The high peaks of the park were formed by volcanic activity, and many are still active, occasionally emitting steam, smoke, ash, or lava. A major eruption or earthquake may occur at any time (I 29.2:K 15/2)."

In 1918 the area was designated Katmai National Park, and thus no new or rebuilt settlements exist close enough to the volcano to be in immediate danger. Nonetheless, should Katmai ever have a major eruption, it is possible that it could release enough smoke and particulate matter to block sunlight over an extensive area. "So black even if you put your hand two or three inches from your face outside you can't see it cause it was so dark (I 29.2:K 15/2004)." The ash cloud from the Novarupta eruption was of such quantity, "that all of the area of Kodiak was shrouded in darkness for more than 60 hours (Rosi et al, 2003)."

Other repercussions of a new eruption would be mostly environmental. Ash fallout could bury extensive areas around the volcanoes, leading to loss of life for both plants and animals. In the 1912 eruption, "within minutes, more than 40 square miles of an adjacent valley was buried by volcanic deposits that may be as much as 700 feet thick (I 29.2:K 15/2)." Concerning the effects of this incident in one of the local villages, Second Lieutenant W.K. Thompson, who was helping rescue villagers noted, "volcanic ashes had buried village to a depth of three feet on the level, closing all streams and shutting off the local water supply. Salmon were dead in the lake, and it was apparent that the fish would not return for some time (I 29.2:K 15/2004)."

Additionally, all of the debris thrown into the upper atmosphere in the 1912 event "quickly distributed over the whole world, so as to have a profound effect on the weather, being responsible for the notoriously cold, wet summer of that year (Griggs, 1917)."

However, such ash fallout can also have benefits. Kodiak, which is a hundred miles from the volcano "was buried nearly a foot deep in ash" and "redemption and revegetation seemed utterly hopeless (Griggs, 1917)." Two years later Griggs returned "to find the ash-laden hillsides covered with verdure (Griggs, 1917)."

Mount Katmai remains classed as an active volcano. The region is known for violent volcanic eruptions. Katmai is still a geohazard to this day, and will continue to be one for some time. Effects of a future eruption can only be guessed at, but an educated guess suggests that Katmai could, indeed, erupt violently again.



Bibliography

Griggs, Robert F.. 1917. The Valley of Ten Thousand Smokes. National Geographic Magazine. Volume XXXI, No.1. Washington.

Rosi, Mauro, Papale, Paolo, Lupi, Luca, and Stoppato, Marco. 2003. Volcanoes. Firefly Books Inc., Buffalo, NY.

I 29.2:K 15/2. Government Document. Katmai National Park Use Assessment. National Park Service.

I 29.2:K 15/2004. Government Document. Witness: Firsthand Accounts of the Largest Volcanic Eruption in the Twentieth Century. National Park Service.

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