Alaska's biggest volcanic eruptions

Alaska is known for many great things -- its wildlife, its culture, its scenery -- but that beauty and ecological diversity comes with a price. A year can't go by without someone being seriously injured or killed by one of Alaska's many wild animals. And among the many pristine peaks that dot the Alaska landscape lurk other, less innocuous mountains.

Many know that the 1964 "Good Friday" earthquake that devastated the area around Prince William Sound was the strongest earthquake ever recorded in the U.S., and the second-strongest recorded in the world. But more than 50 years prior, Alaska was also home to the world's largest volcanic eruption of the 20th century.

And while the 1912 eruption of Novarupta in the Katmai cluster of volcanoes on the Alaska Peninsula was the biggest of Alaska's many recorded volcanic eruptions, it's far from the only major eruption. Many Alaskans still remember numerous volcano eruptions, with accompanying ashfall and disruptions to travel, over the years.

Even now, two volcanoes continue to rumble away in the Aleutians. Mount Cleveland has awoken numerous times in the last year, and Mount Kanaga spat out a small ash cloud on Feb. 18, prompting a raised alert level and a warning for further potential eruptions.

Volcanic eruptions are just one more thing that Alaskans have learned to live with, like shoveling snow or feeling the ground shake as a temblor works itself out somewhere across the land. Below are five memorable eruptions from Alaska's past.

1912 eruption of Novarupta

Volcanic eruptions are measured on a scale of 1 to 7 on the Volcanic Explosivity Index (VEI), 7 being the most severe, apocalyptic, "super volcano" variety that generally only occur once every eon or so. In the 20th century, only two eruptions have been measured at a VEI 6, which scientists suggest can be described as an eruption of "colossal," "paroxysmal," even "cataclysmic" scope.

One of those VEI 6 eruptions came in 1991 at Mount Pinatubo in the Philippines, which killed almost 850 people. The resulting ash cloud dropped global temperatures by about half a degree Celsius. The other came in 1912, from the aptly-named Novarupta volcano on the Alaska Peninsula, about 290 miles southwest of Anchorage. It was the largest volcanic eruption of the 20th century, and one of the five largest eruptions in recorded history.

Remarkably, the June 6, 1912, eruption of Novarupta had a death toll of zero, largely attributable to a series of increasingly violent earthquakes in the days leading up to the eruption, prompting exoduses from nearby villages. That's according to "Witness: Firsthand Accounts of the Largest Volcanic Eruption in the Twentieth Century," by Jeanne M. Shaaf, an excellent resource on the eruption.

Novarupta is located in the Katmai cluster of volcanoes, a string of eight volcanoes about 15 miles long. When it erupted, Novarupta launched an ash cloud 100,000 feet -- that's about 20 miles -- into the air, which began falling on Kodiak Island within a few hours. Three days later, toward end of the eruption, ash was falling all in Seattle. The ash cloud would eventually drift over Africa.

Geologists originally attributed the eruption to nearby Mount Katmai, but in 1953, it was determined that the eruption had come from another, nearby vent that had essentially drained the magma from underneath the now-collapsed Mount Katmai. All told, the U.S. Geological Survey estimates that about 3 cubic miles of magma were expelled during the 1912 eruption -- about 30 times more than during the catastrophic eruption of Mount St. Helens in Washington state in 1980.

Fortunately, the eruption occurred when Alaska was sparsely populated. According to the USGS, "The heavy ash fall produced by a Novarupta-scale eruption occurring today in southern Alaska would bring the state's economy to a standstill and kill or injure hundreds. Clinics would be overwhelmed by people with eye, throat and lung damage."

For a volcano located in a remote area of the globe, ashfall can be the most devastating part, as it can end up choking the air hundreds of miles away. In "Witness," one 18-year-old recounted seeing the ashfall from the 1912 eruption for the first time after days of seclusion when the air was black with soot:

"…light is coming. Oh boy, just like snow. Can't see nothing. No kind of tree. All white to mountain. No kind of beach. No bluff. Nothing. All white, the big river. Filled up. No running, the water. Just like cement. That time get hard, boy. Lots of animals that time killed. Lots killed -- the bear…ducks and everything."

Novarupta hasn't erupted since, but the area surrounding the site of the eruption became known as "The Valley of 10,000 Smokes," where the ash-covered ground continued to sizzle for years.

1931 eruption of Aniakchak

Novarupta in 1912 led to much study and reflection on the impact and scale of the eruption, but the 1931 eruption of Aniakchak -- which, like Novarupta, is also located on the Alaska Peninsula -- almost went unnoticed.

Were it not for efforts of a missionary from a California university, Father Bernard Hubbard, the sizable eruption of Aniakchak, and its effects on the surrounding countryside, may have slipped into obscurity. Hubbard was initially drawn to Alaska to study glaciers in Southeast (earning him a nickname of "the Glacier Priest"), but the Katmai region and its landscape, still scarred by the Novarupta catastrophe, was where he made his mark on science, examining the volatile area around The Valley of 10,000 Smokes.

Most notable among these was the Aniakchak eruption, which began on May 1, 1931, according to the Alaska Volcano Observatory. Ash from the early stages of the Aniakchak eruption fell more than 350 miles away, and an "extremely violent eruption" occurred 10 days later, on May 11.

According to "Beyond the Moon Crater Myth: A New History of the Aniakchak Landscape" by Dr. Katherine Ringsmith, Hubbard and a team of explorers visited Aniakchak in 1930, mapping the already-existing crater and discovering the volcano to still be active. They returned in 1931, in the midst of the major eruption. According to one of Hubbard's traveling companions on that 1931 trip, Hubbard had predicted that the volcano would soon erupt, since it was a particularly active time for volcanoes on the Alaska Peninsula.

Ringsmith says that Hubbard's traveling companions were discouraged upon learning that the volcano was erupting, but Hubbard's enthusiasm only grew, as it offered an opportunity for a comparative expedition to the 1930 trip. Aniakchak hadn't erupted in more than two centuries, so the changes were remarkable. An eager Hubbard even flew over the crater while the volcano was still active, nearly being sucked into the superheated caldera by a downdraft.

Scientists today use Father Hubbard's observations from Aniakchak in 1930 to study the return of vegetation and wildlife to the area around the volcano. Aniakchak is now a National Monument, with the volcano's 6-mile-wide and 2,000-feet-deep crater as the centerpiece. The Park Service says it is "one of the least visited parks" in the nation.

Want to see it? Check out this video by outdoor enthusiast Luc Mehl, who journeyed to the crater with a group of fellow adventurers in summer 2011. Read much more about Aniakchak in "Beyond the Moon Crater Myth."

1944 eruption of Mount Cleveland

Mount Cleveland, one of the most active volcanoes in Alaska, has seen its fair share of eruptions. But perhaps the 1944 eruption was most notable. Despite other, larger eruptions in Alaska's recent history, an eruption in 1944 was responsible for the only death directly attributable to volcanic activity in the state, according to the Alaska Volcano Observatory.

The 5,676-foot Mount Cleveland, located in the Aleutian Islands, is about 45 miles from the small community of Nikolski. Despite the volcano not having any real-time monitoring equipment, it has seen at least 24 confirmed eruptions in the last 200 years, with other questionable events that could push the number to 32, dating as far back as 1774. Even now, a lava dome is slowly growing in the crater of Mount Cleveland, similar to activity that occurred before a minor ash emission last December.

But Cleveland's most notable eruption was surely the one in 1944, if only for its lone human casualty. In midst of World War II, the Aleutians became a hub for U.S. military forces, with more than 40,000 troops stationed in the region after the Japanese occupied the islands of Attu and Kiska. In 1944, a small group of soldiers from the 11th Army Air Force were stationed on Chuginadak Island, where Mount Cleveland is located.

All things considered, it wasn't necessarily unwise to have troops stationed on the island in 1944. The volcano had last erupted in 1938, and it took another seven years for the mountain to erupt again in 1951.

But as the volcano came to life on June 10, 1944, a soldier identified as Sgt. Purchase went for a walk around the island, something he'd done before. Other soldiers, feeling minor temblors and seeing the mountain begin to smoke, went after him along the beach. They spotted him from a distance, but eventually reached a point where his tracks stopped and a mudslide was coming off the mountain.

The men saw a flow of lava coming down the mountain behind them, threatening to cut off their return path. The men then hunkered down for the rest of the three-day eruption, waiting for the volcano to finish its unrest.

The AVO reports that one lieutenant accounted for the volcano's activity on the morning of June 12th:

"At 7 a.m. the volcano was plainly visible. The sky was clear and we saw that the rim of the crater was slightly inclined to the south of the apex. Violent eruptions were taking place, although no lava was flowing at this time. A never-ending fountain of boulders about 20 to 40 feet in diameter were being thrown from 1,000 to 2,000 feet straight into the sky."

Following the 1944 eruption, the outpost was abandoned for the duration of World War II.

1989-1990 Eruption of Mount Redoubt

The 1989 eruption of Mount Redoubt wasn't exactly among the largest in Alaska during the 20th century -- the peak activity merited a Volcanic Explosivity Index rating of 3 on a scale of 1-7 -- but it was among the most disruptive and expensive. It's also fresh in many Alaskans' memories, as it occurred much closer to the state's largest city of Anchorage than those larger eruptions taking place in the Aleutians.

The eruption lasted from December 1989 until April 1990, with 23 major explosive events in that time. The multiple explosions rained ash over a good portion of the Cook Inlet region and Southcentral Alaska, and in its early stages seriously hindered air travel. A National Weather Service report estimates that the eruption cost about $160 million, making it the second costliest volcanic eruption in U.S. history, with only the massive Mount St. Helens eruption of 1980 costing more.

The eruption began on Dec. 14, 1989, when Mount Redoubt -- located about 100 miles southwest of Anchorage, across Cook Inlet -- spat an ash cloud into the sky following a day of intensifying seismic activity. The timing was particularly bad, with the busy holiday travel season just getting under way.

KLM flight 867, a Boeing 747 headed for Anchorage International Airport, flew through the ash cloud at an altitude of about 25,000 feet, which resulted in all four of the aircraft's engines dying. After plunging more than two miles to about 13,000 feet, the pilots were able to restart the engines and land safely at the airport. The cost of damages to the plane alone? About $80 million.

The AVO reports that "about 20 significant tephra deposits" resulted from the lengthy eruption, interrupting air travel numerous times and scattering ash on the Kenai Peninsula that led to more than 1,000 days in lost labor and three days of school closures.

Redoubt wasn't finished, either; in 2009, Redoubt erupted again, prompting flight cancellations and a slight ashfall in Anchorage.

1976 and 1986 eruptions of Mount Augustine

In one decade, Mount Augustine, located on its namesake Augustine Island about 170 miles southwest of Anchorage, erupted violently twice. Augustine Island is made up almost entirely of volcanic deposits from the 4,134-foot peak that sits atop it. In 1976 and 1986, eruptions that both reached a magnitude of VEI 4 had a similar effect on air traffic as the 1989 Mount Redoubt eruption, and both eruptions coated Southcentral Alaska with ash.

In 1976, Augustine launched an ash cloud more than 8 miles into the sky, causing ashfall across the Kenai Peninsula. Part of the ash cloud was visible as far away as Arizona within a couple of days of eruption. The Alaska Volcano Observatory reports that this eruption was accompanied by a particularly violent pyroclastic flow, a superheated mix of hot gas and debris discharged by the volcano, that spread across the small island.

A tiny research station on the island -- thankfully unmanned at the time of eruption -- showed evidence of the violence of the eruption. T. Neil Davis, writing for the University of Alaska Fairbanks Geophysical Institute, described the damage in particularly alarming language:

The 1986 eruption was similar, with ashfall again scattering across the Kenai Peninsula and falling in Anchorage during a long eruption that lasted nearly six months, from March 27 to Sept. 10. That eruption led experts to warn that Augustine may have been approaching a breaking point that could lead to an eruption similar to the 1980 eruption of Mount St. Helens in Washington.

In that eruption, the north face of Mount St. Helens sloughed off as result of an earthquake, creating a fast-moving landslide that exposed the magma that had been resting inside the mountain. When the magma was released from the high-pressure confines of the mountain and exposed to the lower pressure of the surrounding environment, it burst out in a massively destructive pyroclastic flow that flew off the mountain at nearly 700 mph, snapping trees in half and burying the surrounding countryside in debris. The lateral blast traveled 17 miles northwest of the volcano.

An April article in the Anchorage Daily News about a week after the most explosive activity from the 1986 eruption warned that Augustine may be in for a similar fate. The other eruptions had left a 700-foot-long crack on the south face of the mountain, and volcanologists determined that water and magma were mixing inside the volcano to create a high pressure situation that could be triggered by further seismic activity. The amount of earth that could be moved and Augustine's island location could trigger tsunamis were such a landslide to occur, and Kenai Peninsula authorities warned residents of such a possibility as the 1986 eruption continued.

Fortunately, such a scenario never materialized, and in the decades since, Augustine has been relatively quiet. A VEI 3 eruption occurred in December 2005 and extended to March 2006, but resulted in only minor flight cancellations and no major health threats.