10 Volcanoes That Pose Significant Threats

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We live on an active planet. Every year, some 50 to 70 volcanic eruptions occur somewhere in the world, some featuring slow pyroclastic flows, others causing violent explosions. As the recent eruption of the Popocatepetl volcano near Mexico City reminds us, many of these hotbeds of activity sit dangerously close to population centers. Following are 10 volcanoes that the International Association of Volcanology and Chemistry of the Earth’s Interior is closely monitoring due to their potential for eruption and their proximity to large populations. The list is in no particular order, as the IAVCEI did not rank the specific threats posed by these volcanoes.


10. Rainier (United States)

An eruption of Mount Ranier would pose a significant threat to the Puget Sound region.

Mount Rainier is a picturesque part of the Seattle skyline; © Docbombay/Dreamstime.com

Eruption of this iconic volcano in the Northwestern U.S. could have huge implications for Seattle, Tacoma and other cities in the Puget Sound region. Mount Rainer’s last major eruption occurred in 1894-95, and the region is much more heavily populated today. The biggest danger from a stratovolcano such as Mount Rainier is the creation of lahars, or fast-moving walls of mud and debris. These lahars, up to 100 feet thick and traveling up to 50 mph, could reach Puget Sound, some 40 miles away, wiping out everything in their path. According to the United States Geological Survey, scientists have determined that at least one such lahar in Mount Rainier’s past occurred without warning, while the volcano was quiet. In such a rare instance, a warning could only be issued after the lahar had started its destruction. About 80,000 people live in Rainier’s lahar-hazard zones. Based on past eruptions, the USGS puts the odds of such threatening events at only about 1-in-10 in an average human lifespan.


9. Vesuvius (Italy)

Some of the area near Mount Vesuvius is more densely populated than Hong Kong.

Mount Vesuvius viewed from the ancient remains of Pompei; CCA-SA 3.0 Morn the Gorn

One of the most infamous natural disasters in history occurred one morning in August 79 A.D. The eruption of Mount Vesuvius annihilated the Roman cities of Pompeii and Herculaneum with ash flows, noxious gas, and cinder bombs composed of explosive flying rocks. Today, the large metropolis of Naples sits within sight of the still-active volcano, which last had a large-scale eruption in March 1944. More than 600,000 residents live in the danger zone of this volcano. The dense population concentration so concerns authorities that a few years ago they began a relocation program for residents, offering pay of $30,000 (U.S. dollars) per family to move. They found few takers.


8. Avachinsky-Koryaksky (Russia)

Twin volcanoes of Avachinsky and Koryaksky pose a threat to the Russian seaport of Petropavlovsk-Kamchatsky.

Mount Koryasky towers over Avacha Bay;  Vfp15

Located on the Kamchatka Peninsula in extreme eastern Russia, the city of Petropavlovsk-Kamchatsky is literally surrounded by active volcanoes. The Koryaksky and neighboring Avachinsky volcanoes both have a history of eruptive activity. The last major eruption of Koryaksky occurred in December 2008, sending an ash plume 20,000 feet into the atmosphere. A 2010 census recorded 179,526 people living in the area, which is used as a Russian naval port.


7.  Nyiragongo (Democratic Republic of Congo)

Mount Nyiragongo features one of the world's largest lava lakes.

Mount Nyiragongo’s spectacular lava lake; Cai Tjeenk Willink

Located in the Virunga Mountains in the heart of Africa, Mount Nyiragongo contains one of the largest lava lakes ever recorded, and together with nearby Mount Nyamuragira accounts for 40 percent of all the historic eruptions on the African continent. In 2002, a major eruption occurred, killing 147 people, mostly due to asphyxiation caused by a large release of carbon dioxide. The large city of Goma, with a population of over 377,000, sits in the danger zone of this volcano.


6. Santa Maria (Guatemala)

Santa Maria's 1902 eruption is one of the most violent of the past several hundred years.

Santa Maria volcano, from nearby town of Quetzaltenango.

In 1902, one of the most violent volcanic eruptions of the past several hundred years occurred when this Central American stratovolcano exploded. Santa Maria ejected a pumice cloud over a 100,000-square-mile area, and the southwestern side of the mountain was destroyed, killing more than 5,000 people. To put the power of that eruption in perspective, volcanologists use a Volcanic Explosivity Index ranging from 0-8 to rate eruptions. VEI Ratings of 2-4 are considered “Explosive,” while 5 is rated “Cataclysmic.” The 1902 Santa Maria eruption rated a 6, considered “Paroxysmal.” That was the same rating assigned the infamous explosion of Krakatoa in 1883. Today, the metropolitan area of Quetzaltenango, with some half-million residents, sits within the shadow of this active volcano.


5. Mauna Loa (United States)

Mauna Loa is the largest volcano on Earth.

A lava flow from Mauna Loa during its 1984 eruption; USGS

The largest volcano on Earth, Mauna Loa is a massive shield volcano that comprises over half of the landmass of the large island of Hawaii. The first documented eruption was in 1843, and the most recent occurred in 1984. Mauna Loa is one of the most active volcanoes in the world, with 33 eruptions in that span. Hilo, the largest city on the island with a population of 43,263, sits on a lava flow formed in the 19th century, and the Mauna Loa Solar Observatory also sits on its flanks.


4. Galeras (Columbia)

A 1993 eruption of Mount Galeras killed nine people.

Mount Galeras towers over the city of Pasto; José Camilo Martínez

Part of the Pacific Ring of Fire, Mount Galeras most recently erupted twice in 2010, forcing the evacuation of some 8,000 residents. The volcano is the most active in Columbia, and claimed the lives of several tourists and six scientists who were sampling the gases of the caldera when it erupted in 1993. Almost 400,000 individuals live about six miles away from this volcano in the city of Pasto, which was blanketed in ash during a 2005 eruption.


3. Sakurajima (Japan)

Sakurajima in Japan erupted as recently as 2009.

Sakurajima poses a threat to the city of Kagoshima; Kimon Berlin

Located on the southern tip of the island of Kyushu in Japan, the summit of this stratovolcano is split into three distinct peaks, the southernmost of which is currently active. The 1914 eruption was the most powerful recorded in Japan in the 20th century, and actually created a peninsula connecting Sakurajima Island with the mainland. The lava flows generated by Sakurajima persisted for months, filling in parts of Kagoshima Bay and raising annual tide levels. Today, the large Japanese port city of Kagoshima with a population of more than 600,000 sits across the bay, and recent eruptions in March 2009 serve as a reminder that this large volcano is still extremely active.


2. Colima (Mexico)

Some 300,000 people live within 25 miles of the Colima volcano in Mexico.
One of the most active volcanoes in North America, Colima has erupted over 40 times since the first recorded event in 1576. A population of more than 300,000 lives within a 25-mile radius of this volcano, which is located about 75 miles south of Guadalajara. In 2005, the volcano erupted twice, sending an ash cloud 10,000 feet into the air and hurling explosive lava bombs over two miles away. The activities of Colima have forced evacuations on several occasions.


1. Etna (Italy)

Mount Etna is one of Italy's most famous natural features.

Mount Etna’s 2002 eruption photographed from the International Space Station; NASA

Located on the island of Sicily, Mount Etna is one of the most well-documented and active volcanoes in the world. Mount Etna has been the site of near-continuous lava flows and occasional eruptive explosions, most recently from 1991 to 1993, with some of the latest eruptions occurring in early 2012. Mount Etna is the result of the convergence of the Eurasian and African plate boundaries, and is the highest volcano in Europe at 10,922 feet in elevation, more than twice the height of Mount Vesuvius. More than 5 million people reside on Sicily, and the rich volcanic soils of the island support a thriving viniculture.



Image credit: United States Geological Survey

The International Association of Volcanology and Chemistry of the Earth’s Interior is closely monitoring six other so-called “Decade Volcanoes,” that can be found on this USGS website.

Written by

David Dickinson is a backyard astronomer, science educator and retired military veteran. He lives in Hudson, Fla., with his wife, Myscha, and their dog, Maggie. He blogs about astronomy, science and science fiction at www.astroguyz.com.