Millions of people live in the shadow of deadly volcanoes around the world, and recently two volcanoes near heavily populated areas have spewed massive clouds of ash, triggered small earthquakes, and put authorities on the alert.
In the Philippines, the Taal Volcano near Manila, emitted a huge plume of ash Jan. 13 and authorities in the area have declared a state of calamity and raised the alert level to 4 out of 5, with 5 being an eruption in progress. According to reports, Philippine authorities have urged a "total evacuation" of nearly a million people near the capital Manila and are warning of an imminent eruption. Taal is only about 40 miles south of Manila, one of the most densely populated cities in the world. The Manila metro area has a population between 12 million and 24 million people.
Meanwhile, one of the most active volcanoes in Mexico and about 45 miles from Mexico City, Popocatepetl, pictured above in an undated photo, released a huge cloud of ash 19,000 feet into the sky Jan. 9, according to the Volcanic Ash Advisory Center in Washington. The disaster authority in Mexico that monitors the volcano says that Popocatepetl has been releasing vapor and volcanic gases since last week, and surveillance cameras recorded an explosion Jan. 10 that ejected glowing red fragments into the sky. People are being warned to stay away from the volcano, because of the risk of ballistic fragments and possible mudslides.
Popocatepetl, pictured above, is one of the most active volcanoes in Mexico and has had more than 15 major eruptions in 500 years. The greater Mexico City area has a population of more than 20 million people.
Despite the risk, millions of people around the world live within reach of the deadly forces of volcanoes. While lava is usually too slow to run over people, active volcanoes are associated with violent earthquakes, avalanches, mudslides, tsunamis, huge clouds of suffocating ash and harmful gases.
In the 1990s, the International Association of Volcanology and Chemistry of the Earth's Interior created a list of 16 of the deadliest volcanoes, called Decade Volcanoes, worthy of special study because of their great potential for destruction. While Popocatepetl is not one of them, Taal is.
Eruptions of these volcanoes may threaten tens or hundreds of thousands of people, and many eruptions can produce a dense, destructive mass of hot ash, lava fragments, and gases ejected explosively, flowing downslope at great speed toward the cities and towns below.
These are the world's deadliest volcanoes.
Taal is actually a volcano within a lake formed by the 18-mile wide caldera of a larger volcano. The island in Taal Lake is known aptly as Volcano Island. It also contains a crater lake. It's essentially a lake inside a volcano, in a lake inside a larger volcano.
NASA describes Taal as a formation of multiple stratovolcanoes, conical hills, and craters of all shapes and sizes that have grown together to form the 3-mile wide Volcano Island.
All volcanoes of the Philippines are part of the Pacific Ring of Fire. There have been more than 33 recorded eruptions at Taal since 1572.
Mexico's Colima volcano has erupted more than 40 times since 1576. It is one of the most active volcanoes in Mexico and in North America. One of the largest eruptions was on January 1913, and it was very active in 2017.
Colima is located in the state of Jalisco, about 300 miles from Mexico City and 78 miles from Guadalajara. About 300,000 people live within just 25 miles of Colima, making it the most dangerous volcano in Mexico.
Italy's Mount Etna, on the island of Sicily, has had historically recorded eruptions for the past 3,500 years.
Looming over the city of Catania, Etna is one of the most active volcanoes in the world and is in an almost constant state of activity. It is currently in the midst of a series of eruptions that began in 2001, according to geology.com.
Etna is prone to violent explosions and voluminous lava flows. About a quarter of Sicily's population lives on its slopes.
Etna it is the main source of income for Sicily, primarily agriculture, (thanks to the rich volcanic soil) and tourism. Above, hikers on an excursion up the mountain in 2015.
In the image above taken from the International Space Station, winds carry the eruption plume and smoke from fires triggered by the lava as it flows down the 11,000-foot Mt. Etna in 2002.
Mauna Loa (U.S)
Hawaii's Mauna Loa is the largest active volcano on Earth. It has erupted 33 times since its first well-documented historical eruption in 1843. Voluminous flows of lava have reached the ocean eight times since 1868. It last erupted in 1984, when a lava flow came within 4.5 miles of Hilo, the largest population center on the island. Above, the lava flow from Mauna Loa during its 1984 eruption.
The enormous Mauna Loa makes up half of the entire island of Hawaii. It is one of five volcanoes on the island, and part of Hawaii Volcanoes National Park.
This is a pair of volcanoes, located on the Kamchatka Peninsula in Russia's far east, that have erupted at least 16 times since 1737. A large explosive eruption occurred at Avachinsky in 1945, according to Oregon State University.
The most recent eruption was in 1991 and produced lava flows, a dome, and mudflows. The image above shows the Russian city Petropavlovsk-Kamchatsky, with a population of about 178,000, at the foot of the volcanoes.
The volcanoes are a draw for tourists. Above, tourists hike to the top of Avachinsky in 2014, in the background is the Koryaksky Volcano.
Just west of the city of San Juan de Pasto in western Colombia, Galeras is one of Colombia's most frequently active volcanoes, and has been active for more than 1 million years, according to Oregon State University.
In 1993, volcanologist Stanley Williams was standing on top of Galeras when it erupted, killing six of his colleagues instantly. As Williams tried to escape the blast, he was pelted with white-hot projectiles traveling faster than bullets. Within seconds he was cut down, his skull fractured, his right leg almost severed, his backpack on fire. Williams lay helpless and near death on Galeras' flank until two women — friends and fellow volcanologists — mounted a rescue effort to carry him safely off the mountain. Williams recounts the experience in his book, "Surviving Galeras."
Situated between Central Java and Yogyakarta, Indonesia, Mount Merapi is the most active volcano in Indonesia and has erupted regularly since 1548.
In 2010, eruptions at Mount Merapi produced ash plumes, gases, debris flows and sulfur dioxide, a colorless gas that can harm human health and cool Earth's climate.
Above, a house lies destroyed by ash on the upper slopes Merapi after an eruption June 25, 2006 in Central Java.
The 9,560-foot Merapi, also known as the Mountain of Fire, is popular among climbers. From the nearest village, it's about three hours to the top. Above, climbers reach the smoking caldera at sunrise.
Nyiragongo (Democratic Republic of the Congo)
According to Oregon State University, Nyiragongo volcano, located in the Democratic Republic of Congo, has been a rather active volcano, but because of political unrest in the area, it is not as well studied by scientists.
Twice in recent history, Nyiragongo has had two devastating volcanic eruptions. The lava from this volcano flows faster than the lava in Hawaii, where people can easily escape it— Nyiragongo's flows travel as fast as 60 mph.
In January 1977, the crater wall holding the lava lake, shown above, ruptured. Within 30 minutes, the entire lava lake had drained, sending an estimated 3 to 5 million cubic meters of lava to the north, west, and south of Nyiragongo. These lava flows reached up to 62 mph, wiping out several of the surrounding villages and burning almost 300 people alive, according to OSU.
Above, guards of Virunga National Park sit in the glow of Nyiragongo's crater.
Mount Rainier, the highest peak in the Cascade Range at 14,410 feet, is the most threatening volcano in the Cascades, according to the USGS. Besides its elevation and its proximity to Seattle and the Puget Sound region, Ranier's threat comes from its potential for producing volcanic ash, lava flows and avalanches of intensely hot rock and volcanic gases that swiftly melt snow and ice and produce torrents of meltwater that pick up loose rock and become rapidly flowing slurries of mud and boulders.
While the last recorded eruption of Rainier occurred in 1840, the volcano is continuously monitored by the USGS. The population of the Puget Sound region is nearly 4 million people.
Lava flows from an eruption of Japan's Sakurajima in 1914 actually filled the narrow strait between the island and the mainland, connecting the volcano's island to the Osumi Peninsula. Above, Kagoshima City near the mountain.
The volcanic activity at Sakurajima continues, erupting over 800 times in 2010, and dropping volcanic ash on the surrounding areas.
Sakurajima's most recent eruption began on May 2, 2017.
Santa Maria (Guatemala)
Until 1902, Santa María volcano was inactive for at least 500 to several thousand years, according to Michigan Tech University. In 1902 Santa Maria erupted violently following a series of earthquakes. Despite the warning signs, the eruption killed at least 5,000 people and tore a gaping hole in the south flank of the cone, darkening the skies over Guatemala for days. Pumice fell over an area of about 105,000 square miles and ash from Santa Maria was detected as far away as San Francisco, Calif.
The catastrophic eruption and partial collapse of Santa María created a dome complex that grew inside the collapse scar, which looms over this sugarcane field, above, in Retalhuleu, Guatemala.
Pristine villages of white houses sit on the brink of the crater of this volcano — the blue water seen here fills the crater itself. Santorini and two other islands are what remain after a huge eruption over 3,600 years ago.
Water from the Aegean Sea rushed in to fill the void, forming the central, 7.5-mile lagoon. The eruption in 1620 B.C. destroyed or submerged much of the previous island of Santorini; this event may have been the inspiration for the legend of the "lost continent" of Atlantis.
This image from NASA shows the three pieces that remain of the original island of Santorini.
Archaeological excavations at the town of Akrotiri reveal the remains of a Minoan-age town with streets, three-story houses, and frescoes well preserved under ash layers, much like those preserved at Pompeii.
The 12,198-foot Mount Teide is a volcano on Tenerife in Spain's Canary Islands. In recent centuries, the most devastating eruption was in 1706, when the town of Garachico, above, was completely destroyed. Today, the volcano and its surroundings comprise Teide National Park.
Above, the Teide astronomical observatory with the volcano in the background.
Ulawun (Papua New Guinea)
In recent years there has been almost constant activity at Ulawun, with frequent small explosions. According to Volcano Live, the first recorded eruption of Ulawun was in 1700. An eruption in 1980 ejected ash as high as 60,000 feet and produced lava flows which swept all flanks of the volcano and devastated an area of over seven square miles. The most serious volcanic hazard at Ulawun volcano is catastrophic structural collapse, producing an eruption which could devastate hundreds of square kilometers.
Unzen is a large complex volcano made of several adjacent and overlapping lava domes, according to Oregon State University. In 1792, collapse of the a lava dome created an avalanche and tsunami that killed an estimated 14,524 people. The hot springs of Unzen in Shimabara, seen here, are a popular attraction.
Unzen was most recently active from 1990 to 1995, and a large eruption in 1991 generated a debris flow that killed 43 people, including three volcanologists. The volcano covers much of the Shimabara Peninsula and is about a 30-minute drive from the city of Nagasaki, above.
Just about 5 miles east of Naples, Mount Vesuvius is famous for its eruption in AD 79 that destroyed the Roman cities of Pompeii and Herculaneum, killing more than 1,000 people.
Vesuvius has erupted many times since, and is the only volcano on the European mainland to have erupted within the last hundred years.
Today, Pompeii, once a thriving and sophisticated city of over 10,000, is a vast archaeological site. When Vesuvius erupted, residents were killed by falling debris and asphyxiated by ash that buried the city up to 23 feet deep. Bodies of those trying to escape were preserved in the ash for centuries.
The preserved site features excavated ruins of streets and houses that offers a unique insight into Roman life over 2,000 years ago.
Today, Vesuvius is regarded as one of the most dangerous volcanoes in the world because of the population of 3 million people living nearby, and its tendency towards violent, explosive eruptions.