Forty-three miles southeast of Mexico City, 17,802-foot Popocatépetl (the name means smoking mountain) lay dormant the first half of the 20th century but has been increasing in activity since the early 1990s, when it exploded in a plume of gas and ash that carried more than 15 miles.
Now “Popo” is rumbling again. In April, the volcano put on a show of glowing rock and spewing vapor. At some points the volcano even emitted a low-pitch roar, blasting ash upward and hurling superheated rock fragments into the air—a result of built-up pressure from magma beneath its slopes.
Popocatépetl is a stratovolcano, a type that is conical in shape and produces thick, slow-moving lava, which scientists say is unlikely to do much physical damage to the area. Still, if Popocatépetl continues to gush ash clouds and steam plumes, it could wreck havoc on air travel to and from Mexico City and dislocate tens of thousands of nearby residents—particularly in the area’s farming villages.
Rising off the island of Sulawesi, twin-peaked Lokon-Empung is one of Indonesia’s most active volcanoes. The 5184-foot Lokon peak is the older and flatter of the two; neighboring Empung is young and is topped with a crater that stretches more than 1300 feet across and nearly 500 feet deep.
These two peaks are relatively inactive—it’s the double crater between them, Tompaluan, which keeps residents on their toes. Since the mid-19th century, Tompaluan has exploded in phreatic eruptions that are a mix of steam, water, ash, rock, and “volcanic bombs,”—hunks of molten rock that cool before landing. Tompaluan also produces the occasional lava flow.
This past month, the volcano began emitting a series of loud thumping noises and white plumes of vapor that rise more than 300 feet above Tompaluan crater, raising the volcano’s alert level to three (four means an eruption is eminent). Last week it let out an 8000-foot plume, and the government has begun to set up evacuation centers.
Italy’s Mount Etna
Mount Etna is one of the world’s most active volcanoes. It became notorious for a 1669 eruption that killed more than 20,000 people and dislocated thousands of others and, since then, Sicily’s 11,000-foot beast has put on a spectacular series of shows.
A stratosphere volcano, Etna has been spewing lava fountains (molten lava that shoots upward) and lava flows regularly for nearly a century. It’s also known to emit a film-noir-style smoke ring or two.
One reason Etna is so volatile: The volcano has six distinct craters at its summit where eruptions can occur. Eruptions also happen along Etna’s flanks, which sport more than 300 vents. While the summit eruptions put on visually stunning displays, it’s the flank eruptions that can cause the most damage because they’re closer to villages and often generate landslides.
Most recently, Etna has experienced frequent modest-size explosions accompanied by emissions of ash and lapilli, little molten stones, and sent forth incandescent ejections visible at night. The volcano has already erupted at least seven times in 2012.
Located on the edge of the Big Island in Hawaii Volcanoes National Park, 4190-foot Kilauea is both the world’s most visited volcano and the most dangerous volcano in the U.S. Hawaiian folklore considers Kilauea to be the body of the ancient volcano goddess Pele, and when she is angry, does she ever roar.
Kilauea produces a continuous flow of glowing molten lava that pours down its slopes and reaches the Pacific Ocean. The frequent eruptions are photogenic but destructive. Kilauea has destroyed nearly 200 structures since 1982, including some as recently as March.
Kilauea is one of five shield volcanoes—typically short and squat volcanoes built almost entirely of far-traveling, fluid lava flows—that together form Hawaii’s Big Island. It’s known for the production of mafic lava, a type of lava that’s less explosive than the more volatile felsic lava because it allows water and gases to escape. Kilauea’s volcanic plumes rise up from three locations: Halemaumau Crater, located within a caldera at her summit; Puʻu ʻŌʻō Crater, which has been continuously erupting since 1983; and along the Pacific coastline.
A March 2008 eruption has led to increasing concern about local air quality, most notably rising levels of sulphur dioxide and vog, a type of volcanic smog that often envelopes the island.
Though it lay dormant for many years, Tungurahua (“throat of fire” in the indigenous Quechua language) returned with a bang in 1999. The 16,480-foot stratovolcano spewed enough ash to force temporary evacuation of more than 25,000 nearby residents. Tungurahua has remained active since, including a series of major eruptions beginning in May 2006.
In August 2006, Tungurahua erupted with several pyroclastic flows—basically, swift-moving currents of gas and rock fragments that can reach temperatures exceeding 1830 F and speeds of 450 mph—killing at least five people and destroying small villages. Just last month, the volcano exploded with a series of cannon shots, gravel launchings, and high-rising steam plumes, causing local officials to raise the volcano alert level to orange (just below red, the signal for imminent evacuation). Constant cloud coverage around Tungurahua has made it difficult for scientists to determine the volcano’s current state.
Colombia’s Nevado del Ruiz
When Nevado del Ruiz blew in 1985, it wiped the town of Armero off the map, killing 25,000 people. Now the notorious 17,457-foot stratovolcano, situated about 90 miles west of the capital Bogotá in Los Nevados National Natural Park—is again showing signs of unrest.
Recently Nevado del Ruiz has been emitting rising levels of gas and sulfur along with a series of volcanic tremors, likely related to deep magma movements. The ominous signs, understandably, have residents on edge. Local officials have raised the volcano alert level in nearby towns and have fire departments ready for an imminent eruption.
Nevado del Ruiz typically generates plinian eruptions, which produce speedy pyroclastic flows and high-rising columns of gas and volcanic ash that look as though they’re ascending to the heavens. This type of explosion is marked by violent ejections of volcanic rock, continuous and powerful blasts of gas, and mud and debris flows called lahars that can wipe out entire towns.
In April 2010, Iceland’s Eyjafjallajökull ice cap erupted in a massive ash cloud, disrupting air travel across Europe and costing airlines hundreds of millions of dollars. But Eyjafjallajökull is one of the country’s smaller volcanoes. Experts say its neighbor, 4961-foot Katla, is the one folks should worry about.
Katla is an active subglacial volcano with a large ice-covered caldera (akin to a cauldron). Although it hasn’t had a significant eruption since 1918, Katla’s eruptions over the past 1000 years have typically followed those of Eyjafjallajökull. Since Eyjafjallajökull’s 2010 eruption, experts have noticed a rise in Katla’s harmonic tremor, a sustained release of energy often associated with magma moving beneath the earth’s surface or the release of volcanic gases. This is a sign of a possible upcoming eruption.
To provide some scope, Katla’s 1918 eruption produced five times the ash of Eyjafjallajökull’s 2010 eruption. So watch out.