The Most Dangerous Volcanoes in the World
Volcanoes can unleash hellish fire and ash that threaten the lives of people, animals and vegetation. When a volcano explodes magma that originated far beneath the surface rises, pushing though weak spots in the Earth's crust.
To determine the most dangerous volcanoes, experts ranked each based on population density, types of eruptions and history. Here are the top 10.
1. Popocatepetl Volcano
The towering snow-capped volcano Popocatepetl (Pop-o-ca-te’-pet’-ul), which looms over Mexico City and Puebla, has been spewing toxic fumes, ash and lumps of incandescent rock for nearly 27 years since awakening from a long slumber. But it’s not a matter of if the volcano will explode, but when.
The volcano’s proximity to two of the world’s most populated cities makes it one of the most dangerous in the world. According to experts, an eruption of the volcano would essentially spell disaster for about 23 million people.
When an eruption occurs, the resulting volcanic hazard is measured by a scale called VEI (Volcano Explosivity Index). The higher the VEI, the more severe the volcano. Popocatepetl has a VEI score of 4, meaning it’s capable of throwing lava and rocks up to 1 kilometer high.
In the past, Popocatepetl has erupted mostly andesitic lava, but this eruption has been producing a mix of andesitic and dacite lava. The lava is also relatively fluid, meaning it could move fast and displace residents in the surrounding area.
But Carlos Valdes Gonzalez, a volcano researcher with the IGEF, points out that not all volcanic activity is necessarily bad. For example, the land around the volcano is very fertile, thanks to its volcanic soils. And its height plays a critical role in the region’s weather patterns, helping to bring in rain.
2. Galeras Volcano
Galeras is a massive volcano located in southwestern Colombia, near the city of Pasto. It is a well-studied volcano and predictions of eruptions have improved over time. One phenomenon that seems to be a reliable precursor is a low-frequency seismic event called a tornillo. These events occur before about 80% of the explosions at Galeras and seem to correlate with the size of the ensuing eruption.
On January 17th 2008, a phreatic eruption of Galeras took place. The eruption produced a lava dome and pyroclastic flows. This eruption was accompanied by a four-fold increase in the number of daily long-period earthquakes.
The eruption is believed to have been triggered by gas build-up in the crater and the collapse of the western wall of the caldera. It was the largest eruption at Galeras since 1988.
A large lava dome continues to grow inside the crater. The dome has been a source of periodic explosive eruptions and has also caused lava flows.
The Galeras volcanic complex is a part of the Pacific ring-of-fire. It formed from the collision of the Panamanian tectonic block and South America’s Nazca plate. The volcano is one of many in the Northern Andes mountain range that stretches across southern Colombia, north into Ecuador and east toward the Pacific coast. Its close proximity to the city of Pasto makes it one of the most dangerous and potentially disastrous volcanoes in Colombia.
3. Mount Pinatubo
Located in the Zambales Mountains of the Philippines, Pinatubo is best known for its 1991 eruption, the second-largest volcanic explosion ever recorded. Its effects were felt worldwide, dropping global temperatures and leaving behind a layer of sulfuric acid haze. Prior to that eruption, the volcano was relatively inactive and largely unmapped because it was heavily eroded and covered in forests.
In March 1991, frequent earthquakes shook the region, and scientists from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) quickly rushed to the volcano. They set up seismometers, a tiltmeter to monitor deformation of the volcano, and a spectrometer to track gases such as sulfur dioxide. The spectrometer showed dramatic increases in gas production, which, along with increasing seismicity and tiltmeter readings, indicated magma was moving inside the volcano.
The scientists were right. An eruption followed shortly after, sending lava bombs and pyroclastic flows down the mountain’s sides. The blasts threw volcanic material up to 19 kilometres (62,000 ft) above sea level, and ash clouds reached even farther. The volcano’s eruption caused the deaths of 722 people, many of them from a combination of falling debris and disease spread in evacuation camps.
The eruption also melted snow on the mountain, which made its way to villages below the volcano and contributed to mudflows that killed more than 300 people. That was just the beginning of a series of eruptions that lasted more than a month and deposited up to 100 million tonnes of pumice and tephra.
4. Mount St. Helens
The smoky volcano that famously blew its top in 1980 isn’t one of the world’s most dangerous because it killed only 61 people, but rather because it’s so close to cities. In fact, it’s so close that a sudden eruption would wreak havoc on Seattle and its suburbs.
The volcano also has weak slopes which means that any eruption will cause landslides. Adding to the problem is that St. Helens is a stratovolcano which is capable of erupting much more violently than shield volcanoes like Hawaii’s Kilauea.
Volcanoes don’t just rumble and spew lava – they often release a gas called sulfur dioxide that smells bad. The concentration of sulfur dioxide varies, depending on what the volcano is doing, but a large eruption can send the gas into the atmosphere and create a thick haze that causes breathing problems.
Several of the volcanoes that made the list last year failed to make it this time, thanks in part to better dating techniques that have pushed back the date of their last eruptions past 11,700 years. However, many still pose a threat to the world’s population and should be watched closely. In addition to those listed above, Wyoming’s Yellowstone supervolcano and New Mexico’s Valles caldera also figured in the rankings. They are considered a threat to human life because the gases they release could affect the climate.
