For hard evidence of nature’s ability to erupt into catastrophic disaster, look no further than the volcano. These metaphorical portals to hell, which currently number about 1500 globally, not only spew volcanic ash and lava, but can radically alter the climate and the course of world events.
Most are stratovolcanoes—cone-shaped elevations built over time from layers of ash and lava. Their relatively soft composition allows pressure to build up inside until they blow, resulting in explosive eruptions with little prior warning. Their steep slopes also generate mudslides and pyroclastic flows. All of these factors make them the most dangerous volcano type. (In contrast, shield volcanoes—like those in Hawaii—are low to the ground and often emit syrupy lava from vents in the Earth.)
Need examples? Look no further than these incendiary volcanic milestones, in no particular order.
1. Novarupta // Alaska
Volcanic eruptions can be measured in terms of consequences or simply in terms of sheer output. In the case of the latter, the Novarupta, or Katmai, eruption that began June 6, 1912, was a monumental event. Over 13 cubic kilometers of lava was released over the course of 60 hours, or the equivalent of 573.2 million tons every hour. In Kodiak, about 100 miles away, over 1 foot of ash collected on the ground. The cooled sheet of ash surrounding the volcano wound up forming the “Valley of 10,000 Smokes,” creating steaming fumaroles (openings in the ground where gas or water vapor escapes). The incident even prompted an atmospheric haze that was said to have reduced summer temperatures. All told, it was the largest volcanic eruption of the 20th century and earned a 6 on the Volcanic Explosivity Index (VEI), a measurement of the explosive thrust of an eruption, with 1 being least powerful and 8 being the most powerful.
2. Krakatoa // Indonesia
Indonesia holds the unwelcome distinction of hosting two of the most potent volcanic events of the 1800s. (Unfortunate, but understandable—its 150 active volcanoes are the most of any country.) One occurred in August 1883, when Krakatoa (sometimes spelled Krakatau) erupted on an island near Sumatra. Roughly five cubic miles of lava shot 50 miles into the air and ushered in massive tsunamis. The volcano gave off several warnings in the months leading up to its big burst, with a series of comparatively smaller explosions where the ash plume reached only seven miles into the sky. The first big blast, with a VEI of 6, came August 26, which demolished two-thirds of the island. Multiple eruptions followed, resulting in a global veil of ash that ultimately caused the planet’s temperature to drop by several degrees. About 36,000 people were killed, including 31,000 who perished when the tsunamis crashed into neighboring islands.
3. Mount Tambora // Indonesia
The mercilessness of volcanoes was on full and morbid display with Mount Tambora, which blew in April 1815 in Sumbawa, Indonesia. In the days before the blast, which had a VEI of 7, nearby soldiers heard cannon-like rumbling and armed themselves, thinking an enemy was about to attack. In a way, one was. Tambora spewed 12 cubic miles of gases and dust 25 miles into the atmosphere, triggering towering tsunamis and drenching the surrounding islands in ash. Roughly 10,000 people perished immediately, and a total of 90,000 died due to resulting food shortages. Today, scientists believe the epic eruption may have radically altered global weather, leading to crop failures and famine in North America and Europe. In 1816, with Tambora's ash still blanketing the skies of the Northern Hemisphere, the poet Lord Byron challenged his literary friends, including Mary Shelley, to write something appropriately macabre. She began Frankenstein.
4. Mount St. Helens // Washington
Volcanic terror hit North America on May 18, 1980, when Mount St. Helens blew its top. Days earlier, an earthquake had prompted avalanches on the volcano. Thousands of earthquakes followed, which destabilized the terrain. Then, a 5.1-magnitude earthquake hit, causing the peak to blow ash and hot gases skyward. The blast took an incredible 1314 feet off the height of the mountain. Effects were felt and seen across 230 square miles, and 158 miles of highway were damaged. Recovery from the disaster cost over $1.1 billion. With 57 people killed, Mount St. Helens's explosion—with a VEI of 5—remains the deadliest volcanic eruption in U.S. history.
5. Mount Vesuvius // Italy
While not quite on the level of other massive eruptions (it's only a 5 on the Volcanic Explosivity Index), the lore surrounding the rage of Mount Vesuvius puts it in a category all its own. The volcano exploded on August 24 in the year 79 CE, turning the Roman cities of Pompeii and Herculaneum into frozen portraits of thousands of interrupted lives. Before being blanketed in ash, Pompeii was known for fertile ground that fed orchards and vineyards; Herculaneum was a summer getaway for the Roman elite. When Vesuvius erupted, many stayed behind hoping to wait it out. But another blast gassed and incinerated the cities, then buried them in mud and ash. The cities were rediscovered in the 18th century, and new discoveries about the last days of Pompeii and Herculaneum are still being made.
6. Mount Pinatubo // Philippines
A colossal volcanic eruption—6 on the VEI—of recent vintage, Mount Pinatubo caused cataclysmic destruction of a thickly populated part of Luzon in the Philippines on June 15, 1991. After a series of earthquakes and a stream of magma making its way 20 miles upwards to the surface of the Earth, Pinatubo's activity crescendoed when gas-powered lava, totaling more than five cubic kilometers, was released. Pyroclastic flows of ash and pumice left deposits over 660 feet thick at the foot of the mountain, while tropical storms created vast mudslides out of the volcanic ejecta. Heavy layers of wet ash crushed buildings. Fortunately, scientific forecasts were able to warn residents, who were evacuated; thousands of lives were saved.
7. Laki // Iceland
For sheer stubbornness, few volcanic eruptions beat Laski, located in what is now Vatnajökull National Park in Iceland. Instead of one giant eruption, Laki perpetuated a series of lava flows and explosions that lasted for more than eight months in 1783 and 1784 and registered a VEI of 4. Laki produced enough lava to pave the entire city of Boston 207 feet deep. The eruption emitted gases that resulted in acid rain strong enough to burn leaves and irritate skin, while the toll on livestock caused a famine that may have killed up to one-quarter of Iceland’s population at the time. Like the aftermath of Tambora's eruption, Laki's ash veil caused widespread weather disruption and food shortages in Europe. It may have even fueled the unrest that preceded the French Revolution.
8. Mount Pelée // Martinique
Mount Pelée loomed over the quiet hamlet of St. Pierre, on the French Caribbean island of Martinique, like a ticking time bomb. In early May 1902, a violent lahar—a river of volcanic rock fragments and water—burst out of the side of the mountain, inundating a sugar refinery before reaching the sea and triggering a tsunami. The disturbances caused wildlife—huge insects and venomous snakes—to flee the mountains and seek safety in the town. Bites from vipers killed about 50 people. But the island's governor assured residents that there was no real danger. Unfortunately, he was extremely wrong. On May 8, the mountain exploded with a VEI of 4, unleashing a blast of superheated gas and debris that destroyed St. Pierre and killed 30,000 residents in just a few minutes.
9. Nevado del Ruiz // Colombia
At 77 square miles, Nevado del Ruiz is an imposing stratovolcano. It has erupted several times since 1570, but the most memorable event occurred November 13, 1985. As magma bubbled up toward the volcano's apex, the heat melted huge glaciers that blanketed the peak. The rivers of melted ice became devastating lahars, which joined up with existing rivers to cause catastrophic mudslides in the valleys. During the VEI 3 eruption, the nearby town of Armero was flattened and 23,000 people lost their lives in the floods.
10. Mount Tarawera // New Zealand
The people inhabiting North Island in New Zealand got a seismic shock on June 10, 1886, when Mount Tarawera erupted, forming fissures in the Earth that extended 10 miles from the epicenter. The VEI 5 blasts were heard up to 310 miles away, making it the largest volcanic event in New Zealand’s history. It also has some ghost stories attached to it. Some European residents insisted they saw a Māori war canoe sailing on Lake Tarawera just before the eruption. They hailed the sailors, but they didn't respond. Later, after the cataclysm, the observers learned no such canoe had ever been seen on the lake.
11. Yellowstone // Wyoming
Beneath the grounds of Yellowstone National Park lurks a supervolcano, one that’s believed to have erupted substantially at least three times in recorded human history: 2.1 million years ago (which had a VEI of 8), 1.3 million years ago, and 664,000 years ago. The last left a depression in the ground 34 miles by 50 miles in size. Today, the magma underneath Yellowstone is five miles deep, prompting some to speculate that if it ever erupted—and there’s a non-zero chance of that happening—it could bury the Rockies in ash, thanks to its potential for unleashing a super-eruption (anything with a VEI of 8 or higher).