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While active volcanoes capture most of the attention with their spectacular eruptions and apocalyptic destructive potential, some of the world’s most massive volcanic behemoths currently lie dormant. Hushed for now, these towering peaks stand in silent dormancy after epochs of eruptive cycles that shaped the surrounding landscapes. Here we look at the most gigantic of these sleepers that could potentially reawaken:
Yellowstone Caldera, United States
Overshadowing all other dormant volcanoes in size is the massive Yellowstone caldera spanning a 30×45 mile area in northwestern Wyoming. This gargantuan volcanic depression formed during the last of three mind-bogglingly huge eruptions that occurred 2.1 million, 1.3 million and 630,000 years ago respectively. The youngest cataclysmic blast expelled over 240 cubic miles of debris across much of North America. While Yellowstone’s slumbering giant shows signs of semi-regular disturbances like hydrothermal explosions and ground uplift, the USGS estimates the odds of a full-blown eruption within the next few thousand years are exceedingly slim.
Taupo Volcanic Zone, New Zealand
Located in New Zealand’s North Island, the Taupo Volcanic Zone is a highly active hotbed that has produced the two most powerful volcanic eruptions anywhere on Earth over the past 70,000 years. The deadly Oruanui eruption around 26,500 years ago expelled a mindboggling 120 cubic miles of material, while the more recent Hatepe eruption around 232 AD still ranks as the most violent over the past 5,000 years. Permanent settlement in the region is inadvisable given the likelihood of future high-magnitude eruptions originating from the currently dormant caldera complexes.
Ngorongoro Crater, Tanzania
Widely considered one of the largest intact calderas in the world, Ngorongoro Crater formed around 2.5-3 million years ago during an epic eruption that saw the entire volcano collapsing inwards on itself. The resulting 2,000-foot-deep crater now provides a remarkably fertile ecosystem for one of the highest concentrations of wildlife in Africa to thrive. While Ngorongoro is currently dormant, the crater does exhibit fumaroles signaling that volcanic activity could potentially resume at some point in the violent future. The adjacent Olmoti and Empakaai craters also formed relatively recently in geologic timescales around 8,000 years ago.
Anahola Volcano, Hawaiian Islands
Though often overshadowed by its more famous cousins Mauna Kea and Mauna Loa, the ancient Anahola volcano is considered one of the largest shield volcanoes on the planet in terms of sheer mass. Rising 15,400 feet from the seafloor, Anahola first began erupting around 5 million years ago before becoming extinct around 3.5 million years ago after violently explosive eruptive cycles. The volcano’s elongated shape is thought to have formed from the dynamic shifting of the Pacific tectonic plate during its lifespan. While dormant for millions of years, monitoring shows magma may persist within its volcanic plumbing system.
Elbrus, Russia
At 18,510 feet, the towering dormant Elbrus volcano is not only the highest peak in Russia but the entire European continent. This massive stratovolcano is considered a “semi-dormant” volcano having experienced infrequent weak eruptions over the past few centuries. Its broad slopes are blanketed by vast glaciers formed from millennia of volcanic ash accumulation mixed with snow. While Elbrus is not expected to erupt catastrophically anytime soon, its flanks remain a potential hazard zone for mudflows and debris avalanches triggered by rising temperatures destabilizing the glacial ice caps.
Cotopaxi, Ecuador
One of the highest active volcanoes in the world, Ecuador’s Cotopaxi stands an imposing 19,347 feet tall and has remained dormant since its last major eruption in 1904. Cotopaxi is considered among the world’s most threatening volcanoes given its lengthy history of explosive eruptions, proximity to heavily populated areas, and generation of devastating lahars and landslides when eruptions melt portions of its massive glacial icecap. Increased seismic activity in recent decades has raised concerns about a potential reawakening, which could prove utterly catastrophic for nearby cities like Quito.
Bárðarbunga, Iceland
One of the highest-risk volcanic systems in Iceland, the massive subglacial Bárðarbunga volcano encompasses a 200 square km caldera hidden beneath the Northwestern Vatnajökull ice cap. Its huge 2014-2015 eruption was the largest in Iceland in over 200 years, releasing enough sulphur dioxide to cause air pollution across much of Europe. Despite being currently dormant, Bárðarbunga remains highly volatile given its tendency for large-volume eruptions of fluid basalt from its central volcano as well as surrounding fissure vents, which could quickly melt overlying glaciers and trigger catastrophic outburst floods.
Ulawun, Papua New Guinea
Towering over 8,000 feet high, Ulawun is one of the most hazardous volcanoes in the Southwest Pacific region due to its frequent emissions of ash and volcanic gases from its exposed summit crater. The large stratovolcano has experienced no fewer than 23 major eruptions since the 18th century, with the 2019 event spewing ash as far as 60 miles away from the remote island it occupies in the Bismarck Archipelago. While currently dormant, Ulawun’s pattern of intermittent violent activity raises concerns about the potential for future explosive events sending deadly pyroclastic flows into surrounding areas with little warning.
Iriga, Philippines
The little-known Iriga volcano in the Philippines’ Bicol region produced one of the largest eruptions in recorded history around 1628, ejecting over 2 cubic miles of dense rock and ash. Geologists believe the tephra from this singularly massive VEI 6 eruption buried much of the surrounding countryside under meters of volcanic debris. Despite this cataclysmic event, the 5,142 ft stratovolcano has remained dormant in modern times and is now heavily eroded and obscured by dense jungle vegetation. However, its long-dormant state belies its potential to awaken with little notice and reproduce its past deadly explosivity.
Galunggung, Indonesia
Situated near the city of Tasikmalaya in West Java, the Galunggung volcanic complex includes at least 5 overlapping summit craters along the spine of its towering 7,052 ft peak. Following several centuries of dormancy, a sudden explosive eruption in 1982 ejected over 120 million cubic meters of ash across a widespread area, causing considerable destruction and killing dozens of people. While currently quiet, Galunggung remains one of Indonesia’s most hazardous volcanoes due to its propensity for infrequent but violent eruptions after extended periods of repose when monitoring is minimal. Its current slumber could prove treacherous for surrounding populations if a reawakening occurs with little warning.
These immense dormant volcanoes may appear as serene giants in their current states. However, their track records amply demonstrate how extraordinarily destructive they can be when roused from their long volcanic slumbers by the restive forces brewing miles beneath the Earth’s surface. Constant geological vigilance is crucial to avoid complacency around these potential powder kegs waiting to be relit.