Mount Vesuvius, on the Bay of Naples, Italy, brings to mind the cities of Pompeii and Herculaneum buried in ash, their inhabitants frozen in time and place as they tried to escape one of nature’s most powerful and destructive forces. Volcanoes such as this and the more recent Mount St. Helens in Washington state devastate entire regions, kill those unlucky enough to be in the paths of pyroclastic flows, and cause astronomical financial loss.
These eruptions are mere hiccups to what lies beneath the ground in some of the most populated countries in the world, including the United States. The existence of supervolcanoes isn’t widely known by the general population, but they have caused extinction level events throughout Earth’s history. What causes these sleeping giants to erupt remains a mystery, and luckily for humanity they are rare. When they do blow, the largest threat is volcanic ash consisting of microscopic glass and rock particles which can cover thousands of square miles and disrupt weather patterns worldwide.
Mt. Tambora located on Sumbawa Island, Indonesia is the most recent of eruptions classified in the titanic range at a Volcanic Explosivity Index, or VEI, scale of 7 (8 is the highest.) Though typically supervolcanoes must have a VEI of 8, Mt. Tambora certainly deserves an honorable mention considering the devastation it wrought. In 1812, eruptions began, and by April 1815, catastrophe struck. The explosions from the volcano could be heard 1,600 miles away which roughly equates to standing on your front porch in Kansas City, Missouri and hearing an explosion in Los Angeles, California.
The following summer of 1816 is widely known as the year without a summer, thanks to global climatic changes resulting in a volcanic winter. Around 71,000 people died either directly from the volcano, or from the resulting environmental changes that caused disease and starvation throughout the world. Mt. Tambora is still active to this day.
A supervolcano on Lake Toba, Sumatra, Indonesia erupted some 74,000 years ago and caused the largest eruption known in the last 25 million years. Pyroclastic flows destroyed 7,700 square miles. By comparison the state of New Jersey is 8,722 square miles. Parts of Indonesia were covered in a blanket of ash 20 feet deep, while areas of Malaysia lay beneath 30 feet. As far away as south Asia lay buried beneath nearly six inches of ash. The caldera left behind measures 1,080 square miles.
Following the massive eruption, global temperatures fell by as much as 28 degrees F in higher latitudes. Humanity went into a genetic bottleneck with only a few thousand breeding pairs during the long cold snap that followed, whether directly related to the volcano is still under debate. Earthquakes of magnitudes eight or more still rock the Lake Toba region today, and smaller volcanic eruptions occur off and on. When another super event could occur is anyone’s guess.
Long Valley Caldera in eastern California hosted its own mega-colossal eruption 760,000 years ago that unleashed 3,000 times more ash and lava than Mount St. Helens. The base of the caldera dropped a mile afterwards, and ash blasted 25 miles into the air settled as far away as eastern Kansas. The last eruption, though small, was 250 years ago. Recently the 200 mile caldera has shown signs of life once more. Earthquake swarms plagued the area in 1980, raising the caldera floor by 10 inches for 100 square miles. In the 1990’s, carbon dioxide began seeping from underground magma chambers, killing off trees in the Mammoth Mountain region of Long Valley. Scientists are watching the area closely and working with local residents and authorities; these signs could mean another volcanic eruption is a few years or a few centuries away.
Lake Taupo in New Zealand has had mega-violent episodes for the past 65,000 years. The caldera itself is an impressive 485 square miles. Its last eruption was 181 A.D., at a hundred times the strength of Mount St. Helens, though 26,500 years ago a magnitude VEI=8 eruption hit. Ash over 600 feet deep covered the northern region of the country, which would equal a 55 story building. Lake Taupo is still geologically active and powers a geothermal energy plant that generates a small portion of New Zealand’s electricity.
Valles Caldera, New Mexico last erupted 1.2 million years ago, sending ash as far away as Iowa. As short as 60,000 years ago, it spewed lava that built mountains and left obsidian flows. Today hot springs dot the caldera and whether or not it’ll erupt once more is unknown.
What most Americans don’t realize is that Yellowstone National Park is actually a giant, active volcano, evident by the thousands of geysers, bubbling mud pits, hot springs and steam vents. The caldera alone is 1,500 square miles and its last titanic eruption 640,000 years ago sent out 8,000 times more ash and lava than Mount St. Helens, leaving most of North America covered in ash inches deep as far away as the Gulf of Mexico. Areas within 3,000 square miles of the volcano were obliterated under pyroclastic flows. Even this isn’t the most powerful eruption in its history.
Earthquake swarms have plagued the area, and a notable bulge beneath the land has left scientists concerned. They are closely monitoring the land as well as the magma chamber’s depth. What’s more of a worry are the hydrothermal, or steam, explosions that have left twenty big craters over the park for the past 14,000 years. Though they are independent of the volcano, they could potentially harm people and wildlife in the area. The largest is 1.5 miles across and formed 13,800 years ago.
The calderas left behind by these gigantic explosions are now some of the most breathtaking natural areas on earth. While enjoying their beauty, it’s important to remember how they formed. If another of these sleeping giants comes to life, it could very well mean the end for humans, especially if not prepared well in advance.
