5. Taupo Caldera
New Zealand’s Taupo caldera has been filled by water, creating what many describe as one of the world’s most beautiful landscapes.
Lake Taupo itself was created by a massive eruption 26,500 years ago. The caldera — the collapsed and subsided basin left after the huge eruption — became today’s lake. But Taupo did not die. The 485-square-mile caldera let loose again in the year A.D. 181, with estimates of ash and magma reaching as high as 22 cubic miles. That’s on the order of a hundred times more than Mount St. Helens. Today Lake Taupo still shows signs of life, which New Zealanders have put to good use. Ample hot springs and other hydrothermal activity enable New Zealand to generate about 8 percent of its electricity at a geothermal plant on the north side of Lake Taupo, at Wairakei.
4. Valles Caldera
The 175-square-mile Valles caldera forms a large pock in the middle of northern New Mexico, west of Santa Fe. It last exploded 1.2 million and 1.6 million years ago, piling up 150 cubic miles of rock and blasting ash as far away as Iowa. As with other calderas, there are still signs of heat below: hot springs are still active around Valles. Geologists suspect the cause of Valles caldera has something to do with how the western United States’ portion of the North American tectonic plate is being pulled apart.
3. Long Valley, California
Second only to Yellowstone in North America is the Long Valley caldera, in east-central California.
The 200-square-mile caldera is just south of Mono Lake, near the Nevada state line. The biggest eruption from Long Valley was 760,000 years ago, which unleashed 2,000 to 3,000 times as much lava and ash as Mount St. Helens, after which the caldera floor dropped about a mile, according to the U.S. Geological Survey.
Some of the ash reached as far east as Nebraska.
Long Valley’s most recent eruption was in Mono Lake just 250 years ago, but it was very small. More worrisome is a swarm of strong earthquakes in 1980 and the 10-inch rise of about 100 square miles of caldera floor. Those developments have geologists concerned that Long Valley is gearing up for another eruption of some sort.
In the early 1990s yet another subtle sign of trouble became evident: Large amounts of carbon dioxide gas from magma below had begun seeping up through the ground and killing trees in the Mammoth Mountain part of the caldera. When these sorts of signs are present at a “central vent” volcano like Mount St. Helens, trouble is on the way soon. At a caldera, which has many outlets, it could mean trouble is years, decades or even centuries away, say volcanologists.
2. Lake Toba
The 1,080-square-mile Toba caldera is the only supervolcano in existence that can be described as Yellowstone’s “big” sister.
About 74,000 years ago, Toba erupted and ejected almost three times as much volcanic ash as the most recent major Yellowstone eruption (Lava Creek, 630,000 years ago) and about 12 percent more than Yellowstone’s largest eruption (Huckleberry Ridge, 1.8 million years ago). That comes to several thousand times more material than erupted from Mount St. Helens in 1980.
Some researchers suspect that Toba’s super eruption and the global cold spell it triggered might explain a mystery in the human genome. Our genes suggest we all come from a few thousand people just tens of thousands of years ago, instead of from a much older, bigger lineage — as the fossil evidence testifies. Both could be true if only a few small groups of humans survived the cold years following the Toba eruption.
1. The Yellowstone Caldera
Unbeknownst to most, Yellowstone National Park sits on a subterranean chamber of molten rock and gasses so vast that it is arguably one of the largest active volcanoes in the world. A magma chamber not far below the surface fuels all the volcanic attractions that Yellowstone is famous for. The last major eruption at Yellowstone, some 640,000 years ago, ejected 8,000 times the ash and lava of Mount St. Helens. Catastrophic eruptions occur at Yellowstone approximately every 600,000 to 800,000 years. Two of those eruptions are among the largest eruptions known to have occurred on Earth, each more than 1,000 cubic kilometers in scope. There have also been around 30 smaller eruptions, the most recent of which was 70,000 years ago.
If another caldera-forming eruption occurs, it’s estimated that the explosion would be equivalent to a force a thousand times more powerful than the Mount St. Helens eruption in 1980. The after-effects would be felt around the planet, with ash deposits dumped in 10-foot layers up to 1,000 miles away, and gases released into the atmosphere, dramatically affecting the global climate. Two-thirds of the U.S. could become uninhabitable as toxic air forces millions from their homes. Although scientists feel that the odds are good that such an eruption won’t happen within the next few thousand years, smaller and less damaging lava flows are possible.