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The Earth, a colossal sphere of semi-molten rock, harbors a fiery core as hot as the Sun's surface. Within its depths, heat from its birth and the decay of radioactive elements races towards the surface, channeled by rock currents spanning thousands of miles. The Earth's crust, a fragile shield against this inferno, is the only barrier standing in their way. But what happens when this shield is breached? Enter the supervolcanoes.
Have you ever wondered how big these supervolcanoes can get, and whether they pose an existential threat to humanity? Unlike the towering mountains and lava domes we often associate with volcanoes, supervolcanoes originate from two primary sources: the boundaries between tectonic plates and mantle plumes. The former are the pieces of the Earth's crust that move at a snail's pace, shaping mountains and ocean trenches. The latter are columns of extremely hot rock rising from the core-mantle boundary to the surface.
At the boundaries of tectonic plates, the winning plate rises to form new mountain ranges while the loser is pushed beneath the Earth's surface into the hot rock soup of the asthenosphere. Here, water triggers chemical transformations, allowing tiny portions to melt into magma. This magma, being less dense than solid rock, bubbles up to the surface, forming volcanoes. Meanwhile, mantle plumes rise from the depths, defying the movement of tectonic plates and creating isolated volcanoes that stubbornly stay active as the crust shifts around them.
Scientists have devised a logarithmic scale to measure volcanic eruptions: the Volcanic Explosivity Index (VEI). A VEI 2 eruption would fill hundreds of Olympic swimming pools with lava, while a VEI 5 eruption would blast cubic kilometers of debris into the air. At a VEI of 6, an eruption can alter the world, as seen in the 1883 eruption of Krakatoa. And then there are the VEI 7 Super-Colossal eruptions, events so powerful they redefine entire millennia.
Though the term "super volcano" is a media invention, it refers to a specific type of volcano that has been lying dormant for hundreds of thousands of years. Pressure builds up in colossal magma reservoirs until it becomes strong enough to crack the rock above, unleashing a supersonic explosion of gas and ash. These super eruptions, while only releasing a small portion of the magma reservoir, leave behind a caldera and trigger a new cycle of pressure buildup for the next eruption.
The most recent super eruption was the Oruanui eruption 26,500 years ago in New Zealand, which triggered a period of abrupt cooling in the Southern Hemisphere. The Lake Toba eruption of 74,000 years ago was even more significant, blanketing parts of South Asia in ash and causing a 4°C drop in global temperatures. These events, while not as explosive as some eruptions, have shaped our planet's climate and history.
Despite their potential destructiveness, supervolcanoes are not an impending apocalypse. The most famous one, Yellowstone, will erupt again, but it will likely be a relatively small eruption. The chance of a VEI 8 eruption in the next few hundred years is less than 2%, and even then, it would not come as a sudden surprise.
While we must remain vigilant and monitor slow changes in magma reservoirs, there is time to develop solutions that can mitigate the impact of volcanic eruptions. By removing sulfur and ash from the stratosphere, we can eliminate the root cause of climate disruption caused by previous eruptions. Perhaps we can even harness the geothermal energy stored in these magma reservoirs for the greater good.
So, while an angry hell churns deep beneath our feet, rest assured that humanity has the determination and ingenuity to tackle whatever challenges lie ahead.
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