According to the U.S. Department of the Interior(opens in new tab), there are around 1,350 “potentially active volcanoes” in the world, and little over one-third of them are known to have erupted at some point throughout historical records.
But where are the majority of volcanoes found? Where would you be most likely to discover an active volcano if you wanted to witness one?
Ed Llewellin, a professor of volcanology at Durham University in the United Kingdom, told Live Science via email that the majority of the planet’s volcanoes are situated underwater, along the mid-ocean ridge system, which is 65,000 km (40,000 miles) long.
The volcanoes along these ridges, which are normally 3 to 4 km [1.8 to 2.5 miles] below the ocean’s surface, produce around 80% of the Earth’s magma, according to him. All of the main oceans, including 16,000 km (9,900 miles) through the center of the Atlantic, are traversed by the ridge system, which extends for about 9,000 km (5,600 miles) into the eastern Pacific.
Llewellin said that because these volcanoes are buried deep inside the water, and as a result, their eruptions hardly ever have an impact on humanity, “it can be easy to forget about these volcanoes.” What about volcanoes located above the ocean’s surface, though?
Many of the on-land volcanoes are situated close to the Pacific Ocean, according to Llewellin. This is due to “subduction zones,” or regions along the margins of tectonic plates when one plate slides underneath another. They surround the Pacific Ocean.
The Pacific is home to the Ring of Fire, a 25,000 mile (40,000 km) long (opens in new tab), horseshoe-shaped, seismically active region that is the epicenter of around 90% of the world’s earthquakes and 75% of the world’s active land volcanoes (opens in new tab).
Old, cold, thick oceanic plates that surround the Pacific “slip below the nearby continental plates,” according to Llewellin. Since the minerals created at the ocean floor are released as the plates sink back into the mantle, the water that results melts the mantle above, creating magma.
Llewellin said, “The magma comes up from the mantle above the descending plate and makes its way through the supracontinental plate.” This explains why there are volcanic mountain ranges all around the Pacific, including the Aleutians between Alaska and Siberia, the Cascades in North America, and the Andes in South America.
According to Llewellin, the subduction zones in the western Pacific “mostly include one oceanic plate sliding below another oceanic plate.” It may also create large portions of Melanesia, a subregion of Oceania in the South Pacific that includes Fiji, Vanuatu, the Solomon Islands, and Papua New Guinea, as well as chains of volcanic islands, like the Japanese archipelago.
However, the Pacific has not always been a center for volcanic activity due to tectonic shifts. In fact, the extent of the global volcanic activity that was occurring 252 million years ago, when the Permian epoch gave way to the Triassic, would have made Earth far less livable. According to a 2017 study in the journal Nature, this period saw what is regarded as the biggest mass extinction event in history, with an estimated 96% of marine species and 70% of terrestrial life becoming extinct mostly as a result of intense volcanic eruptions (opens in new tab).
Volcanic eruptions aren’t as frequent today as they once were, which is fortunately for humans and the rest of the planet’s present population.
The majority of Earth’s volcanic activity has occurred outside the Pacific region, according to Llewellin, assuming we take into account undersea volcanoes along mid-ocean ridges. “Volcanic activity has gradually decreased in frequency over Earth’s history. We believe there may have been times when the whole surface of the Earth was covered in a magma ocean since the early Earth was much hotter than it is now.”
According to a 2021 research published in the journal Science Advances, “a deep sea of incandescent lava” sprawled over Earth’s surface 3.6 billion years ago, and “evidence of this red hot ocean is retained in the chemistry(opens in new tab) of ancient rocks from Greenland” (opens in new tab).
Llewellin described the idea known as the Big Splash, or the Theia Collision, saying, “The last time this happened was following the huge impact of a Mars-sized proto-planet, which led to the birth of the moon roughly 100 million years after the Earth originated.” “You might argue that the entire globe was a massive volcano during these magma ocean eras!”
Since the Earth is currently much colder and more habitable than it was during its seas of magma period, Llewellin predicts that volcanoes will eventually vanish from our planet as it continues to cool.
Llewellin said, “This has previously happened on the moon.” “As a result of its smaller size than the Earth, it cooled more quickly. The moon has been volcanically “dead” for around a billion years, although there was great volcanic activity there billions of years ago; the enormous dark regions we see are giant “seas” of hardened lava.”
Volcanoes are not going to vanish any time soon, though. Since the Earth’s core may not completely cool for 91 billion years(opens in new tab), volcanoes are expected to exist for far longer than humans and may even outlive the sun, which will probably perish in 5 billion years.
The finest place to travel to observe an eruption is Stromboli, a little island off the coast of Italy, according to Llewellin. “Almost continuously for the past 1,500 years, it has been erupting. A tiny explosion from one of the several vents at the volcano’s peak occurs every few minutes, and if you go on a guided tour up the volcano, you almost certainly will see one of them.”