Some volcanoes remain active for centuries because they are located above hotspots in the Earth's mantle, where heat and pressure cause the magma to melt and rise to the surface, continuously fueling volcanic activity.
Beneath our feet, the Earth remains a huge hot sphere, with a mantle located beneath the crust that contains a fluid rock called magma. In certain areas, this magma continuously rises to the surface because it is constantly supplied from reservoirs located deep within the Earth's mantle. These deep reservoirs thus ensure a kind of permanent renewal of fresh magma, supplying volcanoes for centuries without depleting. As long as this deep supply persists, the volcano never completely loses its activity and remains ready to erupt from time to time or to quietly release lava flows.
The Earth's crust is never truly motionless: it is divided into large rigid plates that slowly float on a viscous layer called the asthenosphere. These plates constantly move due to the convection currents in the Earth's mantle (imagine a thick soup heated from below, with warm bubbles rising and slowly sinking). As they move, the plates pull apart, collide, or slide beneath each other, creating cracks where hot magma can regularly rise to the surface. As long as these movements continue, the supply channels of the volcano remain open, keeping it active for centuries, or even longer.
Imagine under each volcano a true network of natural pipes. These are magma conduits, sometimes very branched and complex, that allow magma from the Earth's mantle to rise to the surface. Some of these conduits remain active for a long time because they do not easily become blocked. The more numerous, branched, and interconnected they are at depth, the more freely the magma can circulate. This creates a series of alternative paths: if one conduit cools and closes, there is always another route to feed the next eruption. As a result, some volcanoes can maintain their activity for centuries thanks to this stable and efficient underground network.
Beneath a volcano, the interaction between the hot magma rising from the depths and the solid rocks of the lithosphere plays a key role in the duration of its activity. When magma breaks through these rock layers, it exchanges heat and causes a chemical alteration of the surrounding rocks. This creates more fragile areas or, conversely, solid sections temporarily blocking the conduits. As a result, magma often changes paths, forming a true underground labyrinth of channels, ready to ignite at any moment. This complex network directly influences eruptions: as long as the magma-rock interactions persist, the volcano maintains all chances of remaining active for centuries.
A volcano can live multiple lives, alternating between periods of rest and sudden awakenings, and these cycles unfold over a very long timescale. Some well-known volcanoes remain active for thousands or even hundreds of thousands of years, like Mount Etna in Sicily. Why? In fact, their deep magma reservoir slowly but surely recharges, somewhat like a giant underground battery. The magma rises, but sometimes gets stuck, cools a bit, and patiently waits for its time before the next major eruption. These cycles of activity and rest can last for centuries, giving the impression that the volcano is eternally active. And even when it appears calm on the surface, it often continues to simmer discreetly underground, a simmering that can go incognito for a long time before a dramatic return.
Stromboli in Italy is one of the most active volcanoes in the world, and it has been erupting almost continuously for at least 2000 years!
Yellowstone, located in the United States, is a volcano in the form of a vast caldera that exhibits extremely long cycles of activity, lasting up to several hundred thousand years.
Some volcanoes are so active that they have created new islands, such as Surtsey Island in Iceland, which emerged after an eruption in 1963.
Volcanoes can influence the global climate: the eruption of Mount Tambora in Indonesia in 1815 caused what is known as 'the year without a summer,' leading to abnormally low temperatures across the planet.
Even though current technological advancements allow for detailed monitoring and help predict a certain intensity and likely duration of eruptions, it remains impossible to accurately forecast the exact time or magnitude of most eruptions due to the complexity of volcanic processes.
Not necessarily; it all depends on the historical behaviors of the volcano, the distance and density of surrounding settlements, as well as the type of volcanic activity. A volcano can remain active for a very long time without posing an immediate danger if it is monitored and its activity remains moderate or distant from populations.
Yes, some volcanoes such as Stromboli in Italy or Kilauea in Hawaii are known to have had nearly continuous activity for several centuries, with frequent gas emissions and lava eruptions.
An active volcano regularly shows signs of activity such as eruptions, tremors, or gas emissions. A dormant volcano hasn't erupted recently but could awaken in the future; on the other hand, an extinct volcano no longer has an active magma source underground and is therefore not expected to erupt again.
Scientists use various tools such as seismic stations, gas and temperature sensors, satellite and drone imagery, and GPS devices to detect ground deformations, as well as regular field observations to establish accurate long-term monitoring.
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