Kamal Ghorui
For years, the Methana volcano located in Greece has been categorised as a dormant volcano since it has always appeared peaceful and inactive due to its proximity to the Saronic Gulf in the vicinity of Athens. It had always been assumed that it did not display any signs of volcanic activity for hundreds of years, but current findings by scientists have proven that it was just a misconception. Geological studies reveal that there were times when the volcano maintained surface tranquillity for decades, during which time magma accumulated below the surface of the Earth.
Greece’s Methana volcano reawakens after 100,000 years of hidden magma activity
The last recorded volcanic eruption of Methana took place in approximately 250 BCE. It was noted in several ancient Greek texts, and ever since, there has not been any surface activity of the Methana volcano. As such, its relative peacefulness led to an assumption that it poses no threat to humans.According to the study published in Science Advances, titled ‘A volcano reawakens after more than 100,000 years of “silent” magma reservoir growth’, modern scientists claim that this notion is wrong. Scientists from ETH Zurich conducted a thorough study on the geology of Methana and discovered something quite unexpected. For the past 700,000 years, the Methana volcano has undergone numerous stages of volcanic activity separated from each other by long quiet periods.One of the most intriguing discoveries was the period when Methana did not demonstrate any activity on the surface for about 100,000 years, but was anything but quiet inside the Earth.
What zircon crystals reveal about Methana’s hidden underground activity
For understanding the history of Methana, studies were carried out on over 1,250 zircon crystals obtained from ancient volcanic rock flows. Such crystals develop in magma and can retain information about geological processes for a long time. The study of the process of radioactive uranium degradation allows for estimating the time of the eruption.It turned out that even in those times when there were no eruptions of the volcano, zircon formation was active. It indicates that there was magma movement under the volcano. Scientists assume that Methana was not dormant during that period but passed into a state where magma accumulation was taking place underground, but it did not come to the surface.
Why magma can stay trapped underground
Methana is located on top of a subduction zone, whereby one plate moves underneath another. The melting of some parts of the sea floor creates magma, which then moves up towards the surface. Unlike other magmas, this particular magma is exceptionally full of water.When magma that is very watery moves up, the gases start forming due to the reduction in pressure. In many ways, the magma resembles soda since the gases will create bubbles, causing it to become very thick. The magma does not rise to the Earth’s surface; instead, it gets stuck within the Earth. As a result, there is the creation of magma chambers deep within the volcano.
Methana study suggests some “extinct” volcanoes may still be active underground
Typically, extinct volcanoes have been defined as those that have not erupted within the past 10,000 years. The history of Methana poses a challenge to this definition. It takes up to 100,000 years before a volcano enters a period of silence, which indicates that periods of dormancy do not mean the volcano is extinct.It has been speculated that there is a possibility that volcanoes that have been defined as extinct might actually have active magma chambers beneath their surfaces. Such a magma chamber could simply be in dormancy and requires certain circumstances to erupt.
