News of volcanic eruptions only reaches the headlines when the big ones erupt — Etna, Kilauea, Mauna Loa, Merapi, Eyjafjallajökull or Fagradalsfjall — but at any time during a given year, there may be as many as 50 to 80 fresh eruptions around the world.
Data from the Smithsonian Institution's Global Volcanism Program suggests that 56 volcanoes erupted in the first six months of 2023.
In November 2023, shifting magma under the Earth's crust triggered hundreds of earthquakes around the town of Grindavik in Iceland, with seismologists warning the quakes could be a precursor to a volcanic eruption.
Italy's Mount Etna, which is one of the world's most active volcanoes, was causing public concern as well — it started erupting the year before. So, let's take a closer look at Etna.
How long has Mount Etna been an active volcano?
Mount Etna is Europe's most active volcano and one of the largest in the world. Its recorded volcanic activity dates back to 1500 B.C. Since then, it has erupted more than 200 times.
The current eruptions at Etna have led to flight cancellations at nearby Catania airport.
The use of cars and motorbikes has also been banned for 48 hours due to high amounts of ash on the roads. Ash can be slippery and increases the risk of accidents.
Other volcanoes erupt for much longer than Etna
One of the most famous long-term eruptions was Kilauea volcano on Hawaii. Its spewing spree in 1983 continued — almost nonstop — for 35 years until 2018, only to start again in 2021. The eruption is still ongoing.
Dukono in Indonesia started erupting in August 1933 and is still continuing. Santa Maria in Guatemala began erupting in June 1922 and continues to this day.
And Yasur in Vanuatu first rumbled to life in about 1270 (± 110 years) and as of June 9, 2023, was still erupting.
What is a volcano?
The US Geological Survey sums it up nicely: "Volcanoes are openings, or vents where lava, tephra (small rocks), and steam erupt onto the Earth's surface."
Volcanoes can be on land and in the ocean. They are, in part, a result of their own eruptions but also the general formation of our planet, as tectonic plates move.
Mountain ranges like the Andes in South America and the Rockies in North America, as well as volcanoes, formed through the movement and collision of tectonic plates.
There are four main types of volcanoes: cinder cones, composite or stratovolcanoes, shield volcanoes and lava domes.
Their type is determined by how the lava from an eruption flows and how that flow affects the volcano, and, as a result, how it affects its surrounding environment.
How do volcanoes erupt?
Essentially, it's a case of magma, or molten rock, below the surface of the Earth, bubbling up, rising and overflowing, like boiling milk out of a pot on a stove.
The magma finds its way to vents in the volcano and gets spewed across the land and into the atmosphere. When magma erupts from a volcano, it is called lava.
Volcanoes particularly active in Pacific Ring of Fire
Some of the most active volcanoes are located in the Pacific Ring of Fire, which includes New Zealand, Southeast Asia, Japan and the western coast of the Americas. About 90% of all earthquakes worldwide strike within this region.
Can scientists predict volcanic eruptions?
Scientists are capable of predicting volcanic eruptions hours, or sometimes several days, in advance. This isn't the case with earthquakes, which are much harder to predict.
Scientists use seismographic data from earthquakes and other tremors, because those can be a precursor to volcanic eruptions.
They monitor the ground for signs of deformation, which may be caused by the movement of magma. They also take readings of volcanic gas emissions, and changes in gravity and magnetic fields.
Edited by: Fred Schwaller