Sicily: Earthquakes, Volcanoes, and the Island

[Audio] Sicily: Earthquakes, Volcanoes, and the Island. By Athena Conway..

[Audio] If you were to travel back in time, approximately 130 million years ago, between Africa and Europe, there was nothing but water. The Tethys Ocean and the Ionian Sea. Over the next few million years, water would give way to what would become one of the most studied volcanoes in the world, and the single most important land feature of Sicilian agriculture and economy. Mount Etna is "one of the most active stratovolcanoes in the world", (Geology, 2024). She is also one of the oldest, and one of the most documented. Because of her unique structure and history, scientists come to Sicily to study everything from the formation of the volcanoes in the Bove Valley depression to the magma that erupts regularly, if not on schedule. The volcano also has active lava flows, cinder cones, summit craters, and puts on beautiful displays of eruptions, all of which make it a prime research destination..

[Audio] Today, we will walk through the formation of today's Mount Etna, from 130 million years ago, through her phases, and finally to her present-day craters and cones..

[Audio] According to local guides, Mount Etna is estimated to be about 2.5 million years old, making her one of the oldest volcanoes on Earth as well as one of the most active. (Sicily, 2024). Going back 500,000 years ago, sitting in a boat, we would not see even the beginning of what would become Sicily, with Mount Etna towering over the northeastern part of the island. In the Tethys Ocean, millions of years ago, "the African tectonic plate moved [relentlessly] closer to the Euro-Asiatic plate, covering, and absorbing the Tethys Ocean" (Mulone, 2015). This is only the beginning of Mount Etna's journey. Geologists have been able to study her beginnings by travelling to the Bove Valley, which is a depression of collapsed craters. The craters collapsed in such a way that they essentially took off an entire slope of Mount Etna, showing all the layers underneath the still standing volcano. From there, scientists have been able to trace her formation from a relatively small seamount into the massive volcano she is today..

[Audio] You can split Mount Etna's formation into three phases: the pre-Etnean phase, the ancient Mount Etna phase, and the Etnean phase. In the pre-Etnean phase, approximately 700,000 and 200,000 years ago, there was just underwater volcanos called seamounts in "a large gulf in the Ionian Sea" (Etna, 2019). Over time, the seamount eventually broke the surface and began to expand. In the second phase, between 150,000 and 80,000 years ago, we would see the "formation of the present-day Mount Etna" (Szeglat, 2014)..

[Audio] In the second phase, between 150,000 and 80,000 years ago, we would see the "formation of the present-day Mount Etna" (Szeglat, 2014). In this second phase, it is a very young volcano, and eruptions were explosive. The eruptions formed two different structures. The first structure is a wide lava flow, a shield volcano spreading out. The second structure is Trifoglietto I. It is the young, conical shape of part of what will become Mount Etna in the future. A few thousand years later, Trifoglietto II was born. These two volcanoes together completely covered the seamount volcano and began to extend their slopes, and therefore the land of Sicily. About 64,000 years ago, an explosion caused the Trifoglietto craters to collapse, creating the Bove Valley depression..

[Audio] Now we travel forward in time to the third phase, approximately 25,000 years ago. We would see the "formation of many eruptive centers, one above the other, enlarging and raising continuously the Etnean structure" (Mulone, 2015)..

[Audio] The formation of Mount Etna has caused some confusion and controversy among experts. Normally, a volcano forms by compression or distension of the Earth's crust. The plates push against one another until one slips under another (subduction), or it is broken, and the two pieces move away from each other. Both of these conditions create heat and pressure, forming magma and helping it rise towards the surface. Common belief states "Etna's activity is primarily driven by the subduction of the African Plate beneath the Eurasian Plate." (Geology, 2024). However, normally, volcanoes would form right above the subducted plate, where the two plates meet. While Mount Etna sits near where the Africa and Eurasia plates meet, she does not sit above them. This has caused some experts to look for a different source of her magma. Specifically, intraplate volcanism. Parts of the oceanic African plate carry pieces of continental crust, but the continental crust does not make up the entirety of the plate. Instead of subducting completely under the Eurasian plate like an oceanic plate would, the edges collide and the "slab seems to be tearing while it sinks at a steep angle" (Wei-Haas, 2023). While the African plate sinks below the Eurasian plate, it causes "decompression melting of upper mantle material and these melts extrude at the surface in Sicily" (Monash, 2010). The magma of Mount Etna could be the result of "the 'suction' of asthenospheric material from under the…African plate" (Gvirtzman, 1999)..

[Audio] Regardless of where the magma comes from, Mount Etna has worked in tandem with Earthquakes in forming the island of Sicily. Specifically the combined earthquake and volcanic eruption of 1669. Whether the volcano caused the earthquake, or the earthquake caused the volcanic eruption, the entire eastern side of the island felt the earth rumble. Entire towns crumbled. The eruption happened along a fissure vent that split open due to the earthquake near the town of Nicolosi. Mount Etna spewed "about 9,990 million cubic yards of lava" (Britannica, 2024). After this eruption, the central crater collapsed. About 100 years later, today's central cone started to grow, and other, smaller eruptions have created the other cones on her summit..

[Audio] Today, Mount Etna is characterized by frequent eruptions from the multiple craters on her summit, often putting the surrounding natural and human habitats at risk. Despite the risks, the volcanic ash is very fertile. Lava deposits release nutrients into the soil. The island, covered in vineyards, orchards, and other crops, flourishes as the volcanic ash lava deposits have enriched the soil. The volcano has played a key role in influencing the local economy and cuisine. Tourists come from all over the world to see Mount Etna, and taste the local cuisine made from ingredients grown on her slopes..