In , an earthquake just prior to an eruption killed 15, people on Sicily. Despite the dangers of living near an active volcano, the eruptions made the surrounding soil very fertile, so many small villages developed on the slopes of the mountain. When Etna began to rumble and belch gas on March 8, the residents nearby ignored the warning signs of a larger eruption. Three days later, the volcano began spewing out noxious fumes in large quantities.
Approximately 3, people living on the slopes of the mountain died from asphyxiation. Even worse, Etna was soon emitting tremendous amounts of ash and molten lava. The ash was sent out with such force that significant amounts came down in the southern part of mainland Italy, in some cases nearly miles away. Lava also began pouring down the south side of the mountain heading toward the city of Catania, 18 miles to the south along the sea.
At the time, the city of Catania had about 20, residents; most failed to flee the city immediately. Instead, Diego de Pappalardo, a resident of the city, led a team of 50 men to Mount Etna, where they attempted to divert the lava flow. Wearing cowhides soaked in water, the men bravely approached the lava with long iron rods, picks and shovels. They were able to hack open a hole in the hardened lava wall that had developed on the outside of the lava flow and much of the flow began to flow west out of the new hole.
However, the residents of Paterno, a city lying southwest of Etna were monitoring these developments and quickly realized that this new flow direction could imperil their own city. They literally fought back the Catanians, while the lava breach hardened and filled again. For several weeks, the lava pushed toward Catania and the sea.
Still, the residents failed to evacuate the city. Neither was the case—the walls were quickly swallowed by the extremely hot lava and nearly 17, people in Catania died. The data have an uncertainty of about 10 feet 3 m , the INGV noted. Related: 5 colossal cones: Biggest volcanoes on Earth. In fact, the southeastern crater is now taller than its "big brother," the northeastern crater, the tallest peak on Etna for the past 40 years.
After the northeastern crater erupted in and , it reached a maximum height of 10, feet 3, m. But that height decreased over the years as the crater's edges collapsed. Simplified plate tectonics cross section showing how Mount Etna is located above a subduction zone formed where the Eurasian and African plates collide. In this subduction zone, a window has torn in the subducting slab. Etna: A view of snowcapped Mount Etna.
Mount Etna is associated with the subduction of the African plate under the Eurasian plate, which also produced Vesuvius and Campi Flegrei, but is part of a different volcanic arc the Calabrian rather than Campanian. A number of theories have been proposed to explain Etna's location and eruptive history, including rifting processes, a hot spot, and intersection of structural breaks in the crust. Scientists are still debating which best fits their data, and are using a variety of methods to build a better image of the Earth's crust below the volcano.
Ruins of a small house partially buried by volcanic debris from Mount Etna. Mount Etna consists of two edifices: an ancient shield volcano at its base, and the younger Mongibello stratovolcano, which was built on top of the shield. The basaltic shield volcano eruptions began about , years ago, while the stratovolcano began forming about 35, years ago from more trachytic lavas.
The volcano's slopes currently host several large calderas which formed when the roofs of magma chambers collapsed inward, including the east-facing, horseshoe-shaped Valle de Bove. Etna's current activity consists of continuous summit degassing, explosive Strombolian eruptions, and frequent basaltic lava flows. Ash clouds from the explosive eruptions are especially hazardous to aircraft, since ash that is pulled into a jet engine can melt, coat moving parts with a layer of glass, and cause the engine to shut down.
These dangerous ash clouds are often visible from space. Etna has also produced pyroclastic flows, ashfalls , and mudflows, but the lava flows are the most immediately hazardous type of activity, especially to the city of Catania. The lava flows themselves usually do not move fast enough to threaten humans, but they can cover large areas and destroy crops and buildings.
In the event of a large flank fissure eruption, evacuating the inhabitants of towns and cities near the volcano would be a huge challenge. Mount Etna ash plume: An oblique photograph of Mount Etna looking to the southeast taken by astronauts onboard the International Space Station on October 30, The dark plume rising from the top of the volcano is an ash cloud. The broad white cloud streaming from areas of lower elevation is smoke produced by forest fires ignited as a hot lava flow moved through a pine forest.
The ash and smoke caused air traffic to be diverted and forced the closing of roads, schools and businesses. Larger Image. This photo is looking to the southeast with the Mediterranean Sea in the background and was taken by astronauts onboard the International Space Station on October 30, The scene shows the ash plume from the eruption being carried by wind across the Mediterranean Sea to Libya, over miles away.
A Sicilian vineyard growing in the shadow of Mount Etna. The inhabitants of Sicily must balance the advantage of rich volcanic soil with the dangers of losing their crops and farms to an eruption from the still-active volcano. Etna's eruptions have been documented since BC, when phreatomagmatic eruptions drove people living in the eastern part of the island to migrate to its western end. The volcano has experienced more than eruptions since then, although most are moderately small.
0コメント