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As the name suggests, a shield volcano is broad and flat, like a shield. Made primarily of lava flows, shield volcanoes are less dangerous than the smaller stratovolcanoes. Examples include the Hawaiian islands, the base of Mount Etna (upon which several stratovolcanoes were built), Geldingadalir in Iceland, and Erta Ale in Ethiopia. Their lavas are generally fluid and runny, allowing them to spread farther from a vent than a stratovolcanoâs lava would. As they travel farther from their source they eventually cool, forming a new layer to the shield volcano. Their slopes are weak, and thus prone to fissure eruptions, which send curtains of fire hundreds of feet into the air.
Kilauea is a shield volcano in the United States. Its broad surface features a long series of craters (aptly named the Chain of Craters) on its East Rift Zone, extending from the summit to the eastern tip of the Big Island. In May of 2018, a series of fissures emerged in the Leilani Estates, wiping out dozens of homes and creating massive lava flows.
Also known as a composite volcano, a stratovolcano is a mountain made of layers, or strata, of pyroclastic material and lava flows. Widely considered to be the most dangerous type of volcano, theyâre common along subduction zones in the earthâs crust, where plumes of molten rock rise into the magma chamber, eventually leading to an eruption.
One one side of the eruptive spectrum (otherwise known as the Volcanic Explosivity Index, or VEI) are Strombolian eruptions. Named after the Italian stratovolcano Stromboli, these gas-driven explosions propel small lava fountains into the air, lasting only a few seconds each.
On the opposite side of the VEI are Plinian eruptions. These eruptions are large and violent, unleashing pyroclastic flows, ash columns, lava bombs, pumice, and tephra upon anyone unlucky enough to be caught in one. On October 24, AD 79, Mount Vesuvius erupted with such force that the entire volcanic cone was destroyed by the next day. Vesuvius ejected an ash column several miles into the atmosphere, which was so heavy that it later collapsed on itself. Pyroclastic surges razed the towns of Pompeii, Herculaneum, and Stabiae to the ground.
A witness of the eruption, Pliny the Younger, was responsible for the first and most detailed account of a volcanic eruption in recorded history. It seemed prudent that the type of eruption he described at Vesuvius should be named after him.
Another famous stratovolcano is Mount Etna, on the island of Sicily. Not only is it one of the most active volcanoes on earth, but it was also featured in the Mustafar scene of Star Wars: Revenge of the Sith.