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Most people know the story of Pompeii and how Mount Vesuvius erupted, burying the ancient Roman town. But what is not well known is that a witness of the eruption was the great Roman naturalist Pliny the Elder (above) who, as commander of a fleet stationed nearby, launched a rescue operation. Despite his efforts, thousands died. But the manner of their death preserved them and their city for posterity. A new exhibition on Pompeii opens this week at the Australian National Maritime Museum.
VOLCANOES A volcano is a point on the Earth's crust where magma, a form of molten rock from the mantle (the layer beneath Earth's crust), is able to push through.
They occur in parts of the world where two or more tectonic plates (hard pieces of Earth's crust sliding around on the upper layer of the mantle) meet.
At these tectonic boundaries the plates either spread apart (spreading or divergent boundaries), slide under the other (subduction or convergent boundaries), or rub up against each other (transform boundaries).
At divergent and convergent boundaries, the plates are relatively thin and fissures form allowing magma to escape from the mantle. On its way to the surface the magma collects rocks, gases and other chemicals that may change its composition. Once it bursts through the crust it becomes lava.
The material thrown out of this hole often builds up into a cone-shaped hill or mountain, thereby creating the volcano.
While some volcanoes remain active for centuries ejecting lava, rock, smoke, gas, ash and other material, others become inactive over time.
VESUVIUS Mount Vesuvius is a stratovolcano, meaning it was built from lots of layers of different material including lava, volcanic ash and other material hurled up by the volcano's violent eruptions.
Vesuvius is one of a group of volcanoes in southern Italy known as the Campanian volcanic arc, where the European and African tectonic plates meet. Vesuvius is thought to have formed about 200,000 years ago. It had been dormant since the 8th century BC before it erupted in AD79.
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