Mount Vesuvius, in what is today western Italy, erupted violently in 79 CE. Residents of the nearby towns of Pompeii and Herculaneum were devastated by a rain of pumice more than 2 meters (6 feet) deep, followed by flows of scorching, toxic gases.

Illustration by Peter V. Bianchi, National Geographic

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  • On August 24, 79 CE, Mount Vesuvius erupted. Mount Vesuvius is a volcano in what is today western Italy. The Roman resort towns of Pompeii and Herculaneum were devastated by the two-day event, one of the most famous and deadly in European history.
    The eruption occurred in two phases. In the first phase, Mount Vesuvius spewed a giant column of volcanic gas, volcanic ash, and rock high into the atmosphere. A type of rock called pumice rained down on towns surrounding the volcano. The harsh rain of pumice injured people who were outdoors and clogged roads, doorways, and drains. The rocks built up to a height of about 2.5 meters (8.2 feet). The build-up became so heavy that it collapsed roofs on homes and businesses, crushing or trapping people inside. This phase, called a Plinian eruption, lasted nearly a day.
    The second phase was even more destructive. This phase was characterized by pyroclastic flows. A pyroclastic flow is a very fast-moving current of volcanic gas and ash rushing down the side of a volcano. Some of the gases flooding Pompeii and Herculaneum were toxic, and may have included hydrogen sulfide and carbon monoxide. Many residents of Pompeii who were unable to evacuate during the first phase of the eruption suffocated during the second phase. Even more victims burned to death, as the gases reached temperatures of up to 300 degrees Celsius (570 degrees Fahrenheit), “enough to kill hundreds of people in a fraction of a second,” according to one volcanologist.
    Mount Vesuvius is still an active volcano. In fact, it is considered one of the most dangerous volcanoes in the world. Its last major eruption was in 1944.
  • Term Part of Speech Definition Encyclopedic Entry
    active volcano Noun

    volcano that has had a recorded eruption since the last glacial period, about 10,000 years ago.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    characterize Verb

    to describe the characteristics of something.

    collapse Verb

    to fall apart completely.

    column Noun

    strong, vertical support structure, such as a pillar.

    current Noun

    steady, predictable flow of fluid within a larger body of that fluid.

    Encyclopedic Entry: current
    destructive Adjective


    devastate Verb

    to destroy.

    erupt Verb

    to explode or suddenly eject material.

    evacuate Verb

    to leave or remove from a dangerous place.

    fraction Noun

    number expressed as a ration, such as a/b.

    phase Noun

    stage in a process or transformation.

    Plinian eruption Noun

    powerful, violent volcanic explosion characterized by pyroclastic flows and ejection of material high into the atmosphere.

    pumice Noun

    type of igneous rock with many pores.

    pyroclastic flow Noun

    current of volcanic ash, lava, and gas that flows from a volcano.

    Encyclopedic Entry: pyroclastic flow
    resort Noun

    facility or space people go to relax in a luxury setting.

    rock Noun

    natural substance composed of solid mineral matter.

    spew Verb

    to eject or discharge violently.

    suffocate Verb

    to be unable to breathe.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    toxic Adjective


    volcanic ash Noun

    fragments of lava less than 2 millimeters across.

    Encyclopedic Entry: volcanic ash
    volcanic gas Noun

    gas such as water vapor or carbon dioxide that is released into the atmosphere by a volcano.

    volcano Noun

    an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

    Encyclopedic Entry: volcano
    volcanologist Noun

    scientist who studies volcanoes.