Science Scoops: What's in Vesuvius' Belly?
by Stephen James O'Meara
Lava! And lots of it! That's right. According to a team of European researchers, a giant pool of magma (what lava is called when it is underground) lies beneath Mt. Vesuvius, the volcano that buried the Roman cities of Pompeii and Herculaneum in a.d. 79. The molten reservoir is at least 390 square kilometers in size and lies 8 km below the surface, under some of the most scenic coastline in Italy. It stretches from the nearby Apennine Mountains to the Phlegraean Fields—the series of volcanic structures upon which the city of Naples is built. “It was really unexpected for the reservoir to be that size—so very wide and large,” says Paolo Gasparini (University of Naples), the lead researcher.
The scientists determined the size of the molten pool by setting off a series of explosions in the earth and then monitoring the seismic signals—a technique called seismic tomography. The echoes they got back from their explosions were used to build a three-dimensional picture—sort of like the way sonar (underwater sound wave technology) is used to map the topography of the ocean floors. The researchers hope to watch for seismic clues that should provide a tip-off before the next eruption, which could happen at any time.
Meanwhile, Italian archaeologists have also discovered one of the world's best-preserved prehistoric villages, a “Bronze Age Pompeii” buried in volcanic ash near that Roman city. The ancient settlement was overwhelmed by volcanic debris when Mount Vesuvius erupted around 1800 b.c., smothering the village near present-day Nola in southern Italy many centuries before Pompeii suffered the same fate.
- seismic: Of, subject to, or caused by an earthquake or earth vibration.
- topography: Graphic representation of the surface features of a place or region on a map, indicating their relative positions and elevations.
- One of the reasons that scientists study volcanoes is to gather information to help them predict when a volcano might erupt. What other reasons might scientists have for studying volcanoes? What might scientists be able to learn about the different layers of the Earth and the Earth's plates?
[anno: Answers will vary but could include that scientists can learn about the different kinds of gases and rock that are present in the Earth's mantle. Scientists can also learn more about the movement of different tectonic plates by studying some volcanic eruptions.]
- Mt. Vesuvius is a composite volcano. Mauna Loa is a shield volcano How are these two volcanoes different?
[anno: Since Mt. Vesuvius is a composite volcano, it has steep sides that are composed of rock fragments that erupted from the volcano. Since Mauna Loa is a shield volcano, it is wider than Mt. Vesuvius because the lava that erupted from the volcano poured out slowly.]