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.
- What were scientists surprised to discover about the pool of magma beneath Mt. Vesuvius?
[anno: Scientists were surprised to discover that the pool of magma is much larger and wider than they originally believed it to be.]
- The article states that scientists have used seismic tomography to map the magma pool. What might this kind of a map or image look like? What kind of shape might the magma pool have? Draw a diagram showing a cutaway of Earth's surface where the pool of magma lies. Show what the land looks like above the area of the magma pool. How wide is the pool of magma under Earth's surface? How far below the surface is the magma pool? Where does the magma pool vent to Earth's surface? Include a scale for size on your diagram. You may wish to look at a topographical map of the area around Mt. Vesuvius to help you with your diagram.
[anno: Diagrams will vary but should show a pool of magma that extends under a diagram of Mt. Vesuvius and the surrounding areas of the Apennine Mountains and the Phlegraean Fields. Students' diagrams should be drawn to scale approximating a pool that is 8 km beneath the surface of Earth.]
- Study the diagram that you have made. Imagine that heat-energy were being captured from this magma. What might be some of the benefits of using this pool of magma as a heat energy source? What might be some of the drawbacks of using this pool as a heat-energy source? Write a few sentences for your answer.
[anno: Answers will vary. Students may think that a benefit to using the magma pool as an energy source would be that collecting heat energy from the magma would not involve depleting Earth of fossil fuel resources. A drawback to using this pool as a heat energy source might be its distance beneath Earth's crust and the difficulty in getting to the magma.]