Researchers detonate ping pong balls to better understand eruptions

Tracking how far volcanic debris flies during an eruption, even a small, simulated blast filmed by powerful cameras, is not easy.

It appears, though, that an international research team led by UB volcanologist Greg Valentine has found a way—but only after visiting a sporting goods store.

“I got a laugh from the guy at Dick’s when I walked in to buy 150 ping pong balls,” says Alison Graettinger, a postdoctoral associate at UB who helped facilitate the 12 simulated eruptions last month in Ashford, roughly 50 miles south of Buffalo. The team also used tennis balls to trace where the mock debris travelled after each blast.

The experiments were designed to increase our understanding of what happens during volcanic eruptions, one of Earth’s most powerful and mysterious natural occurrences. Researchers are still analyzing the results, but Valentine, professor of geology and director of UB’s Center of Geohazards Studies, says the tests are a rarity for a field that relies heavily on computer modeling.

He expects them to produce a first-of-its-kind dataset that will yield results that garner worldwide attention and, ultimately, yield data that will help safety officials better prepare for and respond to volcanic eruptions.

Working on land owned by Cheektowaga-based Calspan Corp., the research team, which consisted of 17 scientists and nine students from five countries, dug two trenches—one 30 inches deep, the other 45 inches deep. They filled the trenches with different layers of gravel and sand to measure how deep the blast’s impacts would be.

On test day, researchers hammered into the trench creating 12 small holes 18 inches deep. They placed an explosive about as powerful as a firecracker into each hole and covered the hole with more gravel.

The researchers then set ping pong balls and tennis balls on the surface above the explosives. Graettinger previously had injected mixed limestone sand into the ping pong balls to create three weight classes distinguished by white, orange and red markings. The 42 tennis balls were of uniform weight.

Researchers then detonated the explosives, which buried some ping pong balls in the impact crater and sent others as far as 100 feet into the woods. In addition to measuring where the ping pong balls and tennis balls travelled, they monitored each blast with high-speed cameras, infrasound microphones, seismometers and other high tech equipment.

The researchers collected the same type of information they would during an actual volcanic eruption. The idea, Valentine explains, is to use the data to determine the energy of each blast.

Controlled experiments like those at Ashford can provide clues into what causes volcanoes to act the way they do. For example, many volcanoes erupt repeatedly from the same crater, yet few experiments have been done to examine how the pre-existing craters affect the later eruptions.