A stormy afternoon in Germany turned into a rare seismic experiment.
A seismometer in Bensberg, Germany, recorded a lightning strike that hit a nearby tree, the following thunderclap, and then the tree's explosion.
The tree exploded most likely due to the energy of the lightning strike heating the water and sap in the trunk and turning it into steam.
A fourth spike in the seismic signal corresponds to the air pressure from the tree explosion hitting the lab.
As dark clouds rolled in from the west on a July afternoon last year, Klaus-G. Hinzen, a seismologist at the University of Cologne in Germany, knew a big storm was brewing. He was watching from the window of the university's earthquake observatory in Bensberg, a small town outside of Cologne, as lightning struck a nearby hotel. Less than a minute later, a flash took out a tree next to the earthquake lab itself, turning that stormy afternoon into a rare seismic experiment.
"The main experience that we seismologists have with lightning strikes is a very bad one, because it often causes a lot of damage in the equipment. But the equipment didn't fail this time," Hinzen told OurAmazingPlanet. "It's a rare instance that you have a lightning strike so close to so many different seismometers and get a complete record of it."