A torrent of rock and mud erupted onto the streets of the small Swiss village of Chamoson on Tuesday, shocking residents but causing no reported casualties.
The incident, similar in appearance to a volcanic flow, was triggered by a storm that caused a riverbed to expand and burst its banks.
Screams can be heard as detritus is slung up from beneath the bridge.
The incident was filmed by Delphine Thurre, who calmly backs away from the active area whilst keeping her camera trained on the unexpected event.
As the film goes on, the height and force of the ejections seem to increase.
Bystanders can initially be seen on the other side of the bridge also apparently filming the unusual activity.
Regional radio station Rhône FM reported that some houses have been evacuated.
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