A fire that burned more than 20 acres near an Orange County golf course was started by sparks from a golfer's club striking a rock, and it's not the first time a rough lie turned into a fire hazard.
Investigators confirmed the cause of the fire after speaking with witnesses who were at Arroyo Trabuco Golf Club Tuesday afternoon in Mission Viejo.
"The golfer had hit the ball into the rough," Orange County Fire Authority Capt. Larry Kurtz told the Orange County Register. "As he was trying to get it out he accidentally hit a rock and it started a fire."
The golfer tried to put out the fire, but flames spread quickly in dry brush. The fire threatened nearby homes, but no structures were damaged and no injuries were reported.
The fire was knocked down about two hours later.
A 2014 UC Irvine study determined that titanium alloy clubs caused sparks that generated a small brush fire at Irvine's Shady Canyon in 2010 and another a few years earlier at Arroyo Trabuco.
The UC Irvine study was in collaboration with the Orange County Fire Authority. The university's engineering department collected rock and plant samples, then repeatedly struck the rocks with a titanium coated golf club in a laboratory.
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"Rocks are often embedded in the ground in these rough areas of dry foliage," chemical engineering and materials science Prof. James Earthman, lead author on the study, said. "When the club strikes a ball, nearby rocks can tear particles of titanium from the sole of the head. Bits of the particle surfaces will react violently with oxygen or nitrogen in the air, and a tremendous amount of heat is produced. The foliage ignites in flames."
Researchers said they did not see sparks when using a more common steel head club.
The study noted the lightweight metal can generate heat of more than 3,000 degrees -- creating a dangerous combination with California's drought. The state is in its fifth straight year of drought.