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. … Chemical engineering and materials science Professor 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."