Fortuitous Fire Exposed Previously Unknown Archaeological Sites

UTAH DIVISION OF FORESTRY OFFICIALS announced earlier this week that an 800-acre brush fire in Emery County on July 18 – 22 was caused by a freak act of nature.  The area is rich in pre-historic Indian sites and the fire was spotted by a University of Utah archaeological expedition that was just leaving the area after a 10-day dig.

The Deseret News reported Monday:

(The fire) began July 18 when a boulder fell 800 feet from a cliff face, bounced several times, collided with a larger boulder and came to "an instantaneous stop," said Jason Curry, spokesman for the Utah Division of Forestry, Fire and State Lands.

"It's kind of a rare one," Curry said Monday, describing the conclusion investigators reached after looking at physical evidence found at the fire's point of origin and interviewing people who were in the area when the blaze began.

The falling boulder was the size of a refrigerator, Curry said. The boulder it collided with was the size of a sport-utility vehicle. The heat generated by the "pressure friction" that occurred when the two boulders came together ignited the surrounding grass and brush, according to Curry. "It's like hitting an anvil with a hammer," he said. "It doesn't cause a spark, but it still generates heat."

There were no campfires burning in the area when the fire started, and lightning was ruled out as a factor as well. "That left rock fall as the only cause," he said.

Broken sandstone-quartzite boulder gives testament
to thepoint of origin of the "Lighthouse Fire"
(Utah Division of Forestry photo)

The Salt Lake Tribune explains further:

Curry and three investigators tried to make sense of what they found at the origin of the fire. There was green grass at the bottom of a sheer drop-off and freshly disturbed dirt.  "We found some pretty violent rockfall in the area," Curry said.

Witness accounts said there were no people in the area of the fire when it started, there was no lightning that day.  "We were pretty puzzled," said Curry, who added that he was "very hesitant" to assign the cause of the fire as rockfall, mostly because he had never heard of it.

Curry said that in talking with geologists and physicists they determined, although it is very rare, that it was plausible for a fire to start from the two boulders — composed of sandstone and a little bit of quartzite — hitting each other.

The sandstone boulder fell 200 feet and then bounced 10-12 times downhill, making another 600-foot descent before coming to an abrupt halt.  "Just the sheer amount of energy trapped in that boulder … it all came to a stop instantly," Curry said.

While the cause given is extremely rare, there have been at least 8 other wildfires over the past half-century known to have started from rockfall.

The fire that was dubbed "the Lighthouse Fire" by Forestry, had a positive consequence however.  The overal area known as the Range Creek archaeological site has about 400 known pre-historic sites and the brush fire uncovered several more that were previously unknown.  The Deseret News continued:

The fire, which was contained July 22, exposed a number of previously undiscovered sites in the canyon, according to Shannon Boomgarden, assistant director of the Range Creek Field School.

"We got right back in there and started surveying, and we were able to record 12 new sites," she said, noting that most of the new discoveries were historic in nature, rather than prehistoric. "We found a road that we didn't know was there because it had been covered by sage brush," Boomgarden said.

Neither the fire nor the efforts to extinguish it damaged any of the known archaeological sites in the canyon, she said.

Read the full article in the Deseret News HERE.
Salt Lake Tribune story HERE.

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