The Detwiler fire began near Lake McClure and has been feasting on dry grass and brush since then. An exceptionally wet winter followed by a very hot and dry summer has given the fire plenty to snack on.
"I can't emphasize enough how active and erratic this fire activity is," Mariposa County Sheriff Doug Binnewies said in a statement. "It's done stuff that we haven't seen before."
The small city of Mariposa has been completely evacuated along with numerous other communities, totaling over 4,000 Californians displaced. Governor Jerry Brown has declared a state of emergency in Mariposa County.
The fire almost doubled in size from 39 to 70 square miles in area between Tuesday night and Wednesday morning, according to the California Department of Forestry and Fire Protection (Cal Fire).
Detwiler fire!— Robert D Barnett (@Firefighterdale) July 19, 2017
Be safe! pic.twitter.com/8eTAUIXAVY
"The communities of Hunters Valley, Bear Valley, and Hornitos continue to be threatened as the fire encroaches on culturally and historically sensitive areas," Cal Fire said. In addition, the flames are licking power lines that service Yosemite National Park, the most famous nature preserve in the United States. The fire is still 35 miles away from the Park, which remains open.
More than 2,200 firefighters have trudged deep into the county's forests to try to extinguish the flames, but they are steadily being pushed back and closer to human settlements. Nine tanker planes and 11 helicopters have taken the battle against the fire to the skies.
"Any time you have a fire like this and you have a community like this, it's going to be considered threatened," said Cal Fire spokesman Isaac Sanchez in a statement. "When you add the fact that there are foothills, when you add in the slopes and the grades and the temperatures we are dealing with, the humidities we are dealing with, it's a full-on challenge."
"It is the fuels that are extremely flammable right now due to heavy rains this winter with widespread growth and then extended heat waves this summer, which has created a powder keg for fast-burning fuels," wrote the National Weather Service in a statement. "Even terrain-driven winds can become stronger depending on fire behavior and fuels.
The "extreme and aggressive fire behavior" has been frustrating the attempts of firemen to contain it as favorable winds allow the fire to spread faster than it can be suppressed. Only seven percent of the fire has been contained, and at least eight structures have been destroyed by it. Another 1,500 structures are threatened by the fire.