Something strange is happening deep in the Stanislaus National Forest — an underground fire that dates at least to 2014.
It is burning in a small area near Rosasco Meadow, about 12 miles southwest of Twain Harte and seven miles west of Yosemite National Park.
How the fire started, and what’s fueling it, are a mystery, Groveland District Ranger Jim Junette said by phone Friday. He oversees the southern part of the Stanislaus.
The fire has consumed tree roots in a rough circle with about a 200-foot radius, but it’s too risky to get a close look, Junette said.
The site is amid the 150,000-plus acres burned in the Rim Fire of 2013. Junette said fires have been known to flare up after a year, but not this long. He checked lightning records and found nothing that would explain the ignition.
The site is close to the route of a railroad that hauled logs out of the woods until the 1960s. Junette said it’s possible that the remains of creosote-treated ties might play a part in today’s fire.
“The only thing we compare it to is some coal-seam fires in the Midwest that have been burning for decades,” he said.
The flames have flared up into above-ground fuels at least twice since 2014, he said. That prompted the forest staff to launch an effort this month to reduce the woody fuel on about 700 acres in the vicinity. Much of this is being done with intentional burning of fuel near the ground to prevent an out-of-control blaze.
The mild wildfire season so far has allowed this and other fuel-reduction projects to make progress, Stanislaus spokeswoman Diana Fredlund said.
The work near the underground fire started Tuesday, Sept. 3, and is expected to last 10 days. The road and trail that reach that area are closed to the public.