How lightning ignited the Marion Fire on a blue-sky day
It was a hot and sunny day in the Mount Jefferson Wilderness last Saturday, with nary a cloud in the sky, when a plume of smoke appeared above Marion Lake's southwest shoreline just before noon.
Visitors that were swimming when the fire broke out saw trees flame up like matchsticks, before beating a hasty retreat three miles back to the Marion Lake Trailhead east of Detroit.
"Fire crews entering the forest met us on the trail as we departed," said Kathy Moran, who was visiting Marion Lake with her family that day.
The Marion Fire would eventually grow to 120 acres, require over 100 firefighters and shut down most trails in the popular recreation area.
The fire is 90 percent contained now, and crews are doing mop-up work, but how the fire started remains an interesting question. It offers a window into how dry Oregon's forests are during this drought-stricken season and the destructive power of one tiny smoldering spark.
The official cause of fire was a lightning strike. But it wasn't a strike that happened that sunny Saturday, the day before or even the week previous. The lightning strike blamed for the Marion Fire actually hit 10 days earlier, during a storm on July 8.
"It's often a surprise to the public, because while there's a heightened sense of awareness at the time of lightning storm, once you get past a week, it recedes from memory," said Chris Donaldson, assistant fire management officer with Willamette National Forest. "But it's not uncommon for fires to pop up a week or sometimes more after the storm."
Donaldson said that when lightning storms come through with rain, some fires pop up immediately while other smolder in what are known as strike trees — trees hit by lightning.
As the forest dries from the storm, the smoldering spark can remain for weeks and even months before the tree falls down, or a gust of wind sweeps it into the forest to catch fire.
That appears to be what happened with the Marion Fire. Firefighters said they found a strike tree that correlated with a lightning strike mapped during the July 8 storm.
"Any firefighter can identify a strike tree," Donaldson said. "There's a very specific impact, this gash that spirals up the tree, that's pretty specific. Plus, there's usually 'tree shrapnel' all around, these two-foot toothpicks from the explosion."
The smoldering spark can remain in a strike tree for a remarkably long time.
In 2012 near Mount Fuji, on the south end of Willamette National Forest, a strike tree was found smoldering two months after the original lightning storm. It never became a large fire, but it easily could have in conditions as dry as this season.
One lesson from these incidents, Donaldson said, is how destructive one spark can be. It's the reason campfires are currently prohibited everywhere in Willamette National Forest except developed campgrounds.
He said that recently in the Opal Creek Scenic Recreation Area, a campfire that hadn't been completely put out came close to exploding into a full-blown wildfire.
"Right now we have the right conditions for even a small spark to pick up and get large quick," Donaldson said.
Trails remain closed
Even with the fire winding down, there is no timetable for reopening the trails in and around Marion Lake.
"It's going to depend on how firefighting efforts go this week," said Joan Schmidgall, public information officer for Willamette National Forest. "Next week we'll reevaluate."
Schmidgall said safety would be the priority, considering the number of hazardous snags and loose rocks caused this fire and past fires in the same area.
Zach Urness has been an outdoors writer, photographer and videographer in Oregon for seven years. He is the author of the book "Hiking Southern Oregon" and can be reached at zurness@StatesmanJournal.com or (503) 399-6801. Find him on Facebook at Zach's Oregon Outdoors or @ZachsORoutdoors on Twitter.