(09-09) 19:25 PDT MOUNT DIABLO -- A wildfire that raced over the bone-dry summit of Mount Diablo threatened 100 homes near Clayton on Monday and led some cities to cancel recreational sports because of smoke, but favorable winds gave firefighters hope they could isolate the inferno in unpopulated canyons.
Though the Morgan Fire, which broke out Sunday afternoon, tripled in size and had scorched more than 3,700 acres of dry brush and old oaks, crews operating from land and air - with bulldozers, planes and helicopters - managed to steer the flames mainly into steep canyons southwest of the summit.
The historic visitor center and lookout on Mount Diablo was saved - at least for now.
Flames and thick plumes of smoke rising from the top of the 3,848-foot mountain gave the East Bay's tallest peak the look of a volcano, forcing the evacuation of animals and livestock below, and prompting air pollution advisories in three neighboring counties. Danville and Pleasanton, among other cities, called off some outdoor events for youth and adults.
At lower reaches, crews bulldozed containment lines in an effort to protect roads and ranches. Overhead,Wholesale Pittsburgh Steelers Jersey, three helicopters and as many as six airplanes dropped water and retardant on hot spots. Winds pushed the fire "back on itself" for most of the day, officials said, allowing firefighters to push containment to 20 percent.
Yet officials cautioned that the conflagration - with acres of dry foliage within reach and days of high temperatures ahead - was still active and capable of consuming more land.
"We don't have the fire established at solid control lines yet," said , a spokesman for the of Forestry and Fire Protection. "The size (of the fire) is going to increase for a while."
The good news was that the blaze was burning mostly in remote wilderness areas of Mount Diablo State Park, where structural damage was limited to a small outbuilding. No homes were lost, and just one injury - a firefighter with a hurt foot - was reported. The cause of the fire remained unknown.
An army of firefightersMore than 700 firefighters were working to keep the blaze within the park, the heart of the battle being in isolated ravines near the summit where crews were trying to stop the fire from spreading.
"There's a lot of fuel here: manzanita, oak - very thick,Neighbor says couple fought often before murder, very thick," said state firefighter as he watched flames leap as high as 40 feet in the air Monday afternoon from the side of a canyon high in the park.
A bulldozer had just cut a fire break sweeping south from Summit Road, and Griffin and the rest of his crew were fighting with hoses, shovels and axes to keep the surging blaze from crossing either the break or the road.
A gust of wind whipped the flames high over their heads, and the heat was so intense the crew backed up.
"We hope we can keep it in that canyon right there, and not let it cross the road ... we'll see," Griffin said, wiping his ash-smudged face. "This wind is pretty stiff."
She's seen it beforeLeda Tully, who lives in park housing about a half mile down from where the fire raged, was worriedly hosing down her property in preparation for flames. It's the third year in row, she said, that a wildfire has approached her house. This one had her on edge.
"You never know where these fires are going to go," she said as she blasted her side-yard fence with water. "I'm making sure. Last year's fire was a little scarier than the first, but this one is very scary."
As she spoke, an aircraft dropping retardant flew overhead.
Evacuation advisories had been issued for about 100 homes east of Mount Diablo State Park, along Curry Canyon Road and in the Oak Hill Lane area. About a dozen people stopped by an evacuation center at the , though most made arrangements to stay elsewhere.
Getting the animals outHorses and other livestock have also been evacuated from the area, which is made up largely of sprawling ranches and rural houses.
Fourteen horses, including eight miniature horses, were evacuated to the Equestrian Center of Walnut Creek, a shady array of arenas and paddocks near Heather Farm Park.
"It was an easy decision. Of course we were going to open our facility," said , who sits on the board of the nonprofit center. "We'll stay here 24 hours a day as long as that fire is burning."
was among those who brought horses. A fifth-generation Concord resident, she said she had seen Mount Diablo burn before and knew not to take chances. When she saw smoke Sunday afternoon, she raced to her Morgan Territory Road property with her horse trailer to rescue her Palomino, Trigger, and her red roan, Banner.
"We got there and the horses were freaking out - racing around, whinnying, bucking," she said. "The ash was coming down, the helicopters were on top of us, and the flames were just across the road."
Coyotes and rabbits were spotted fleeing the fire for safer brush, and bands of tarantulas crossed park roads to escape the heat.
, who grew up in Clayton and now lives in Concord but works at the , said he had seen fires in the area before, but added, "This is the biggest wildfire we've had since I've lived here."
Fire officials advised his parents to leave their Morgan Territory Road property, but they chose to stay because the fire still seemed a safe distance away.
Brush becomes fuelThe last major fire on Mount Diablo was in August 1977, when a lightning strike ignited vegetation and sent flames across 6,000 acres. Little prescribed burning has been done since then to reduce the amount of flammable fuel on the mountain, Shew said.
"When brush has that much time to build up," he said, "that of course just provides more fuel."
Firefighters succeeded early Monday in saving the Mount Diablo lookout, a visitor center called the that dates to the 1930s. The blaze burned within 50 feet,Ben Roethlisberger Jersey, but firefighters kept the flames from advancing on the sandstone building.
"The building seems to be OK for now, but the fire could still take a turn and climb back up," said , a spokesman for the Moraga Orinda Fire District.
The Bay Area issued a smoke advisory Monday, recommending that residents in parts of Contra Costa,Wholesale Pittsburgh Steelers Hats, Alameda and Santa Clara counties - particularly the elderly, children and those with respiratory problems - limit or avoid exposure.
Kevin Fagan, Carolyn Jones and Kurtis Alexander are San Francisco Chronicle staff writers. E-mail: , , Twitter: