A popular canyon area of Joshua Tree National Park has been shut down because vandals have defaced the area with graffiti splashed across rocks and archeological sites, officials said Monday. 
 
 Rattlesnake Canyon has been shut down temporarily as park officials assess the damage, which apparently has been encouraged by people on social media sites, according to officials. 
 
 "The continued malicious desecration of the national park has now impacted archeological sites," park officials said in a statement. 
 
 Park rangers began noticing the scrawls in January. "While this started as a few markings," officials said, "the use of social media has appeared to spark numerous individuals' interest in adding to the vandalism." 
 
 The area will be closed at least through April 30. After that, officials will consider reopening the area. 
 
 ALSO: 
 
 
 
 Jenna Jameson's court date set in Newport Beach battery 
 
 Nancy Reagan says Thatcher was husband's 'political soul mate' 
 
 Autopsy: Rick Warren's son died of self-inflicted gunshot wound 
 
 
 
 Twitter: @LAJourno 
 
 robert.lopez@latimes.com ||||| Zuma Press More than 300 acres of Joshua Tree National Park, top, have been closed. 
 
 For years, millions of visitors drawn to the peculiar beauty of Joshua Tree National Park have stayed on the straight and narrow while hiking the steep and twisty trails: picking up their trash and heeding authorities' pleas to leave the park's granite monoliths and blooming desert floor unmolested. 
 
 But in recent months the park has been hit with an unusual scourge of graffiti. This week, the escalating problem prompted park rangers to close a large area of the attraction because of widespread graffiti found in a popular canyon. That came on the heels of the closure of another part of the park after it also had been defaced. More than 300 acres are shut to visitors while officials investigate. 
 
 "People are appalled and people are wondering how it could happen here, in a national park," said Pat Pilcher, a ranger at Joshua Tree. 
 
 Enlarge Image Close National Park Service The closure came amid an investigation of graffiti. 
 
 Most of the park, which sits 140 miles east of Los Angeles at the crossroads of the Mojave and Colorado deserts, is still open. But the closures come at the height of the park's busy season, and affect one of its most popular areas, Rattlesnake Canyon, which is rugged and remote, with large rock formations and water pools fed from a natural spring. The park attracts about 1.3 million visitors a year. 
 
 The closure also highlights the struggle of park rangers to welcome more visitors while minimizing their impact on delicate ecosystems and historic sites. 
 
 Earlier this year, graffiti carvings discovered at another of the park's historic locations, the Barker Dam, prompted officials to close it to visitors. The trail around the 100-year-old dam is still open, but an area around the dam itself is closed indefinitely, park officials said. Rattlesnake Canyon is scheduled to remain closed for the rest of the month. 
 
 The sites are closed while investigators try to track the vandals and assess and repair the damage, park officials said. In pictures released by the National Park Service, the words "oatmeal cookie" and "nature boy" appear to be painted or spray-painted on boulders in Rattlesnake Canyon. 
 
 Investigators with the National Park Service, which administers the park, believe that posts on social media played a role by sparking "numerous individuals' interest in adding to the vandalism," a National Park Service statement said. 
 
 Park officials declined to comment further on the investigation, or reveal which social-media outlets were used. Defacing National Park property carries a maximum sentence of 6 months in prison and a $5,000 fine, they said. 
 
 Some of the graffiti may have damaged ancient, Native American petroglyphs, Mr. Pilcher, the park ranger, said. Humans are believed to have settled in the area 5,000 years ago. The damaged rock art might be remnants of early settlements of the Serrano or Chemehuevi Indian tribes, Mr. Pilcher said. 
 
 Park officials said they are still determining how to remove the graffiti without doing more damage. It is also unclear how much those efforts might cost, they said. 
 
 Vandalism in the country's 401 national parks is rare, National Park Service officials said, but it still occurs. In 2003, the service saw 7.3 incidents of vandalism per park—which includes graffiti or any other kind of damage—according to federal records. That dropped to 4.8 incidents in 2012. 
 
 Some places have seen problems persist. Officials at the Glen Canyon National Recreation Area in Arizona started a Graffiti Removal and Intervention Team, and this year are recruiting volunteers to scrub off graffiti with water and wire brushes, according to the Glen Canyon website. 
 
 In the 2012 fiscal year, 287 million people visited national parks, according to federal records. 
 
 Jeffrey Olson, a spokesman for the National Park Service, said that normally, if a visitor drops so much as a candy wrapper, he will pick it up immediately or be prodded by others to do so. 
 
 "People are protective of their parks," he said. "It makes it all the more shocking that somebody would defile our heritage." 
 
 Write to Tamara Audi at tammy.audi@wsj.com
– Some 300 acres of California's Joshua Tree National Park are closed to visitors thanks to a rare spate of graffiti. First, park rangers closed an area surrounding a historic dam following the discovery of carved graffiti. Then, this week, the popular Rattlesnake Canyon was closed after words—including "nature boy" and "oatmeal cookie"—were found painted onto boulders, the Wall Street Journal reports. The canyon is set to be closed for the rest of the month, while the dam area is closed indefinitely, officials say. "People are appalled and people are wondering how it could happen here, in a national park," says a ranger. Indeed, just 4.8 incidents of vandalism per park occurred last year. One possible reason for the graffiti's spread: social media, which "has appeared to spark numerous individuals' interest in adding to the vandalism," rangers say, per the Los Angeles Times. (The Post notes they didn't specify which social media sites may be involved.) It's not just natural beauty at risk: "The continued malicious desecration of the national park has now impacted archeological sites," officials say. Native American petroglyphs may have been damaged; rangers are trying to figure out how to clean the sites without hurting them further.