<p dir="ltr">Los Angeles County firefighters hike on a fire line near Groveland, California, as smoke rises from the massive <a href="http://news.nationalgeographic.com/news/2013/08/130826-california-yosemite-national-park-rim-fire-wildfires-history-science/">Rim Fire burning near Yosemite National Park</a>.</p><p>Now into its tenth day, the Rim Fire threatens 4,500 homes outside of Yosemite National Park. Fire crews have contained about 20 percent of the wildfire, which has burned some 160,000 acres—an area about the size of Chicago.</p><p><strong></strong></p><p dir="ltr">"There have been bigger portions of Yosemite burned in other fires, but there's never been a fire as big as this one in Yosemite if you take the [Rim Fire] as a whole," explained Tom Medema, a spokesman with Yosemite National Park.</p><p><strong></strong></p><p dir="ltr">To battle the massive blaze, 62 fire crews, consisting of more than 3,600 firefighters, have been called to the scene, Medema said in an interview on Monday.</p><p><strong></strong></p><p dir="ltr">The firefighters are assisted by 16 helicopters, 454 fire engines, 39 water tenders—wheeled water tankers—and a handful of other aircraft, Medema added.</p><p dir="ltr">—Ker Than</p>