In honor of the National Park Service Centennial, join avid hikers Gary and Connie Grube for a season of guided adventures through the backcountry of Petrified Forest National Park. The Grubes have logged hundreds of miles hiking and volunteering with the park. Join them as they share their favorite gems of the Petrified Forest. The December schedule of hikes includes: * Friday, Dec. 18, 10 a.m. to 2 p.m., Onyx Bridge, a four to five-mile easy to moderate hike. Depart from the Painted Desert Inn. * Saturday, Dec. 19, 10 a.m. to 1 p.m., Historic Blue Forest (12 hikers maximum), a three to four-mile advanced hike. Depart from the Tepees; park at roadside pullout near milepost 14. This hike is for sure-footed, safety-conscious, experienced hikers wearing sturdy boots. Footing can be bad at any time, and treacherous in wet or icy conditions. Trail surface is ball-bearing gravel in some places and slippery clay in others. Walking sticks are recommended. * Sunday, Dec. 20, 10 a.m. to 1 p.m., Martha’s Butte, a three to four-mile easy to moderate hike. Depart from Dry Wash Bridge; park just south of milepost 22 on the main park road. * Sunday, Dec. 20, 1 to 3:30 p.m., Petroglyph Canyon, a two to three-mile easy to moderate hike. Depart from Rainbow Forest Museum picnic area. * Thursday, Dec. 24, 10 a.m. to 1 p.m., Historic Blue Forest (12 hikers maximum), a three to four-mile advanced hike. Depart from the Tepees; park at roadside pullout near milepost 14. This hike is for sure-footed, safety-conscious, experienced hikers wearing sturdy boots. Footing can be bad at any time and treacherous in wet or icy conditions. Trail surface is ball-bearing gravel in some places and slippery clay in others. Walking sticks are recommended. * Saturday, Dec. 26, 10 a.m. to 2 p.m., Onyx Bridge, four to five-mile easy to moderate hike. Depart from the Painted Desert Inn. * Sunday, Dec. 27, 10 a.m. to 2 p.m., Jasper Forest Road, a three to four-mile easy to moderate hike. Depart from Jasper Forest overlook parking lot. * Monday, Dec. 28, 10 a.m. to 12:30 p.m., Petroglyph Canyon, a two to three-mile easy to moderate hike. Depart from. Rainbow Forest Museum picnic area. * Wednesday, Dec. 30, 9 a.m. to 4 p.m., Red Basin Clam Beds, an eight to nine-mile moderate hike. Depart from Blue Mesa Loop Road; from the main park road, turn onto road to Blue Mesa. Drive 1.7 miles. Park at the pullout. Bring a lunch. * Thursday, Dec. 31, 10 a.m. to 1 p.m., Martha’s Butte, a three to four-mile easy to moderate hike. Depart from Dry Wash Bridge; park just south of milepost 22 on the main park road (parking is limited). The hikes are free, though regular park entrance fees apply, and are limited to 20 participants (12 for Historic Blue Forest and Sivu’Ovi). Dogs on a leash are welcome, except for Historic Blue Forest Sivu’Ovi. In case of inclement weather or extreme mud, a hike will be cancelled. Participants must wear appropriate footwear and carry water. Hats, sunblock, snacks and walking sticks are advised. If you can’t make a scheduled hike, ask at the visitor center to take an Off the Beaten Path excursion on your own. RSVPs are appreciated; call the park visitor center at (928) 524-6228, ext. 236.