http://www.huffingtonpost.com/2013/10/18/goblin-valley-boy-scout-leaders-destroy-rock_n_4122488.html
The "goblin" the group knocked over, also known as a "hoodoo," forms when a harder rock sits atop softer rock. Over millions of years, the harder rock on top protects the softer stone directly beneath it. The soft matter elsewhere erodes, leaving behind a pinnacle. Rocks in Goblin Valley date back to the late Jurassic period, around 160 million years ago.