How Tourist Garbage Causes Yellowstone's Morning Glory To Change Color

Decades ago, the Morning Glory pool at Yellowstone National Park was a gorgeous deep blue. But because tourists have thrown coins, rocks, and trash into it for years, the spring has now turned into a sickly yellowish green. Now, a new optics study is shedding light on the pool's unfortunate change of color. »2/11/15 4:20pm2/11/15 4:20pm