The horseshoe-shaped string of active volcanos bounding the Pacific Ocean has lived up to its "Ring of Fire" name in the past month, sparking mass evacuations in Indonesia and Vanuatu and now setting parts of southwestern Japan on edge. The 450 or so volcanos that make up the "Ring of Fire" are an outline of where the massive Pacific Plate is grinding against other plates that form the Earth's crust, creating a 40,000-kilometer (25,000-mile) -long zone prone to freq…