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What Most erupting volcanoes are found where tectonic plates slide under each other to form undersea trenches as deep as 2.5 miles. As one plate is pushed deeper, mounting pressure and temperature melt the crust into magma that bubbles up to create a line of exploding mountaintops–like Mt. Rainier, which last blew its top in the mid-1800s, and Hawaii’s Mauna Loa, the world’s largest active volcano. More than 75 percent of the globe’s 1,500 active volcanoes lie in the Pacific Ring of Fire, the horseshoe-shaped area stretching from New Zealand north to Japan, east to Alaska, and south along the U.S. West Coast and the Andes.
Where Stromboli Volcano, Sicily. This 3,000-foot island volcano has been continuously spurting incandescent lava–sometimes hundreds of feet into the air–for more than 2,400 years. When conditions allow (i.e., the mountain isn’t erupting over the trail), hikers can safely summit for a front-row seat. Guides are required above 1,300 feet. parks.it