Volcanoes of the World
About 550 volcanoes have erupted on Earth's surface since recorded history; about 60 are active each year. Far more have erupted unobserved on the ocean floor. Most volcanoes exist at the boundaries of Earth's crustal plates, such as the famous Ring of Fire that surrounds the Pacific Ocean plate. Fifty volcanoes have erupted in the United States since recorded history, and the United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes.