When a volcano erupts on the sea floor, and continues to erupt slowly for thousands of years, it eventually results in formation of an island. This is exactly how the Hawaiian Islands - extending over a distance of around 1,500 miles in the North Pacific Ocean, were formed. As of today, there exist 500 active volcanoes on the planet, of which at least 50 are notorious for frequent eruptions. In fact, the United States of America alone is home to 50 active volcanoes, of which 5 are found in the state of Hawaii.