How are underwater volcanoes different from volcanoes that are above sea level?
Submarine volcanoes are very different from the volcanoes that are above sea level. Water has a higher pressure than air. This higher pressure can cause an underwater explosive volcanic eruption. One famous example of an underwater explosive eruption is Surtsey, a new volcano off the south shore of Iceland. When Surtsey erupted it punched through the sea and became an island! Which is the biggest volcano? The biggest volcano in the world is probably Mauna Loa, in Hawaii. It rises off of the seafloor to 13,000 feet above sea level or about 29,000 feet above the seafloor. Another huge volcano is Mt. Etna on the island of Sicily, in Italy. How old is the oldest volcano? The oldest volcano is probably Etna and that is about 350,000 years old. Most of the active volcanoes that we know about seem to be less than 100,000 years old. Volcanoes grow because lava or ash accumulates on the volcano, adding layers and height. What is the longest period of time a volcano has been known to be active?
