We’ve learned a lot in the last 25 years, especially when it comes to underwater volcanoes. When I began researching and writing Not by Fire but by Ice in 1991, scientists guestimated that there were 10,000 submarine volcanoes in the entire world.
Two years later, marine geophysicists discovered 1,133 previously unmapped underwater volcanoes off the coast of Easter Island.
And they were huge. (Still are.) Some of the newly-found volcanoes rose almost 1½ miles above the seafloor. Even then, their peaks remained about 1½ miles below the water’s surface. They’re packed into a relatively small area about the size of New York state.













