In 1867, Frank Fouqu? on a visit to Terceira to study the submarine eruptions on Serreta, wrote of a lava tunnel at the entrance to the Guilherme Moniz caldera, referring to it as one of the more beautiful that he had visited.
32.
An estimated 75 % of the total volcanic eruptive volume is generated by submarine eruptions near mid ocean ridges alone, however because of the problems associated with detecting deep sea volcanics, they remained virtually unknown until advances in the 1990s made it possible to observe them.
