A group of scientists in Oregon were on a routine mission to recover underwater monitoring instruments in late July when they noticed the area around Axial Seamount, an undersea volcano they had been observing, was unrecognizable from the previous year.

"We couldn't find our markers or monitoring instruments or other distinctive features on the bottom," Bill Chadwick, a geologist with Oregon State University, told AFP (Agence France-Presse).

"At first we were really confused, and thought we were in the wrong place," Chadwick told MSNBC. "Finally we figured out we were in the right place but the whole seafloor had changed, and that's why we couldn't recognize anything. All of a sudden it hit us that, wow, there had been an eruption. So it was very exciting."

The discovery of the eruption -- which was determined to have taken place on April 6 -- was all the more exciting for the fact that Chadwick and colleagues in Oregon and New York had predicted it in advance.

The scientists have been monitoring Axial Seamount, a volcano 3000 feet above the sea floor and 250 miles off the coast of Oregon, since it last erupted in 1998.

Chadwick co-authored a study in 2006 that predicted the volcano would erupt again before 2014. He and his colleagues have been using underwater monitoring instruments to observe the inflation and deflation movements of the sea floor, patterns they believed to be indicators of an imminent eruption.

The data from Axial Seamount's recent volcanic activity will provide the first long-term picture of an underwater volcano from one eruption to the next.  The April 6 eruption also marks the first accurate prediction of a subsea volcanic eruption.

"The acid test in science -- whether or not you understand a process in nature -- is to try to predict what will happen based on your observations," Chadwick told AFP.

"Now we can build on that knowledge and look to apply it to other undersea volcanoes -- and perhaps even volcanoes on land."