The images of the Monowai volcano near Tonga were gathered from a research ship during a seabed survey last year, researchers said.
Scientists from Oxford University said they recorded huge changes in the height of the volcano in just two weeks.
The findings are "a wake-up call that the sea-floor may be more dynamic than we previously thought," researcher Tony Watts told the BBC.
"I've spent my career studying the seabed and have generally thought it pretty stable so it's stunning to see so much change in such a short space of time," he said.
In just two weeks, researchers said, one part of the volcano's summit had collapsed by as much as 62 feet while new lava flows had raised another area by 260 feet.
Only Vesuvius and Mount St. Helens have recorded larger growth rates, they said.
The findings are "a reminder of how rapidly geological processes such as submarine landsliding and volcanism can occur," the scientists said.