Many places, many times.
yes it is a underwater volcano
Underwater
Sure if they erupt underwater or in an uninhabited place on the earth
Crater Lake Volcano, also known as Mount Mazama had a massive eruption approximately 7,700 years ago, forming a deep caldera. The last known eruption took place about 4,800 years ago underwater.
No, the Stromboli volcano is on an island.
seamounts
An underwater volcano is called a submarine volcano.
One example of an underwater volcano is Axial Seamount, located off the coast of Oregon in the United States. It is an active submarine volcano that rises about 1,300 meters from the sea floor.
A caldera...
seamount
You get away as soon as possible. Get into a far away state from the underwater volcano. If your in Texas you go into Colorado and so on.
The volcano erupted in Iceland but the ash from the volcano covered most of Europe and Asia.