2010 showed what kinds of impacts can occur when a volcano erupts in Iceland. [1]
> In response to concerns that volcanic ash ejected during the 2010 eruptions of Eyjafjallajökull in Iceland would damage aircraft engines, the controlled airspace of many European countries was closed to instrument flight rules traffic, resulting in what at the time was the largest air-traffic shut-down since World War II.
> On 16 April 2010, 16,000 of Europe's usual 28,000 daily scheduled passenger flights were cancelled and on the following day 16,000 of the usual 22,000 flights were cancelled. By 21 April 95,000 flights had been cancelled.
> IATA stated that the total loss for the airline industry was around US$1.7 billion (£1.1 billion, €1.3 billion).
Eyjafjallajökull was a special case, it was not an oceanic blast, but a blast under a glacier. Fjallajökull means "glacier mountain". The blast flash-melted several tones of ice, which caused the lava to cool rapidly forming the ash cloud. If my memory serves, the glacier was in the caldera itself.
But the effect would be very similar. The water would vaporize and create an aerosol of ash.
> In response to concerns that volcanic ash ejected during the 2010 eruptions of Eyjafjallajökull in Iceland would damage aircraft engines, the controlled airspace of many European countries was closed to instrument flight rules traffic, resulting in what at the time was the largest air-traffic shut-down since World War II.
> On 16 April 2010, 16,000 of Europe's usual 28,000 daily scheduled passenger flights were cancelled and on the following day 16,000 of the usual 22,000 flights were cancelled. By 21 April 95,000 flights had been cancelled.
> IATA stated that the total loss for the airline industry was around US$1.7 billion (£1.1 billion, €1.3 billion).
[1] https://en.wikipedia.org/wiki/Air_travel_disruption_after_th...