The flowing lava forms deltas into the sea that can extend hundreds of feet in a matter of days. The deltas build out and then collapse under their own weight, forming a foundation for subsequent flow. These deltas begin with surface lava flow that crawls resolutely to the water, impeded only by gravity. As the flows mature, they usually harden on their surfaces, and the lava moves out to the ocean through tubes that run below the crust. These tubes emerge at or below the waterline.
Spectacular results occur from the meeting of the powerful natural forces of ocean and volcano.
A steam plume rises as the water contacting the lava instantly evaporates. But explosions called tephra jets also occur, in which the lava actually bursts into pieces of glass. The explosions are especially powerful when large waves wash in, exposing large areas of the lava to water, or when sections of the delta collapse, trapping water underneath. Viewing conditions change all the time, even minute by minute. What is happening right now is that something happened in August in the plumbing of the tube.