N_Fiddledog N_Fiddledog:
That is disturbing. What could possibly have caused it? Surely not all the underwater volcanoes honeycombed through that area.

We've heard for years how the volcano under that glacier could erupt causing the glacier to slip into the ocean, cause sea level to rise 2 feet. It hasn't. Now we learn there's a giant cavern under the glacier. I guess melting the bottom of the glacier didn't cause it to slip into the ocean.
In 2010 a volcano under a glacier in Iceland erupted. Coastal cities were not flooded. Don't ask me to pronounce it, copying from a news article it was called "Eyjafjallajökull". Volcanic ash disrupted air travel, but no rise in sea level.