A weekly feature provided by scientists at the Hawaiian Volcano Observatory. I tried to explain, but the caller hung up, more confused then ever. The first we can all agree on. When lava rises to the ground surface and forms lava flows, that is an eruption. The second meaning of eruption is less obvious.
Nothing leaves, except for gas and perhaps small bits of spatter.
No one questioned that this was an eruption. We don't, either. The rationale is simple but not obvious. So, whether or not a lava flow goes out of the crater is immaterial. There have been times during this long eruption, most recently between January 31 and February 23, when no lava was visible anywhere.