Found the following at
http://www.volcano.si.edu/world/volc...=var#sean_0909
"Most explosions ejected a small number of very vesicular bombs that were typically 2-4 m in diameter but sometimes reached 6-8 m. Some of the bombs were ejected to heights of 500 m or more, possibly to as much as 1 km."
and
"incandescent bombs were ejected to ~600 m above the summit"
As I remarked previously on the wisdom of overflying Erebus, meeting a 2 meter rock at above the mountain could spoil your whole day. What did you say the LSALT was? 12,448 + 3,280 = 15,728 A bit close for comfort over flying the mountain. Lack of planning? You betcha. Pilots fault? Not on your nelly.
Damn good reason the RNC route runs down the sound. Pity the airline didn't follow it. And shows Mahon had good reason to make his comments on Erebus over flight.