at the risk of thread-drift, when did these events occur, drew? up by Salal Ck?
cheers,
First off the main Plinth lava flow that created Keyhole Falls, and dates to 2350 BP (before present)
Second of all the Capricorn Creek and Devastator (No Good Creek) drainages have both produced slides resulting in blockages of Meager Creek and generating flood waves down the Lillooet. None of the historic ones have reached Pemberton townsite as significant floods, most fizzled out at Pemberton Meadows. The Neal Carter party that made FAs of these peaks in the 30s were able to travel up the floodplain of the Lillooet to the Meager Group in style partly because it had been scoured by such a wave a few years earlier. Prehistoric evidence (sediment cores from Lillooet Lake) indicate that these flood waves recur every few hundred years at a size large enough to reach Pemberton townsite. We're overdue for a new one, BTW.