The lake partly fills a nearly NUMBER@1 foot -LRB- NUMBER@2 m -RRB- deep caldera that was formed around NUMBER@3 -LRB- ± NUMBER@4 -RRB- BC by the collapse of the volcano LOCATION@1 .

The lake partly fills a nearly NUMBER@5 feet -LRB- NUMBER@6 meters -RRB- deep caldera that was formed by the collapse of the volcano , LOCATION@1 .
