그리그산

The summit of Mount Griggs towers above Knife Creek on the NE side of the Valley of Ten Thousand Smokes. The volcano is offset west of the NE-trending alignment of volcanoes in the Katmai area. The broad stratovolcano, formerly known as Knife Peak, consists of a late-Pleistocene edifice with glacial valleys on the north that was truncated on its SW side by an early Holocene collapse. A Holocene volcano was subsequently constructed within the 1.5-km-wide scarp left following a large SW-flank debris avalanche. Nested cones with three concentric craters mostly fill the scarp, and thick, blocky lava flows cover the SW flanks below the collapse scarp. In contrast to the more silicic centers of the Katmai area along the crest of the range, lava flows from Griggs are dominantly andesitic in composition, and dacitic lava flows are uncommon. No eruptions have been observed, but noisy fumarolic jets near the summit can be heard from the valley floor.