Gas Rocks, the reported activity

Event Name : Gas Rocks Dome 600

Start: 23300 (± 1200 Years)

Years BP Ar/Ar

Lava flow:
Lava dome:

Eruption Type:	Explosive
Eruption Product:	dacite
Chem	Yes
Other	felsic

Description: From Hildreth and others (2006): "The larger domes, Domes 600 and 700 (figs. 10, 12 [in original text]), have 180 and 210 m relief, respectively, above the lake. Dome 600 appears to be a single simple extrusion, as shown by the steep jointing that flares slightly outward toward the top of its northeast face (fig. 13 [in original text]). Nonetheless, a pair of lava flows, each 10 to 15 m thick, extends to the shoreline from the foot of that face (fig. 13 [in original text])."

"Little or no glassy or pumiceous carapace remains on any of the domes, which were all completely submerged and scoured by glacial ice."

Hildreth and others (2006) estimate a volume of 15 million m cubed for Dome 600.

"We [Hildreth and others, 2006] determined two 40Ar/39Ar ages on groundmass concentrates from samples of The Gas Rocks dacite (fig. 9; table 2 [in original text]). Sample U-1, from the small North Point Dome (fig. 3B [in original text]), yielded a weighted-mean plateau age of 25.7+/-1.4 ka, and sample U-2, from Dome 600, 23.3+/-1.2 ka. At their extremes, the two error envelopes just overlap, although nothing on the ground is known to contradict a younger age for the larger dome. Because of their petrographic and compositional similarity, it cannot be excluded that the three domes are essentially contemporaneous, plausibly fed by a common dike, the northwesterly strike of which would be similar to the present-day plate-convergence direction (which might in turn influence the direction of maximum horizontal compression)."