Improved Isopachs for the Glass Creek Tephra, Inyo Volcanic Chain, California

The Glass Creek tephra erupted in 1350 C.E. (Millar et al., 2006) and is the last of the series of four contemporaneous tephra eruptions from three vents of the Inyo volcanic chain (Miller, 1985). Miller (1985) provides isopachs for the tephra and estimates a volume of 0.10 km³, whereas the methods of Fierstein and Nathenson (1992) give a volume of 0.13 km³.

Bursik and Sieh (2013) published measurements of thickness and used a cubic spline methodology to create isopachs. Their volume estimate is 0.08 km³. The projected thickness of their isopachs is 254 cm at zero area. Their highest measured thickness is 578 cm at about 1.5 km from the vent, and their isopachs do not include thickening at a higher rate in the proximal area.

Maps of the thickness measurements and of the field locations made by Miller (1985) have been obtained and most of his measurements have been recovered and documented with locations. Combining the data sets results in a better overall coverage than either of the original studies. The 100-cm isopach is more similar to that of Miller (1985) than that of Bursik and Sieh (2013). The most distal isopach that is well defined by the data is 10 cm, whereas Miller (1985) could only close the 50-cm isopach. The revised volume is 0.087 km³.

Bursik, M., and Sieh, K., 2013, Digital database of the Holocene tephras of the Mono-Inyo Craters, California: U.S.G.S. Data Series 758, 6 p.

Fierstein, J., and Nathenson, M., 1992, Another look at the calculation of fallout tephra volumes: Bul. Volc., v. 54, p. 156-167.

Millar, C.I., King, J.C., Westfall, R.D., Alden, H.A., and Delany, D.L., 2006, Late Holocene forest dynamics, volcanism, and climate change at Whitewing Mountain and San Joaquin Ridge, Mono County, Sierra Nevada, CA, USA: Quat. Res., v. 66, p. 273–287.

Miller, C.D., 1985, Holocene eruptions at the Inyo volcanic chain, California: Implications for possible eruptions in Long Valley caldera: Geology, v. 13, p. 14–17.