Basalt of Gertrude Creek


Facts


  • Official Name:
  • Seismically Monitored: No
  • Color Code: UNASSIGNED
  • Alert Level: UNASSIGNED
  • Elevation: 437m (1433ft)
  • Latitude: 58.04
  • Longitude: -156.14
  • Smithsonian VNum:
  • Nearby Towns:
    • Kanatak 33 mi (53 km) SE
    • Egegik 47 mi (75 km) NW
    • King Salmon 49 mi (78 km) NW
    • South Naknek 56 mi (90 km) NW
    • Bristol Bay Borough 56 mi (91 km) NW

Description

This feature is part of the Saddlehorn Creek Cluster of volcanoes, as defined by Hildreth and others (2004) [1] . From Hildreth and others (2004) [1] : "Basalt of Gertrude Creek makes up a 1-km-wide remnant of an ejecta cone and lava-flow apron that form a glacially smoothed domical swell about 5 km NE of Becharof Lake, near the trace of the Bruin Bay Fault [2] . Surviving outcrop has about 60 m of gentle relief and includes a 200-m-wide degraded crater now only 5 to 8 m deep, rimmed by brick-red scoria blocks and sheets of blobby agglutinate that are broken and frost-heaved into slabs. Outside the rim is a massive to finely vesicular, basaltic lava. The subalkaline high-alumina basalt (49.8% SiO2, 6.8% MgO) contains abundant small phenocrysts of olivine, clinopyroxene, and plagioclase, and inclusions (in olivine) of Cr-spinel. A slab of holocrystalline lava near the north rim gave a 40Ar/39Ar plateau age of 500 +/- 15 ka [3] ."

Name Origin

"Basalt of Gertrude Creek" is an informal name applied to the volcanic vent near Gertrude Creek, given by Hildreth and others (2004). Gertrude Creek is a local name, reported to the U.S. Geological Survey in 1952 (Orth, 1971).


References Cited

[1] Rear-arc vs. arc-front volcanoes in the Katmai reach of the Alaska Peninsula: a critical apprasial of across-arc compositional variation, 2004

Hildreth, Wes, Fierstein, Judy, Siems, D. F., Budahn, J. R., and Ruiz, Joaquin, 2004, Rear-arc vs. arc-front volcanoes in the Katmai reach of the Alaska Peninsula: a critical apprasial of across-arc compositional variation: Contributions to Mineralogy and Petrology, v. 147, n. 3, p. 243-275.

[2] Quaternary geologic map of the Mount Katmai quadrangle and adjacent parts of the Naknek and Afognak quadrangles, Alaska, 1993

Riehle, J. R., and Detterman, R. L., 1993, Quaternary geologic map of the Mount Katmai quadrangle and adjacent parts of the Naknek and Afognak quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I 2032, unpaged, 1 sheet, scale 1:250,000.

[3] Geochronology and eruptive history of the Katmai volcanic cluster, Alaska Peninsula, 2003

Hildreth, Wes, Lanphere, M. A., and Fierstein, Judy, 2003, Geochronology and eruptive history of the Katmai volcanic cluster, Alaska Peninsula: Earth and Planetary Science Letters, v. 214, n. 1-2, p. 93-114.

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