Basalt of Gertrude Creek
Facts
- Seismically Monitored: No
- Color Code: UNASSIGNED
- Alert Level: UNASSIGNED
- Elevation: 437m (1433ft)
- Latitude: 58.04
- Longitude: -156.14
- Smithsonian VNum:
- Pronunciation:
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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
Distance from Anchorage: 309 mi (498 km)
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).