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Folsoms Bluff description and information


Type:Lava and ejecta of glaciated vent complex
Most Recent Activity:
Seismically Monitored: No
Elevation: 3799 ft (1158 m)
Latitude: 58.40881° N
Longitude:155.21516° W
Quadrangle:Mt Katmai
CAVW Number:
Pronunciation: Sound file
Nearby towns:King Salmon 56 mi (89 km) NW
Karluk 64 mi (103 km) SE
Kanatak 65 mi (105 km) SW
Bristol Bay Borough 68 mi (109 km) NW
Anchorage 268 mi (431 km) NE
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]: "Folsoms Bluff (Knob 3800), an inhomogenously andesitic (55-60% SiO2) funnel-shaped vent complex, is a multi-lobate glassy lava mass 500 m wide and 200 m high that makes up part of the canyon wall just 2 km east of Fenners Saddlehorn. Marked by steep flow foliation and several sets of inclined, subhorizontal, or steeply curving glassy columns indicative of ice-contact emplacement, the lava has a brecciated base that overlies 8 to 15 m of stratified, poorly sorted proximal fallout, which includes scoria bombs to 75 cm and blocks of basement granitoid to 30 cm. This basal fallout drapes a steep paleoslope and extends uphill into a mass of agglutinated lithic-rich rubble more than 20 m thick, probably vent fill largely concealed by the overlying lava. All lithologies contain abundant small plagioclase phenocrysts as well as olivine, clinopyroxene, orthopyroxene, and magnetite. Its canyon-wall setting and eruptive facies relations suggest that, like Fenners Saddlehorn nearby, this undated glassy unit is younger than the three ridge-capping members of the cluster."
Rear-arc vs. arc-front volcanoes in the Katmai reach of the Alaska Peninsula: a critical apprasial of across-arc compositional variation, 2004
citation imageHildreth, 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.

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