Folsoms Bluff


Facts


  • Official Name:
  • Seismically Monitored: No
  • Color Code: UNASSIGNED
  • Alert Level: UNASSIGNED
  • Elevation: 1158m (3799ft)
  • Latitude: 58.40881
  • Longitude: -155.21516
  • Smithsonian VNum:
  • 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
    • Igiugig 68 mi (109 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] : "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."

Name Origin

"Folsoms Bluff" is an informal name given by Hildreth and others (2004).


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.

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