A landslide in Tertiary marine shale with superheated fumaroles, Coast Ranges, California

Geology
By: , and 

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Abstract

In August 2004, a National Forest fire crew extinguished a 1.2 ha fire in a wilderness area ~40 km northeast of Santa Barbara, California. Examination revealed that the fire originated on a landslide dotted with superheated fumaroles. A 4 m borehole punched near the hottest (262 °C) fumarole had a maximum temperature of 307 °C. Temperatures in this borehole have been decreasing by ~0.1 °C/d, although the cooling rate is higher when the slide is dry. Gas from the fumaroles and boreholes is mostly air with 3–8 vol% carbon dioxide and trace amounts of carbon monoxide, methane, ethane, and propane. The carbon dioxide is 14C-dead. The ratios of methane to ethane plus propane [C1/(C2 + C3)] range from 3.6 to 14. Carbon isotope values for the CO2 range from −14‰ to −23‰ δ13C. 3He/4He values range from 0.96 to 0.97 times that of air. The anomalous heat is interpreted to be due to rapid oxidation of iron sulfide augmented by combustion of carbonaceous matter within the formation.

Publication type Article
Publication Subtype Journal Article
Title A landslide in Tertiary marine shale with superheated fumaroles, Coast Ranges, California
Series title Geology
DOI 10.1130/G25285A.1
Volume 36
Issue 12
Year Published 2008
Language English
Publisher GeoScience World
Contributing office(s) Geosciences and Environmental Change Science Center, Volcano Hazards Program, Volcano Science Center
Description 4 p.
First page 959
Last page 962
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