Earthquakes and Carbon Dioxide Beneath Mammoth Mountain, California

Abstract

INTRODUCTION Anyone reading a newspaper or watching television in late August, 1995 learned that carbon dioxide gas is killing trees on the flanks of Mammoth Mountain, a ski resort on the western boundary of Long Valley caldera in eastern California. Much to the consternation of residents in the nearby town of Mammoth Lakes, some of the more sensationalist media coverage gave the mistaken impression that deadly CO2 prompted local evacuations and portended an imminent volcanic eruption. This article places the CO2 emissions described by Farrar et al . (1995) in the context of unrest beneath Long Valley caldera and vicinity that began over 15 years ago (Hill et al ., 1985; Bailey and Hill, 1990; Langbein et al ., 1993; Rundle and Hill, 1988). It focuses in particular on the spatial-temporal evolution of seismicity beneath Mammoth Mountain and evidence that the CO2 emissions are slowly developing, passive phenomena related to magmatic processes activated...