Eruptions of Pavlof Volcano, Alaska, and their Possible Modulation by Ocean Load and Tectonic Stresses: Re-evaluation of the Hypothesis Based on New Data from 1984–1998

Thirteen of sixteen magmatic eruptions of Pavlof Volcano in nine of the years from 1973 to 1998 have occurred between September 9 and December 29. Volumes of erupted material range from 0.3 to 16 2 106 m3 (dense rock equivalent). A significant correlation exists between the eruptions and yearly nontidal variations in sea level and may result from ocean loading. Calculated volume changes beneath the volcano due to ocean loading are from 0.02 to 0.6 times eruption volumes, and it is postulated that the volcano acts as a long-period (several months) volume strainmeter, with lava being preferentially erupted when strain beneath the volcano is compressive. Previous observations of a tilt reversal, and new observations of tectonic activity and eruptions in the spring and summer of 1986, also suggest tectonic modulation of eruptions. The volcano appears to be responsive to small, slow changes in ambient stresses or strains, and these changes may modify or trigger eruptions.