Tidal triggering of seismic and volcanic phenomena during the 1879–1880 eruption of Islas Quemadas volcano in El Salvador, Central America

The Islas Quemadas dome in Lake Ilopango, El Salvador, was extruded during December 1879 to March 1880. The eruption took place in six distinct periods, five of which began near fortnightly minima in the amplitude of the semidiurnal solid earth tide. An earthquake swarm preceded dome extrusion. Felt earthquakes were carefully recorded during a two-day period preceding a destructive main shock that occurred on December 27, 1879. During this foreshock sequence the periods of highest earthquake activity occurred at times of maxima and minima in semidiurnal solid-earth tide. The four largest earthquakes, including the main shock, occurred at maxima in the semidiurnal tide.