Disruption of the mauna loa magma system by the 1868 hawaiian earthquake: geochemical evidence.

To test whether a catastrophic earthquake could affect an active magma system, mean abundances (adjusted for "olivine control") of titanium, potassium, phosphorus, strontium, zirconium, and niobium of historic lavas erupted from Mauna Loa Volcano, Hawaii, after 1868 were analyzed and were found to decrease sharply relative to lavas erupted before 1868. This abrupt change in lava chemistry, accompanied by a halved lava-production rate for Mauna Loa after 1877, is interpreted to reflect the disruptive effects of a magnitude 7.5 earthquake in 1868. This interpretation represents a documentable case of changes in magmatic chemical variations initiated or accelerated by a major tectonic event.

Holocene eruptive activity of el chichon volcano, chiapas, Mexico.

Geologic and radiometric-age data indicate that El Chichón was frequently and violently active during the Holocene, including eruptive episodes about 600, 1250, and 1700 years ago and several undated, older eruptions. These episodes, involving explosive eruptions of sulfur-rich magma and associated dome-growth processes, were apparently separated by intervals of approximately 350 to 650 years. Some of El Chichón's eruptions may correlate with unusual atmospheric phenomena around A.D. 1300 and possibly A.D. 623.