Additional Report for Malinao

Seismic and geothermal activity at Malinao

Luzon, Philippines

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

04/1970 (CSLP 35-70) Reports of tremors and rumblings

08/1980 (SEAN 05:08) Small phreatic explosion

Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

04/1970 (CSLP 35-70) Reports of tremors and rumblings

Card 0919 (27 April 1970) Reports of tremors and rumblings

Father Hennessey reports by cable that there is a 'report (that) Mount Malinao, an extinct volcano 20 km NNW of Mayon, is becoming active.' Earth tremors 'ranging from Intensity 1 to 5' have occurred and 'deep rumblings' have been heard.

W. Ward cabled the following: 'Mount Malinao acting up, no eruption since prehistoric times.'

Malinao is located in southeastern Luzon. It is a stratovolcano with crescentic center of which the northern wall is failing. The inner crater walls are bare. There are two hot wells, Jigabo and Naglabong. At the latter well, the fumaroles had a highest temperature of 108°C in 1903.

Information Contacts: Rev. J.J. Hennessey, Manila Observatory, Manila, Philippines; W.T.T. Ward, U.S. 13th Air Force Historical Office, Clark Air Force Base, Manila, Philippines.

08/1980 (SEAN 05:08) Small phreatic explosion

A small phreatic explosion took place on 29 July from one of the pools of hot water in the Naglagbong thermal area, Tiwi geothermal field, at the E foot of Malinao. The explosion ejected hot mud and blocks up to 2/3 m in diameter. The ejecta reached heights of 150 m and fell as much as 350 m from the vent. One person received second-degree burns and two buildings were damaged, one a COMVOL seismic station.

Before the explosion the pool was 15 m in diameter and 4.3 m deep, with clear emerald-green water at a temperature of 85°C. As early as 6 July, the seismograph recorded unusual microseisms. Two hours before the explosion, geysering of muddy water was observed.

[The minor explosion from the Naglabong thermal area that ejected blocks in 1980 was probably due to water drawdown during development of the Tiwi geothermal field (Newhall, 1994, pers. comm.).]

Information Contact: O. Peña, COMVOL, Quezon City.