Wednesday, April 05, 2006

Mount Arayat (Glossary)

Rising majestically over an expansive flat plain, Mount Arayat commands views from all directions over much of Central Luzon.

Located between east and northeast from Angeles City, about the same distance from the latter that Pinatubo extends to the west-southwest from that city.

Once famed forests have lost a good bit of their cover but still provide refuge to guerillas as they have through much of history. The mountain has been an important base for underground military activity since World War II.

Spiritually-inclined people have also made pilgrimages to this mountain since the earliest memories often walking many miles to commune with fellow seekers on its slopes. Here is the home of Apung Sinukuan, the sun god. Herbs from this mountain are believed to have special healing qualities. The name of Arayat indicates that it was located towards the East in the geomantic view of the ancient Kapampangans who live around its slopes.

Unlike Pinatubo which is difficult or impossible to make out from most densely-populated areas of Luzon, Arayat's imposing profile is inescapable.

Mt. Arayat rises over the flat plains of Pampanga. Picture taken from Clark Field. (Source: Brian Rueger,

However, Arayat is likely a secondary or back arc to the Western Central Luzon arc that includes Mt. Pinatubo to the West. Pinatubo's basalt magmas though are more like those of Arayat than the neighboring volcanoes with which it forms the same primary arc.

Volcanologists believe that Pinatubo's magmas involve a mixing of the basement rock Zambales Ophiolite and the secondary arc mantle. Possibly the sub arc mantle is even that related directly to Arayat.

Arayat's last major eruption is something of a mystery. It is known to have been "active" during the Holocene (present) period, but the exact nature of this actiivty is not well-known.

Paul Kekai Manansala


Pallister, John S. , Richard P. Hoblitt, Gregory P. Meeker, Roy J. Knight, and David F. Siems. "Magma Mixing at Mount Pinatubo: Petrographic and Chemical Evidence from the 1991 Deposits", Fire and Mud, 1991,