Iriga

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 13.457°N
  • 123.457°E

  • 1196 m
    3923 ft

  • 273041
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

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Mount Iriga is a small stratovolcano that rises to 1196 m immediately SW of Lake Buhi. The dominantly andesitic stratovolcano has satellitic cinder cones of basaltic composition. A large breached crater that opens to the SE was formed as a result of a major debris avalanche that buried several villages and formed a broad hummocky deposit that extends across the plain south of Lake Buhi. This catastrophic event was at one time considered to have occurred during 1628 CE, but later work has shown that the collapse and eruption occurred earlier at some unknown date during the Holocene. The avalanche was followed by phreatic explosions that created a small crater at the base of the scarp.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1628 ] [ Unknown ] Discredited    

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.



Synonyms
Asog
Mount Iriga is a 1196-m stratovolcano whose most prominent feature is a large horseshoe-shaped caldera that is breached to the SE. It was formed by a massive volcanic landslide during an eruption that at one time was considered to have most likely occurred in 1628 AD, but was later found to have occurred earlier at some unknown time during the Holocene. The hilly terrain in the foreground, encloses small ponds on the surface of the debris-avalanche deposit.

Photo by Chris Newhall (U.S. Geological Survey).
Collapse of the summit and flanks of volcanoes during major volcanic landslides creates large horseshoe-shaped depressions that open in the direction of the landslide. This 2.1 x 3.5 km horseshoe-shaped caldera at Iriga volcano in the Philippines was produced by a massive landslide during the Holocene. The resulting debris avalanche traveled more than 10 km to the SE and flowed into Lake Buhi at the upper right. This view is from the south, with the summit of Iriga at the extreme left.

Photo by Chris Newhall (U.S. Geological Survey).
The small crater at left-center was formed at the base of the headwall of a massive landslide during an eruption during the Holocene. This view looks west into the horseshoe-shaped caldera created during the collapse, with the summit of Iriga in the background. The headwall above the crater is 600 m high.

Photo by Chris Newhall (U.S. Geological Survey).
The entire foreground area in this view of Iriga volcano in the Philippines is a massive, 1.5 cu km debris-avalanche deposit formed by a Holocene landslide from Iriga volcano in the Philippines. This view from the SE shows the typical hummocky topography of debris-avalanche deposits. Many of the darker areas are tree-covered hummocks; the irregular topography of the avalanche-deposit also encloses many small ponds.

Photo by Chris Newhall (U.S. Geological Survey).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Aguila L G, Newhall C G, Miller C D, Listanco E L, 1986. Reconnaissance geology of a large debris avalanche from Iriga volcano, Philippines. Philippine J Volc, 3: 54-72.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

PHIVOLCS, 2004-. Volcanoes. http://www.phivolcs.dost.gov.ph/Volcanolist/.

Volcano Types

Stratovolcano
Cinder cone(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Andesite / Basaltic Andesite
Basalt / Picro-Basalt

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
3,712
142,254
1,159,509
4,399,866

Affiliated Databases

Large Eruptions of Iriga Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.