Agrigan
Stratovolcano in United States
Key Facts
Elevation
965 m (3,166 ft)
Type
Stratovolcano
Location
18.770°, 145.670°
Region
Mariana Volcanic Arc
Rock Type
Basalt / Picro-Basalt
Tectonic Setting
Subduction zone
Location
Loading map...
Overview
The highest of the Marianas arc volcanoes, Agrigan contains a 500-m-deep, flat-floored caldera. The elliptical island is 8 km long; its summit is the top of a massive 4000-m-high submarine volcano. Deep radial valleys dissect the flanks of the thickly vegetated stratovolcano.
The elongated caldera is 1 x 2 km wide and is breached to the NW, from where a prominent lava flow extends to the coast and forms a lava delta. The caldera floor is surfaced by fresh-looking lava flows and also contains two cones that may have formed during the only historical eruption in 1917. This eruption deposited large blocks and 3 m of ash and lapilli on a village on the SE coast, prompting its evacuation.
Volcanic Hazards & Risk Assessment
Primary Hazards
- Pyroclastic flows
- Lava flows
- Volcanic bombs and ballistics
- Lahars and mudflows
Risk Level
Geological Composition & Structure
Rock Types
Tectonic Setting
Age & Formation
Eruption Statistics & Analysis
| Metric | Value | Global Ranking | Significance |
|---|---|---|---|
| Total Recorded Eruptions | Unknown | Low | Moderately active volcano |
| Maximum VEI | VEI Unknown | Minor | Local impact potential |
| Recent Activity | 109 years ago | Historical | Historically active |
Monitoring & Alert Status
Monitoring Networks
Current Status
Nearby Volcanoes in Northwestern Pacific Volcanic Regions
Quick Info
- •Smithsonian ID: 284160
- •Evidence: Eruption Observed
- •Epoch: Holocene
About the Photo
Agrigan is the highest of the Marianas arc volcanoes, seen here from the south. The island is 8 km long and its summit is the top of a large 4-km-high submarine volcano. The summit caldera is 1 x 2 km wide and 500 m deep, and the vegetated flanks consist almost entirely of pyroclastic deposits that are more than 100 m thick on the SW flank.
Photo by Richard Moore, 1990 (U.S. Geological Survey).
Authority Sources
Related Volcanoes
Basic Information
This page shows basic data from the Smithsonian Global Volcanism Program. For more detailed information, visit the official Smithsonian page.