About Gemini-Oscostar
Gemini-Oscostar is a stratovolcano rising to -33 meters (-108 feet) in Vanuatu's Southwestern Pacific Volcanic Regions. It last erupted in 1996 CE, and volcanologists consider it an active volcanic system. The volcano has produced 1 recorded eruption, with a maximum Volcanic Explosivity Index (VEI) of 1.
Geography & Climate
Gemini-Oscostar is located in Vanuatu, within the Vanuatu Volcanic Arc of the broader Southwestern Pacific Volcanic Regions. Situated at 20.96° S, 170.13° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. With an elevation of -33 meters — below sea level — Gemini-Oscostar is a submarine or submerged volcanic feature. Submarine volcanoes make up the majority of Earth's volcanic activity, though most eruptions go unobserved beneath the ocean surface. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.
Geological Context
Gemini-Oscostar is situated along a rift zone, where tectonic plates are pulling apart. As the crust thins and fractures, magma rises to fill the gap, creating volcanic activity. Rift volcanism typically produces more fluid lava flows rather than explosive blasts, which means communities near Gemini-Oscostar in Vanuatu generally face slower-moving hazards like lava flows and ground fissures rather than sudden pyroclastic events. However, rift volcanoes can still generate significant ash emissions and gas releases that affect local air quality. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.
Eruption History Summary
Gemini-Oscostar has 1 recorded eruption in the geological database, spanning from 1996 CE to 1996 CE. The most powerful recorded event was a gentle, effusive event in 1996 CE, reaching VEI 1 on the Volcanic Explosivity Index. The most recent eruption in 1996 CE places this volcano within the modern era of volcanological observation.
GVP Reference Summary
The submarine Gemini-Oscostar volcanic field lies near the southern end of the Vanuatu (or New Hebrides) Volcanic Arc, ~100 km S of Aneityum Island. Water discoloration and bursts of very dark water were observed from Oscostar seamount (also known as Eastern Gemini) from a passing ship on 18 February 1996. Overflights as late as 22 February noted periodic explosions that ejected black material to about 20 m above sea level. It consists of an elongated NNE-SSW-trending ridge of submarine volcanoes with satellitic cones. Several basaltic samples and one andesitic rock dredged in 1989 were described as glassy, vesicular, and extremely fresh.
— Smithsonian Institution, Global Volcanism Program
1 Recorded Eruption
| Year | VEI | Type | Area |
|---|---|---|---|
| 1996 | 1 | Confirmed Eruption | — |
Real-Time Data
USGS Alert Level
Thermal Anomalies
Frequently Asked Questions About Gemini-Oscostar
Is Gemini-Oscostar an active volcano?+
Yes, Gemini-Oscostar is considered an active volcano. Its most recent eruption was in 1996 CE. The volcano is monitored by geological agencies, and its activity status is based on observed eruptions within recorded history.
When did Gemini-Oscostar last erupt?+
The most recent recorded eruption of Gemini-Oscostar occurred in 1996 CE with a Volcanic Explosivity Index (VEI) of 1. The eruption was classified as a "Confirmed Eruption." Gemini-Oscostar has 1 recorded eruption in total.
How high is Gemini-Oscostar?+
Gemini-Oscostar has a summit elevation of -33 meters (-108 feet) above sea level. With an elevation of -33 meters (below sea level), this is a submarine or submerged volcanic feature.
What type of volcano is Gemini-Oscostar?+
Gemini-Oscostar is classified as a Stratovolcano. Stratovolcanoes (also called composite volcanoes) are steep, conical volcanoes built up by many layers of hardened lava, tephra, and volcanic ash. They are among the most common and dangerous types, known for explosive eruptions.
Where is Gemini-Oscostar located?+
Gemini-Oscostar is located in Vanuatu, in the Southwestern Pacific Volcanic Regions. More specifically, it lies within the Vanuatu Volcanic Arc. Its exact coordinates are -20.957° latitude, 170.130° longitude.
Is it safe to visit Gemini-Oscostar?+
Visiting Gemini-Oscostar requires checking current volcanic activity and alert levels. As an active volcano with eruptions as recent as 1996 CE, conditions can change rapidly. Always consult local geological authorities and follow official warnings before visiting. Many active volcanoes have designated safe viewing areas and guided tour options.
