About Kao
Kao is a stratovolcano rising to 1,009 meters (3,311 feet) in Tonga's Tonga-Kermadec Volcanic Regions. Its last known eruption was in 1847 CE. The volcano has produced 1 recorded eruption, with a maximum Volcanic Explosivity Index (VEI) of 2.
Geography & Climate
Kao is located in Tonga, within the Tofua Volcanic Arc of the broader Tonga-Kermadec Volcanic Regions. Situated at 19.67° S, 175.02° W in the Southern Hemisphere, the volcano lies within a tropical climate zone. With a summit elevation of 1,009 meters above sea level, Kao is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.
Geological Context
Kao sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Tonga near Kao, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is andesite / basaltic andesite, 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
Kao has 1 recorded eruption in the geological database, spanning from 1847 CE to 1847 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1847 CE, reaching VEI 2 on the Volcanic Explosivity Index.
GVP Reference Summary
The symmetrical Kao rises steeply from the ocean about 6 km N of Tofua Island in Tonga. It is elongated NNE-SSW and, with the exception of a small flat area on the SSW coast, rises at angles exceeding 35° to the summit, which has a series of small coalescing craters. The lower flanks of the basaltic andesite volcano are densely jungled, but the upper slopes are almost vegetation free. There are no fresh-looking lava flows, although the absence of sufficient time for erosion to produce deep gullies or high sea cliffs suggests a very recent origin. A missionary on a ship anchored at Tofua reported that "smoke" was "pouring forth" from Kao on 10 July 1847.
— Smithsonian Institution, Global Volcanism Program
1 Recorded Eruption
| Year | VEI | Type | Area |
|---|---|---|---|
| 1847 | 2 | Confirmed Eruption | — |
Real-Time Data
USGS Alert Level
Thermal Anomalies
Frequently Asked Questions About Kao
Is Kao an active volcano?+
Kao is classified as active based on credible evidence of past eruptions. Although its last known eruption was in 1847 CE, volcanologists consider it capable of erupting again.
When did Kao last erupt?+
The most recent recorded eruption of Kao occurred in 1847 CE with a Volcanic Explosivity Index (VEI) of 2. The eruption was classified as a "Confirmed Eruption." Kao has 1 recorded eruption in total.
How high is Kao?+
Kao has a summit elevation of 1,009 meters (3,311 feet) above sea level. At 1,009 meters, it is a moderately sized volcanic peak, roughly comparable to Mount Vesuvius (1,281m).
What type of volcano is Kao?+
Kao 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 Kao located?+
Kao is located in Tonga, in the Tonga-Kermadec Volcanic Regions. More specifically, it lies within the Tofua Volcanic Arc. Its exact coordinates are -19.668° latitude, -175.016° longitude.
Is it safe to visit Kao?+
Kao can generally be visited, but as with any volcano, visitors should check local conditions and any advisory notices before traveling. Tonga may have specific regulations for accessing volcanic areas. Guided tours are often the safest and most informative way to experience a volcano.
