Formation of the caldera at the site of the Kuwae volcano after its cataclysmic eruption in 1450.
It is in this caldera that the Karua volcano is formed.
The eruption of the Kuwae at the end of the year 1452 or the beginning of 1453 undoubtedly surpassed that of the Tambora in quantity of sulphurous gas sent into the atmosphere. The climatic consequences of the eruption were significant for several years.
The analysis of numerous samples of ice from the northern and southern hemispheres allowed us to date this cataclysmic eruption.
(Chaochao Gao, Alan Robock, Stephen Self, Jeffrey B. Witter, JP Steffenson, Henrik Brink Clausen, Marie-Louise Siggaard-Andersen, Sigfus Johnsen, Paul A. Mayewski, Caspar Ammann (27 juin 2006).)
Kuwae has erupted at least 12 times since 1452 with the most recent eruption in 1974. Eruptions were reported in 1977, 1979 and 1980 but not confirmed. Most of these eruptions were weak to moderate (VE1 = 0-2). The eruption of 1897-1901 built an island 1 km long and 15 m high.
The island collapsed within six months. The eruptions of 1948-1949 also built a cone of 1.6 km in diameter and 100 m in height. It was also eroded in one year.
Visit to the island of Karua, which emerged in February 1971. © National Geographic Society, New Hebrides
Underwater photo. Rosaries of gas bubbles emitted from the summit area of Karua. © IRD/ G. Bargibant.
The Tongoa and Epi Islands were once part of a larger island called Kuwae.
The local oral tradition tells of a cataclysmic eruption that destroyed this island, leaving the two small islands of Epi and Tongoa.
Monzier (1994) describes an oval caldera of 12 x 6 km formed during the eruption. It dates the event in 1420-1430. The collapse associated with caldera formation could have reached 1100 m. Monzier and his team estimated 32 to 39 km3 of magma ejected, making the Kuwae eruption one of the largest in the last 10,000 years and comparable to that of Santorin and Tombora.
The interpretation of volcanic deposits on Tongoa and Epi (Robin and Col. 1994) suggested that the caldera is formed in three stages:
- Moderate hydromagmatic and magmatic activity from a central vent over a period of a few months or years.
- The dacitic hydromagmatic eruptions which gradually evolve towards a magmatic eruption and the establishment of two major pyroclastic flows and the collapse of the caldera
- Additional eruptions of dacitic pyroclastic fluxes lead to the collapse of the caldera in the northern part.
Department of Geology, Mining and Water Resources, Vanuatu. ORSTOM helps monitor active volcanoes in Vanuatu.
The submarine volcano of Karua settled and developed in the immense caldera (60 km2) that resulted from the cataclysmic eruption of Kuwae around 1450 AD.
This volcano, whose submarine anchorage is located at 400 meters depth, is exposed in 1897 and 1900/1901 followed by new manifestations in 1923 and 1925; It emerged in 1948 (with the construction of an island about 1.5 km in diameter and 100 meters high and disappeared in 1950. It emerged again in 1959 and 1971 and formed an island until 1975.
Between these periods, bubblings and colorations are fairly regularly observed.