Geologic Background:
Metis Shoal, a submarine volcano midway between
the islands of Kao and Late, has produced a series of
ephemeral islands observed since the mid-19th century.
Its eruption in 1995 produced an island with a diameter
of 280 m and a height of 43 m following growth of a lava
dome above the surface. Dacitic tuff cones formed during
the first 20th-century eruptions in 1967 and 1979 were
soon eroded beneath the sea surface.
Historic Activity:
- Eight previous episodes of activity are known since
1851; new islands were created on at least three (1858,
1967, and 1979), and possibly five, of those occasions.
- The 1967-68 island appeared around 11 December 1967,
and had submerged again by 19 February 1968.
- In 1979, large pumice rafts were seen in May between
Tonga and Fiji. Metis was seen in strong eruption in June
with ash emission in July, and fumarolic activity in
August. The island, named Late Iki by the Tongan
government disappeared in Octobor 1979.
Recent Activity:
- On June 6, 1995 Metis Shoal was reported to be
erupting and was seen by a passing ship on June 9. An
island breached the surface about June 12, but the growth
of a lava dome above sea level was first observed on June
14. The dome was estimated to be 30 m high with a
diameter of 150-180 m. The volume of the lava dome was
estimated at about 1,000,000 cubic meters. By June 20 the
lava dome was 240 x 280 m in size and about 54 m above
sea level. On June 25 the elliptical dome, 300 x 250 m,
elongate NNE, and about 50 m high had stopped
growing.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 4, No. 5 to V. 4, No.
12)
- Global Volcanism Network (V. 20, No. 6).
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