Images of the Day: Tonga Islands Grow Larger

New Landmass Formed by Hunga Tonga-Hunga Ha’apai Eruption

Submarine Eruption in the Tonga Islands

Image acquired March 26, 2009

Image acquired November 14, 2006

In mid-March 2009, a plume of ash and gas burst out of the ocean as an undersea volcano began to erupt in the South Pacific nation of Tonga. Small sections of the rim of the large undersea volcano had been above water, forming the islands of Hunga Tonga and Hunga Ha’apai. The eruption occurred at two vents, one submerged and the other on Hunga Ha’apai. The eruption pumped out enough rock and ash that by March 25, when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured the top image, the submerged vent was surrounded by new land.

The new land is the dark mass south of Hunga Ha’apai. It had not been present when ASTER acquired the lower image on November 14, 2006. In the March 25 image, clouds cover the space between the new land and Hunga Ha’apai, but news reports indicate that the new land connects Hunga Ha’apai with the underwater vent, essentially enlarging the small island. The vent itself is the nearly perfect circular hole near the southern edge of the new land.

The image reveals some of the other impacts of the eruption. The ocean around the erupting volcano is bright blue, likely colored with ash, rock, and other volcanic debris. The eruption also killed or damaged plants on Hunga Ha’apai. In these false-color images, plant-covered land is red. In 2006, Hunga Ha’apai had supported vegetation, but after the eruption, the island was black. Either the plants were buried in ash or dead in the wake of the eruption. According to a visiting reporter, the eruption destroyed plant and birdlife on the island, leaving blackened tree stumps and dead birds and fish.

NASA image created by Jesse Allen, using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Holli Riebeek.Instrument: Terra – ASTER

Related and Possibly Related Links:

• Weekly Volcano Watch: 26 March 2009
• Hunga Ha’apai Volcano Update
• Magnitude 7.9 Quake Strikes Tonga Region
• Weekly Volcano Watch: 19 March 2009
• Rumble III Volcano “blew its top!”
• Tonga’s Metis Shoal may be erupting
• Magnitude 7 Earthquake Hits Kermadec Islands

Tonga’s Metis Shoal may be erupting

Metis Shoal Submarine Volcano May Be Erupting

1. FEWW seismic analysis of Tonga Islands region in south Pacific Ocean (SPO) indicate that Metis Shoal, a submarine volcano located midway between the islands of Kao and Late (about 50 km NNE of Kao), may be about to erupt, or is currently undergoing a period of unrest.

2. Metis Shoal’s last known eruption occurred in 1995, which produced an island with a diameter of about 300 m and a height of 43 m after a solid lava dome was formed above the surface of water in SPO.

3. Since 1851 some 8 episodes of unrest have been recorded. In three, possibly five, of those occasions new islands were created (1858, 1967-68, 1979, 1995).

Metis Shoal

• Country:  Tonga
• Region:  Tonga Islands, SPO
• Volcano Type:  Submarine volcano
• Last Known Eruption:  1995
• Summit Elevation:  43 m asl
• Latitude: 19.18°S   19°11’0″S
• Longitude:  174.87°W   174°52’0″W

4. Metis Shoal, a submarine volcano midway between the islands of Kao and Late, has produced a series of ephemeral islands since the first confirmed activity in the mid-19th century. An island, perhaps not in eruption, was reported in 1781 and subsequently was eroded away. During periods of inactivity following 20th-century eruptions, waves have been observed to break on rocky reefs or sandy banks with depths of 10 m or less. Dacitic tuff cones formed during the first 20th-century eruptions in 1967 and 1979 were soon eroded beneath the sea surface. An 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. [Caption: GVP]

5. Waves break over Metis Shoal on February 19, 1968, more than a month after the end of a submarine eruption that began in December 1967 and produced an ephemeral island. Metis Shoal has produced a series of small islands during eruptions observed since the mid-19th century. Most recently, an eruption in 1995 produced a lava dome that built up to 43 m above sea level. Photo by Charles Lundquist, 1968 (Smithsonian Astrophysical Observatory). Caption: GVP

6. Map of the Tonga Islands, showing the island groups and location of Metis Shoal, which re-emerged as an island in June 1995. Source: GVP

Other Photos of Metis Shoal

7. Metis Shoal, sea level view. Source: MTU

8. Metis shoal, aerial view. Source: MTU

9. Metis Shoal aerial photo dated December 7,  2006. Source: GVP

Related Links:

• Global Volcanism Network Bulletin v. 20, no. 6, June 1995 Eruption builds new island
• Metis Shoal: Index of Monthly Reports (GVP)

• Two Volcanoes Erupt in Japan
• Volcanoes [Links page]
• Earthquake Forecast 2009 : Japan
• A New Era of Intense Volcanic Unrest May Have Begun
• Earthquakes [Links page]

• Climate Change, Earthquakes, Volcanic Eruptions

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