Volcano Watch — Lava and Ice Mingle in the South Sandwich Islands

After exploring and claiming land in the South Pacific for Britain during his second of three voyages, Cook set out east from the Pacific in 1775 to the South Atlantic—hugging the southern tip of South America—to locate the fabled Terra Australis, or Southern Continent. He encountered rough seas, bitterly cold weather, and dangerous icebergs. Eventually he discovered a remote chain of small, ice-covered islands with jagged peaks and calving glaciers that he named "Sandwich Land." The chain, now called the South Sandwich Islands, consists of 11 small islands, now named Zavodovski, Visokoi, Leskov, Candlemas, Vindication, Saunders, Montagu, Bristol, Cook, Thule and Bellinghausen. The largest, Montagu, is only about 7 miles wide.

Though penguins and seals thrive on the ice and rock, the islands are utterly inhospitable to people and most vegetation. The well-traveled Cook referred to the South Sandwich Islands as "the most horrible coast in the world," and wrote that the islands were "doomed by nature never once to feel the warmth of the Sun's rays." Cook and his crew returned to Britain, never to find the Southern Continent (Antarctica would be discovered some 45 years later).

These islands are hardly a tropical paradise, so what do they share with Hawai`i, the "north" Sandwich Islands? On one of the earliest visits to the South Sandwich Islands, in 1830, the captain described a "burning mountain" on Visokoi Island, which was an eruption of Mount Hodson volcano. We now know that all the islands in the chain are volcanic in origin and that 8 of the 11 exhibit ongoing volcanic activity. Though the Hawaiian Islands originate from a hot spot in the center of a crustal plate, the South Sandwich Islands are created by subduction of the South American Plate underneath the tiny Sandwich Plate.

Like Hawai`i, the South Sandwich Islands are extremely active volcanically. Mount Michael, on Saunders Island, is thought to host an active lava lake in its summit crater. Mount Belinda, on Montagu Island, was in eruption from 2001 to 2007; a lava flow in September 2005 cut a deep canyon in the mountain's ice cover to reach the sea, producing a huge ocean-entry steam plume and building a lava delta. Elsewhere in the chain are steaming fumarole fields, cinder cones, and fields of jagged `a`a lava.

Also like Hawai`i, the South Sandwich chain features an active submarine vent, Protector Shoal. Just 30 yards below the surface, Protector Shoal erupted in 1962 and created a giant raft of floating pumice, which drifted several thousand miles and reached New Zealand.

Today the South Sandwich Islands are monitored by the British Antarctic Survey, based in Cambridge, England. Unlike people in Hawai`i, volcanologists visiting the South Sandwich Islands can't simply stroll up to the active craters in t-shirts and shorts. The rough seas, calving ice, and steep coastlines make boat landings near-impossible, so any exploration of the islands' interiors requires a hearty ship-based helicopter equipped to land on snow and ice.

Because of these difficulties and the remote location, there have been only three scientific expeditions to the chain. These challenges also make installing and maintaining any volcano-monitoring equipment, such as seismometers and GPS units, impractical. Most of what we know about current volcanic activity in the chain, therefore, has been revealed by analyzing satellite imagery.

In the geopolitical realm, the islands are officially recognized as British territory, though they are claimed by Argentina. A small garrison of Argentine soldiers was briefly established on Thule Island during the 1982 Falkland Islands War, but no fighting occurred in the chain.

Find a globe and try to locate the South Sandwich Islands, southeast of the southern tip of South America. Situated hundreds of miles from civilization, in one of the most inhospitable regions on Earth, it may be no surprise that Argentina and Britain didn't fight over them. Perhaps geologists and penguins are the only ones to appreciate this tiny but fascinating volcanic chain.

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Volcano Activity Update

Kīlauea Volcano continues to be active. A vent in Halema`uma`u Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. Resulting high concentrations of sulfur dioxide in downwind air have closed the south part of Kīlauea caldera and produced occasional air quality alerts in more distant areas, such as Pahala and communities adjacent to Hawai`i Volcanoes National Park, during kona wind periods. There have been several small ash-emission events from the vent, lasting only minutes, in the last week. The vent continues to produce only a dim glow at night.

Pu`u `Ō`ō continues to produce sulfur dioxide at even higher rates than the vent in Halema`uma`u Crater. Trade winds tend to pool these emissions along the West Hawai`i coast, while kona winds blow these emissions into communities to the north, such as Mountain View, Volcano, and Hilo.

Lava continues to erupt from the Thanksgiving Eve Breakout (TEB) vent and flows toward the ocean through a well-established lava tube. Lava breakouts in the Royal Gardens subdivision were interrupted in the past week by a deflation-inflation (DI) event at the summit on October 25-27. This event also caused a short pause in activity at the ocean entry. Activity resumed at the coast on October 28, as did breakouts on the lower part of pali in Royal Gardens.

Be aware that active lava deltas can collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves generated during delta collapse; avoid these beaches. In addition, steam plumes rising from ocean entries are highly acidic and laced with glass particles. Check Civil Defense Web site or call 961-8093 for viewing hours.

Mauna Loa is not erupting. One earthquake was located beneath the summit this past week. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.

Three earthquakes beneath Hawai`i Island were reported felt within the past week. A magnitude-2.6 earthquake occurred at 00:23 a.m., H.s.t., on Saturday, October 25, 2008, and was located 13 km (8 miles) south of Honoka`a at a depth of 34 km (21 miles). A magnitude-2.4 earthquake occurred at 5:31 a.m. on Wednesday, October 29, and was located 25 km (16 miles) southwest of Hawi at a depth of 5 km (3 miles). A magnitude-2.6 earthquake occurred at 6:43 p.m. on the same day and was located 16 km (10 miles) northwest of Kawaihae at a depth of 17 km (10 miles).

Visit our Web site for daily Kīlauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawai`i earthquake information. Kīlauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov. skip past bottom navigational bar