January 15, 1998
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
Volcanoes Make Headlines!
Kilauea made the headlines once again last week with the threat of a summit eruption and a brief surge in activity that sent lava flows coursing down the pali in Hawaii Volcanoes National Park.
I suspect that every day, somewhere in the world, there's a volcano that makes the local newspapers. Often it's Kilauea. But did you know that there are at least 1,300 active or potentially active subaerial volcanoes in the world? And that in any given year, an average of about fifty erupt?
The Global Volcanism Network (GVN) at the Smithsonian Institution in Washington, D.C. is a clearing house for information on current volcanic activity. GVN receives and compiles thousands of reports from people across the globe, including scientists, residents, hikers, airline pilots, photographers, and a host of other observers of nature.
During the past couple of weeks, for example, preliminary GVN reports indicate that there were at least 16 volcanoes erupting besides Kilauea. Two in Kamchatka (Karymsky, Bezymianny), six in Indonesia or Melanesia (Langila, Rabaul, Ambrym, Manam, Yasur, Semeru), one offshore of New Zealand (Monowai Seamount), one in Antarctica (Mount Erebus), another in Mexico (Popocatepetl), two in Central America (Arenal, Pacaya), one in the West Indies (Montserrat's Soufriere Hills), and, finally, two in Europe (Etna, Stromboli).
Whew! That's a lot of lava! Let's take a closer look a some of these recent eruptions.
Ambrym Volcano in Vanuatu is one of the most active volcanoes in Melanesia. It has erupted almost every year since Captain Cook visited the island in 1774. Ambrym's current activity is much like that of Kilauea---basaltic lava fountains, flows, and vog.
Semeru (Indonesia) and Langila (Melanesia) are also in the midst of long-term eruptions. Semeru has been erupting almost continuously for the last 30 years, and Langila for just under 25. Both volcanoes are belching volcanic ash plumes that rise upwards of 6,100 meters (20,000 feet) on occasion. A few months ago, two climbers were killed on Semeru by hot rocks that were ejected from the crater during a particularly intense ash explosion.
Popocatepetl looms 5,465 m (17,925 feet) above Mexico City, home to nearly nine million people. In December 1994, Popocatepetl reawakened after a fifty-year slumber with an intense explosion of ash. Last summer, an ash column shot up 13,000 meters (42,000 feet) in minutes. Fallout from the column dusted Mexico City and shut down the airport. Recent ash emissions have been relatively modest, but there's a new slug of lava extruding from vents in its summit crater.
For the last two-and-a-half years, Soufriere Hills volcano on the island of Montserrat has been undergoing a "dome-building" eruption, similar in some respects to past eruptions in the U.S. (Cascade Range and Alaska). A massive dome of partially molten rock is forming as lava slowly extrudes and piles up in Soufriere Hills' summit crater. Periods of relatively quiet, but ominous, dome growth are interspersed with explosive episodes that send hurricanes of hot rock and ash racing down the volcano's flanks.
The current eruption of Soufriere Hills has rendered over half of the island uninhabitable, decimated the capital city of Plymouth, caused approximately 6,000 people to leave the island, and claimed 20 lives.
At the other end of the spectrum, there's the benign eruption of Mount Erebus on Ross Island, Antarctica. This ice-covered volcano stands 3794 meters (12,297 feet) tall and has a summit lava lake that has been churning away without consequence for decades.
And let us not forget the new lava flow that's running down the southeast flank of Etna, the molten lava blobs that are being lobbed out of the crater at Arenal, or the ash explosions that erupt every 30 minutes at Karymsky volcano....Well, if you want more, you'll just have to visit GVN's website !
Eruption and Earthquake Update, 15 January
Between 6:20 p.m. and 8:30 p.m. on the 14th, Kilauea's summit experienced rapid inflation centered at a location just east or southeast of Halema`uma`u. Over the next 12 hours the summit settled back to its former state, but lava surged onto the surface from existing vents and tubes near Pu`u `O`o. Three surface flows were formed, the longest an a`a flow that reached the base of Pulama pali, 7.5 km (5 miles) away by about midnight. Lava poured through the tube system from the south shield area near Pu`u `O`o, breaking onto the surface at several places and continuing to the two ocean entries at Waha`ula and Kamokuna. This brief event closely resembles, but was only half as large as, the summit inflation and Pu`u `O`o surge of February 1, 1996.
An earthquake at 7:28 p.m. on January 14 was reported felt by a resident of the National Park. The magnitude 2.2 earthquake was located in the summit of Kilauea Volcano at a depth of 2 km (1.2 mi).
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