Mount Kelut (also known as Kelud), situated in the east of the island of Java, is one of the most active and hazardous volcanoes in Indonesia. Over the past six centuries the 1730m volcano has erupted at least thirty times and has been responsible for approximately 15,000 fatalities. On 19 May 1919 it was the site of one of the deadliest volcanic eruptions of the twentieth century, killing over 5100 people when water ejected from the crater lake formed lethal lahars that travelled nearly 40 kilometres and destroyed more than 100 villages.

The 1919 eruption is interesting not only for itself but for the response it generated. At the time Java was under Dutch colonial rule, and the Dutch authorities reacted to the disaster both institutionally, by establishing the forerunner of today’s Indonesian volcanological authority, and technologically, by creating a drainage system intended to manage the hazard posed by the crater lake.

The presence of a substantial crater lake has been the main reason why Kelut is a very lahar-prone volcano, but also significant are its deeply eroded flanks and abundance of loose sediment. During the 19 May 1919 eruption 38 million cubic metres of water was expelled from the crater lake, radiating out through the deep drainage channels and accumulating vast quantities of sediment and volcanic material to produce fast-moving lahars that inundated over 30 square kilometres of the surrounding countryside.

Above: map of Kelut, showing the extent of the 1919 lahars. Adapted from Thouret et al, Bull. Volc., 59:7 (1998), fig. 1.

Even before the 1919 catastrophe the colonial authorities recognized the danger Kelut posed and had, in 1905, constructed a dyke intended to protect the nearby city of Blitar. The 1919 lahars, however, overwhelmed this construction. The Dutch response was to abandon the mitigation of lahars and concentrate instead on preventing them developing by enabling the drainage of the crater lake. The work took until 1926 to complete: a system of seven drainage tunnels was constructed, which reduced the volume of the lake by more than 2 million cubic metres, lowering the level by 50 metres. In 1951 the volcano erupted again, but the successful operation of the drainage system meant that little water was present in the crater and no lahars resulted. A second catastrophe had been averted.

The eruption itself, however, deepened the lake and destroyed the drainage tunnels. Only after another deadly eruption in 1966, in which more than 200 people died, was a new deeper tunnel excavated. The most recent large-scale eruption, in 1990, would certainly have been much more destructive to life and property had the crater lake not been largely drained.

Kelut’s most recent period of restlessness occurred in the autumn of 2007 and resulted in evacuations, although there was no large-scale eruptive activity. A lava dome which has grown since the autumn 2007 eruption now fills the crater lake site (see pictures Université Libre de Bruxelles here; h/t to commenter Hawkeye) and has overwhelmed the drainage inlets.

Information
Global Volcanism Program: Kelut - summary information for Kelut (0603-28=).
Kelud Volcano - information and analysis from the Université Libre de Bruxelles, Belgium (ULB). The volcanic lake specialists at ULB are currently collaborating with the Volcanological Survey of Indonesia in monitoring Kelut.
Le volcan Kelut - account of the 1919 eruption and a detailed history, with illustrations, of the various drainage systems built since to drain the crater lake (in French).

On this day twenty-eight years ago, 18 May 1980, Mount St Helens in Washington State, USA, erupted in the most destructive and deadly volcanic eruption in United States history. Fifty-seven people were killed, over one billion dollars of economic damage done, and vast stretches of landscape laid waste by this cataclysmic event.

Resources
Global Volcanism Program: Mount St. Helens - summary information for Mount St Helens (1201-05-)
CVO Menu - Mount St. Helens, Washington - Cascades Volcano Observatory main page for Mount St Helens
CVO Menu - Mount St. Helens - May 18, 1980 - links to a large number of USGS publications and other resources dealing with the eruption
Mount St. Helens National Volcanic Monument - an 110,000-acre area around the volcano, created ‘for research, recreation and education’
Mt St Helens - 25 Years Later - online feature from local Washington newspaper The Daily News, created in 2005 for the 25th anniversary of the eruption

The Alaska Volcano Observatory is currently marking its twentieth anniversary, and a profile of the AVO appears today at AlaskaReport.com. Among other things it explains what a difference technology has made to volcano monitoring and hazard mitigation since the AVO was set up in 1988.

The last two decades have seen the development of satellite sensors that allow people to check for volcano hotspots several times a day, precise GPS receivers that enable scientists to watch volcanoes inflate and deflate, infrasound sensors that record sudden changes in air pressure during explosive eruptions, and the advent of a helpful tool called the Internet.

The article is written by Ned Rozell, a science writer at the University of Alaska Fairbanks Geophysical Institute (one of the partners behind the AVO).

Twenty years of the Alaska Volcano Observatory - AlaskaReport.com, 22 April 2008

Fifty years ago, between September 1957 and October 1958, a dramatic submarine eruption took place on Fayal island in the Azores. Fayal itself is a large stratovolcano with a wide caldera; the eruption took place on the west flank of the volcano, beginning at a point about 1 kilometre west of what was then the westernmost point of the island, and created the volcanic cone of Capelhinos which began as an island and is now a peninsula.

The eruption was one of the most closely-studied in the history of volcanology. It was also highly disruptive for the island’s population: vast amounts of ash were erupted, agriculture was ruined, hundreds of homes destroyed or rendered uninhabitable, and the economy of the island severely damaged. More than 2000 people were evacuated, many to begin new lives in the United States, where a sizeable Portuguese-American population traces its origins to the eruption and the subsequent relief effort today.

The story of Capelinhos is thus not only a scientific story but a profoundly human one as well. The fiftieth anniversary of the eruption is being marked in the Azores and mainland Portugal, and in the United States, with events and publications that reflect all aspects of this historic event.

Information
Smithsonian Institution Global Volcanism Program - summary information for Fayal (1802-01=)
Observatório Vulcanológico e Sismológico da Universidade de Açores - responsible for monitoring volcanism in the Azores (Portuguese)
Vulcão dos Capelinhos - website of the official commemorative commission for the Capelinhos fiftieth anniversary, in English (the Portuguese site is here)

News
Fifty years ago, a volcano changed everything - report from EastBayRI.com on the Capelinhos eruption and the evacuation, which brought many Azoreans to Rhode Island
Erupção do Vulcão dos Capelinhos foi há 50 anos - report on the anniversary from Rádio e Televisão de Portugal (Portuguese)
U.S.-Portugal relationship analyzed at Brown University - report from the U.S. newspaper for the Portuguese community O Jornal on an academic conference inspired by the fiftieth anniversary of Capelinhos (Portuguese language article here)
50th anniversary of the Capelinhos volcano in the Azores - speech by the American ambassador to Portugal, 27 September 2007, to mark the beginning of the 50th anniversary commemorative events

The Alaska Volcano Observatory, established in 1988, is currently celebrating twenty years of volcano monitoring, research and hazard mitigation across Alaska and the North Pacific.

The Alaska Volcano Observatory - 20 Years of Partnership in Support of Public Safety and Volcano Science - USGS Press Release, 3 April 2008
Alaska Volcano Observatory - 20 Years of AVO - anniversary section of the AVO website

On 10 March 1908 members of the British Imperial Antarctic Expedition (also known as the Nimrod Expedition) climbed the active Antarctic volcano Mount Erebus on Ross Island, the first people to make the ascent to the crater rim. The 100th anniversary of this achievement is being marked today at the Mount Erebus Volcano Observatory, which is run by New Mexico Tech at the very un-Antarctic location of Socorro, New Mexico.

Information
Smithsonian Institution Global Volcanism Program - summary information for Mount Erebus
MEVO - Mount Erebus Volcano Observatory
Antarctic Explorers: Ernest Shackleton - detailed biography, includes an account of the Nimrod Expedition

News
Erebus ascent recalled - Stuff.co.nz, 10 March 2008