# Volcano Watch — Surprise Eruption in Chile Sparks Interest in National Volcano Early Warning System

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During the evening of April 30, in a distant volcanic region in the southern Andes about 1050 km (650 miles) south of Santiago, Chile, strong ground shaking was the first sign that something was awry. Thousands of people felt an increasing number of strong earthquakes that just wouldn't quit.

Typical eruption column of Chaitén Volcano, Chile, on May 26, 2008, between stronger explosive activity. The circular caldera rim is 3 km (1.9 miles) in diameter, which was formed about 9,400 years ago. A lava dome that erupted sometime later is the knobby feature between the billowing ash and rim on the left. A new lava dome is growing in the caldera but it is out of view behind eruption column. U.S. Geological Survey photograph by J.N. Marso.

(Public domain.)

Without nearby seismic monitoring networks, no one really knew where the earthquakes were located, whether they were volcanic in origin, or how long smaller earthquakes might have preceded the "felt" events. The nearest seismometer was located more than 200 km (125 miles) away.

That would be like trying to monitor earthquakes on the Big Island with instruments located on Molokai!

The significance of the felt earthquakes became clear only 27 hours later, in the middle of the night, when long-quiet Chaitén Volcano "suddenly" erupted explosively, sending an enormous plume of pumice, ash, and gas 18 km (11 miles) high for 6 hours. Ash was blown quickly into neighboring Argentina and over the Atlantic Ocean, blanketing vast areas with pumice and ash.

Before the eruption, Chaitén was considered a low threat to people and economic activities in this remote part of Chile. The volcano's previous eruptions occurred about 9,400 years ago and formed a caldera about 3 km (2 miles) in diameter. These were followed sometime later by extrusion of a lava dome.

After the initial eruption on May 1, a continuous ash column was punctuated by larger explosive events on May 6 and 8, and a lava dome began erupting on May 9. The dome is still growing today, accompanied by a steady column of ash and gas (see photograph).

The eruption has greatly affected the lives of people in the area and in neighboring Argentina. All residents of the coastal town of Chaitén (population 4,700), located 10 km (6 miles) from the volcano, were evacuated by May 6. Chaitén is the gateway for Chilean tourism in Patagonia and a center of commercial salmon aquaculture. Within two weeks of the eruption's onset, a thick accumulation of ash and heavy rainfall led to lahars (volcanic mudflows) and sediment-laden floods that inundated the town and airport.

Other people within 50 km (31 miles) of the volcano were also promptly evacuated by the Chilean government. Most were taken out by boat; the first evacuees were the elderly, pregnant or very young.

Later in May, with people safely out of harm's way and new seismic instruments tracking the volcano's activity, a monumental effort was made to evacuate or rescue hundreds of pets, thousands of livestock, and an estimated 600,000 salmon from a fish farm at the mouth of Rio Chaitén.

Hundreds of airline flights in Chile and Argentina and beyond were canceled because of the frequent, high ash clouds and ash fall on the region's airports. Several jets have encountered ash from the volcano, but none have lost engine power or appear to have experienced serious damage.

A small team of U.S. Geological Survey (USGS) scientists and a cache of monitoring equipment landed in Chile on May 17 to help Chilean scientists install a real-time seismic monitoring system for assessing future hazards and activity. Despite poor weather and intermittent ash fall, a skeletal monitoring system was installed within a week, thanks to the logistical support and determination of Chile's armed forces.

This response was supported by the Volcano Disaster Assistance Program, a 22-year collaborative project between the U.S. Agency for International Development (USAID) Office of U.S. Foreign Disaster Assistance and the USGS.

The Chaitén experience is leading the Chilean government to plan a National Volcano Early Warning System (NVEWS) modeled after a 2005 USGS report proposing a monitoring strategy for U.S. volcanoes. The strategy ranks hazards posed by volcanoes into threat levels, assesses the monitoring gaps, and recommends upgrading the monitoring capability according to the threat level.

The report showed that only 8 of the 103 volcanoes in the U.S. classified as moderate, high, or very high threat have adequate monitoring. Fifty-seven of these volcanoes are unmonitored or severely under-monitored.

Chile has more than 120 potentially active volcanoes but only seven are monitored by one volcano observatory.

Both countries have a long way to go to confidently provide early warning for future eruptions of volcanoes like Chaitén.

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### Volcano Activity Update

Kīlauea Volcano continues to be active. A vent in Halemaumau 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 Hawaii Volcanoes National Park, during kona wind periods.

Puu Oo 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 Hawaii coast. Kona winds blow these emissions into communities to the north, such as Mountain View, Volcano and Hilo. The new gas vent observed on May 23 inside Puu Oo remains active, and aerial images captured by thermal camera suggest that the vent may have enlarged slightly since last week. Thermal images peering through fume also show what looks like a small pad of new lava at the bottom of a deep pit on the floor of Puu Oo crater.

The amount of lava erupting from fissure D of the July 21, 2007 eruption has increased fairly significantly over the past week. This excess lava is feeding several breakouts along the 2007 Thanksgiving Eve Breakout (TEB) tube system above the pali. Most of this lava is staying close to the breakout points resulting in an apparent resumption of rootless shield construction over the tube. This is similar to what was seen early in the year. Some active lava is reaching into the northeast corner of the Royal Gardens subdivision.

Lava also continues to flow through what remains of Royal Gardens and across the coastal plain to the ocean in a well-established lava tube active now for several months. The Waikupanaha ocean entry, where lava meets the water, was active throughout the last week, often showing off with small explosions and a vigorous plume. A small delta collapse, which likely occurred very early Wednesday morning, took a deep bite out of the front of the Waikupanaha delta.

Be aware that lava deltas could collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions, as have been seen lately. 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 the County of Hawaii Civil Defense Website or call 961-8093 for viewing hours.

Mauna Loa is not erupting. No earthquakes were located beneath the summit. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.

Four earthquakes beneath Hawaii Island were reported felt within the past week. A magnitude-3.6 earthquake occurred at 6:34 a.m., H.s.t., on Sunday, June 29, 2008, and was located 34 km (21 miles) southt of Ulupalakua, Maui at a depth of 22 km (14 miles). A magnitude-2.9 earthquake occurred at 5:48 p.m. on that same day and was located 11 km (7 miles) northwest of Kailua at a depth of 11 km (7 miles). A magnitude-2.6 earthquake occurred at 8:41 a.m. on Monday, June 30, and was located 12 km (7 miles) northwest of Pahala at a depth of 9 km (5 miles). A magnitude-2.5 earthquake occurred at 1:54 p.m. on Tuesday, July 1, and was located 2 km (1 mile) northeast of Puulena Crater, Puna, at a depth of 2 km (1 mile).

Visit our Website 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