# Why monitor volcanoes of the Commonwealth of Northern Mariana Islands?

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As if to remind us that active volcanoes are in the region, a billowing column of volcanic gases has been spewing from Anatahan Volcano in the Northern Mariana Islands.

Wide view of Anatahan Volcano. May 9, 2006.

(Public domain.)

The Mariana Islands are the southern part of a chain of volcanoes in the western Pacific. Guam, the southernmost island in the chain, is a U.S. territory. North of Guam, the Mariana Islands extend for approximately another 900 km (560 miles). There are 9 volcanic islands and approximately 15 seamounts that form an island arc system. The Volcano Islands, include Iwo Jima and many other volcanoes, extend from there to the Japanese main island.

The volcanoes crop up in this region because of convergence of the Pacific and Philippine plates in this part of the Pacific. Most people are familiar with the area because the deepest point in the world's oceans is in the Mariana trench.

Most of the Mariana Islands are uninhabited, and three of them have a small number of people living on them. Why is it important to monitor these volcanoes? One could argue that all people's lives are invaluable and that we should ensure their safety at any cost. Another urgent concern is that ash produced by Mariana volcanoes poses a significant hazard to airborne travelers.

Airborne volcanic ash, at jet-cruising altitudes, is the only natural phenomenon known to cause total loss of thrust/power in all four engines of a jet aircraft. There are nine active volcanoes within the Commonwealth of the Northern Mariana Islands (CNMI) that can pose a significant hazard to air traffic and, thus, to the economy of CNMI.

Within the immediate airspace surrounding the CNMI, there are approximately 25,000 large commercial passenger flights per year and more than 1,000,000 flights of large commercial aircraft that transit from Asia to Australia and New Zealand. Air traffic also can be potentially affected by eruptions in the CNMI that criss-crosses from the U.S. to the Australasia/Oceania region. On average, more than 1,200 passengers and 86,000 pounds of cargo fly in and out of Saipan each day.

On May 15, 1981, Mount Pagan produced an ash column more than 15,800 m (52,000 feet) high. Ash fall was reported on Saipan and Guam the following day. In the past three years, Anatahan has had three or more eruption episodes propelling ash to heights of 15,200 m (50,000 feet) or more and twice as many where ash soared higher than 9,100 m (30,000 feet). Ash from Anatahan has drifted south over Saipan and Guam and more than 1,000 km (620 miles) west over the Philippine Islands. Ash from Mariana volcanoes can have far-reaching effects, impacting a large region.

Commercial flights from Hawai'i to the Philippines and Hong Kong, and Japan, Saipan, Guam, Australia, and New Zealand pass over volcanoes of the Northern Mariana Islands. When an explosive eruption from these islands sends volcanic ash and gas high enough to affect aircraft, it is extremely important for pilots already airborne, and airline dispatchers on the ground, to receive immediate notification of the volcanic activity and location of the resulting eruption cloud.

A volcano-monitoring system is imperative for providing early warning of future eruptions. Accurate forecasts of volcanic activity are essential to helping pilots avoid flying through ash clouds. The U.S. Geological Survey's Volcano Hazards Team has established a strong record of mitigating the volcanic threat to aviation by providing eruption forecasts and notifications to the aviation community, other federal agencies, and the global Volcanic Ash Advisory Center system.

Far-flung islands in the Pacific Ocean potentially could have far-reaching impacts. We have instrumented Anatahan Volcano and have 24-hour duty to spot volcanic activity that threatens aircraft. As funding becomes available, we will instrument more of the volcanoes. In order to minimize risk, the U.S. Geological Survey is working cooperatively with colleagues in the Emergency Management Office to monitor volcanoes in the CNMI and to ensure public safety.

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### Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The number of earthquakes located in the summit area is low (usually less than 10 per day that are large enough to locate). Widening of the summit caldera, indicating inflation, appears to have resumed after pausing earlier in April.

Eruptive activity at Puu Oo continues. On clear nights, glow is visible from several vents within the crater. Lava continues to flow through the PKK lava tube from its source on the flank of Puu Oo to the ocean, with frequent surface flows breaking out of the tube at the 2,300-2,200-ft elevation. In the last week, no active flows were reported on the coastal plain.

Lava is still entering the ocean at East Laeapuki, in Hawaii Volcanoes National Park. The active lava bench continues to grow following the major collapse of November 28 and is now approximately 1,000 m (3,300 ft) long by 315 m (1,000 ft) wide, with a total surface area of 20 ha (49 acres).

Access to the sea cliff near the ocean entry is closed, due to significant hazards. The National Park has reopened the surrounding area, however. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There was one earthquake beneath Hawai`i Island reported felt within the past week. A magnitude-3.4 earthquake occurred at 7:17 a.m. H.s.t. on Friday, June 16, and was located 4 km (3 miles) south of Volcano at a depth of 4 km (2 miles).