When I was posting a few weeks ago about volcano observatories, focusing on US observatories because of HVO's 100th anniversary, I pondered what to do about the northern Mariana Islands. The Commonwealth of the Northern Mariana Islands (CNMI) are a protectorate of the United States and as such, the volcanoes in this active arc in the Pacific Ocean are under the watch of the USGS. However, they don't really fall under any specific observatory (see update below), but rather the lonely "USGS Northern Marianas Duty Scientist". This nameless individual provides weekly (or more) reports when something is rumbling in the Northern Mariana Islands, mostly for the benefit of people living on the islands and any air traffic in the region. The population of the CNMI is fairly low, ~53,000 people, and dispersed across many islands, so the volcanoes are not a threat to any large population center, but they are definitely active and potentially dangerous. One of the more active volcanoes in the Mariana Islands chain is Pagan on the island of the same name (see above). The island itself is actually two volcanoes - North and South Pagan - both of which were built inside calderas. Most of the recent activity has been from North Pagan, although eruptions from South Pagan occurred in 1864 (and possibly in 1929). Although most of the activity from North Pagan is fairly minor - VEI 1-2 explosive events - 1981 did see an VEI 4 eruption that produced explosions and lava flows. This means that keeping an eye on the current activity on Pagan is well worth our time. The latest report from Pagan notes a ~3 km/10,000 foot plume from the volcano that is mostly steam, although various reports suggest there might be small amounts of ash mixed in. As mentioned in the report, Pagan has no permanent ground monitoring, so all the reports are from either remote sensing via satellite or pilot's reports as they pass near the island. Due to these plumes, Pagan has been on Yellow Alert status (Advisory) since October 2011. The largest eruption in the recent past in the Northern Mariana Islands was from Anatahan in 2003, the first historic eruption of that volcano, showing that even the quieter volcanoes need to be watched. UPDATE 7:00 PM 2/6/2012 - I received an email from Wendy Stovall, the USGS VHP webmaster with some clarifications regarding volcano monitoring in the Northern Mariana Islands: The CNMI volcano monitoring falls under the responsibility of the Alaska Volcano Observatory Scientist-in-Charge. The "USGS Northern Marianas Duty Scientist" is position that rotates weekly among USGS volcano observatory staff in Alaska and Hawaii. The USGS, working with Southern Methodist University and the CNMI Emergency Management Office, maintains telemetered seismic sensors on the southernmost volcanoes Anatahan and Sarigan, and infrasound arrays to detect explosive activity of the other, non-seismically monitored CNMI volcanoes including Pagan. Data are telemetered to the CNMI Emergency Management Office in Saipan and then relayed via the internet to USGS scientists in Alaska and Hawaii to check for signs of activity. Satellite monitoring of the volcanoes is undertaken by both USGS monitoring for signs of activity and NOAA scientists looking for ash clouds. So, there you have it - the CNMI falls under AVO's jurisdiction. Thanks to Wendy for that clarification!
Image: Pagan Island in 2007 / Courtesy of the NASA Earth Observatory
