Volcanic Ash in Guam, May 23 to 25, 2003

Anatahan began erupting suddenly from its east crater at about 1800 on May 10. Within hours of the eruption's onset, a towering column of volcanic ash and gas rose to more than 33,000 feet above sea level, and the prevailing wind blew the ash westward. This was the first eruption in recorded history on the island. Anatahan Volcano is a small volcanic island located 80 miles north of Saipan Island and 200 miles north of Guam. The island is about 5.6 miles long and 3 km 2 miles wide. Anatahan is a stratovolcano that contains the largest known caldera in the Northern Mariana Islands. The island has been uninhabited since 1990, when an earthquake swam forced the evacuation of the island residents.The eruption buried the island's village in about a foot and a half layer of ash. Analysis of the earlier earthquake records shows that the explosive activity was preceded by many earthquakes starting 12 hours before the eruption began on the 10th. On May 23 and 24, Typhoon Chan-hom,passing 450 miles east of the Mariana Islands, shifted the prevailing east winds to the south, blowing the eruption column toward Saipan and Guam. Light ash fall resulted in flight cancellations at the Saipan and Guam international airports. Residents of Guam and Saipan reported a rotten egg smell associated with the ash fall. The sulfur dioxide gas emitted by the volcano combines with atmospheric moisture produces volcanic smog also know as VOG. The ash plume prompted Continental Airlines to cancel six of its scheduled flights from Saipan.