The U.S. Geological Survey said today that monitoring gaps exist for volcanoes in Hawai'i, Alaska, California, Washington, Oregon, Wyoming and the Northern Mariana Islands that could pose a hazard both on the ground and to aviation.

The report reviews the hazard of 169 volcanoes in the U.S. and its territories and calls for a 24-hour, seven-day Volcano Watch Office and increased monitoring at many of the peaks.

"We cannot afford to wait until a hazardous volcano begins to erupt before deploying a modern monitoring effort. The consequences put property and people at risk including volcano scientists on site and pilots and passengers in the air," said Survey Director Chip Groat.

"It forces citizens, scientists, civil and aviation authorities, and businesses into playing catch up with a dangerous volcano, a risky game indeed," he said.

Monitoring volcanoes in advance of problems is essential to help develop emergency response plans to keep communities safe, he said.

The study said three groups of volcanoes are the highest priority for study:

— The volcanoes erupting now — Kilauea on the Big Island, Mount St. Helens in Washington State, Anatahan in the Northern Mariana Islands — and the volcanoes that are showing periods of significant unrest, the Big Island's Mauna Loa and Mount Spurr in Alaska.

— The 13 very high threat volcanoes with inadequate monitoring. These include nine volcanoes in the Cascade Range — Rainier, Hood, Shasta, South Sister, Lassen, Crater Lake, Baker, Glacier Peak and Newberry. Also, four Alaskan volcanoes, Redoubt, Makushin, Akutan and Augustine. The agency noted that while Cascade volcanoes do not erupt frequently, they threaten major populations and developments.

— Nineteen volcanoes in Alaska and the Mariana Islands that pose high risks to aviation combined with no real-time ground-based monitoring to detect precursory unrest or the onset of an eruption.

"We nearly lost a fully loaded Boeing 747 to volcanic ash cloud in Alaska in 1989," Capt. Ed Miller of the Air Line Pilots Association said in a statement.

Flying into a cloud of volcanic ash can cause jet engines to fail. Many flights every day pass over volcanic areas.

In addition to the top priorities, the report said 21 under-monitored volcanoes in Hawai'i, Washington, Oregon, California, Alaska, the Marianas and Wyoming are also important targets for monitoring.