On Saturday May 4th 2013 the Alaska Volcano Observatory detected a series of low-level explosions at Cleveland volcano. Three discrete explosions occurred at 5:00 am, 9:17 am, and 11:44 am Saturday, while subsequent less powerful rumbles on Sunday denoted an ongoing low-level eruption. The sequence of eruptions emitted ash, gas, and steam into local airspace. Cleveland is a 5,676 foot tall conical stratovolcano, a restless volcano prone to rumbles, small explosions, and lava flows. It forms the western half of uninhabited Chuginadak Island in the Pacific Ocean, 940 miles away from Anchorage. Chuginadak is the name of the Native Aleut goddess of fire, who has been said to inhabit the volcano.
The Aleutian Island chain that dots the Pacific ocean southwest of Alaska is home to many volcanoes. The Alaska Volcano Observatory, a joint program of the United States Geological Survey (USGS), the University of Alaska Fairbanks Geophysical Institute (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS), is responsible for monitoring all 90 of Alaska’s active volcanoes.
A volatile volcano
Despite Mount Cleveland’s isolation, monitoring the volatile volcano’s activity is important because Cleveland sits below a major air-thoroughfare for commercial planes travelling between North America and Asia. Ash poses a significant threat to planes: particles of volcanic ash ingested into airline engines can cause engine turbines to stop functioning. Happily the series of small volcanic explosions beginning on May 4th, 2013 expelled an ash plume into the atmosphere at or below 15,000 feet. In contrast, commercial jets flying the trans-Pacific oceanic route usually cruise at an altitude of 35,000 feet. If the ash clouds gain height, the Alaska Volcano Observatory and the National Weather Service will work with the Federal Aviation Administration to safeguard aircraft by diverting routes away from the hazardous area.
The eruption underway poses limited hazards, and so Cleveland volcano is currently under Watch and has an Aviation color code of Orange, signifying minor volcanic-ash emissions. The Alaska Volcano Observatory website states:
“Sudden explosions of blocks and ash are possible with little or no warning. Ash clouds, if produced, could exceed 20,000 feet above sea level. If a large ash-producing event occurs, nearby seismic, infrasound, or volcanic lightning networks should alert AVO staff quickly. However, for some events, a delay of several hours is possible. Cleveland Volcano does not have a local seismic network and is monitored using only distant seismic and infrasound instruments and satellite data. AVO will continue to monitor the volcano and issue additional information as available.”
Notifications for the volcano can be found at the Cleveland volcano page.
Forecasting and managing
When volcanoes spew ash and other atmospheric particulates into the sky, the airborn pollutants can promote cooling by causing less sunlight to successfully pierce the atmosphere. Volcanoes can have a potentially significant impact on global climate. They can also impact human health by altering air quality.
Forecasting eruptions and managing the effects of eruptions is a big job, and the AVO uses a diverse set of monitoring tools to accomplish the tasks. While some volcanoes have local seismic networks in place that notify scientists of earthquakes and surface deformation caused by magma bulging under mountain flanks, Cleveland has no local seismic equipment. A webcam points its way, but cloudy or severe weather often obscures the mount. The scientists make use of distant seismic networks located at other volcanoes to monitor Cleveland’s explosions. They also engage the increasingly comprehensive coverage available from satellites with sensors for visible light as well as thermal cameras that measure the heightened temperatures common to eruptions. At other times, researchers must rely on eyewitness reports from mariners or airplane pilots.
Seismic stations measure shaking in Earth’s crust. Where the Pacific and North