More information from NOAA on volcanoes...
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The word volcano comes from the island of Vulcano in the Mediterranean Sea. Long ago people thought this island mountain was the chimney of the blacksmith forge of the Roman God Vulcan. The steam and ash that came out of the vent was a sign that Vulcan was working at his forge making weapons for Jupiter and Mars. In Hawaii and other Polynesian islands, local people once attributed volcanic eruptions to the Goddess Pele. They believed Pele was moving from island to island as she sought to escape her evil sister, Na Maka O Kaha'i, the goddess of the sea. Today, scientists understand that volcanic eruptions are surface reminders of Earth's still hot interior.
The ash cloud formed by the May 18, 1980, eruption at Mount Saint Helens, WA. More images...
Sixty percent of all active volcanoes are found at crustal plate boundaries such as the Pacific Plate. Earth's crust, like the cracked shell of a hard-boiled egg, is broken into a number of "plates". These floating pieces of crust are moving about very slowly on the hotter interior. Where the plates are moving apart or colliding with one another, volcanoes may form. Volcanoes also form oceanic islands in the Pacific Ocean or Mediterranean Sea where "hot spots" occur in the crust and mantle.
Many kinds of volcanic activity can endanger the lives of people and property. Most of the activity involves the explosive ejection or flowage of rock fragments and molten rock. Volcanoes that erupt explosively can send particles as far as 20 miles high and many miles away from the volcano. The volcanic ash from these types of eruptions is a significant hazard to aviation. If an airplane flies into a volcanic cloud, it can lead to engine damage and malfunction and to many other kinds of aircraft damage. Volcanic eruptions near coastlines can generate damaging tsunami waves that can cause death and destruction among coastal communities.
To ensure safe navigation and monitor possible climatic impact, NOAA records global historic volcanic eruptions, tracks volcanic ash eruptions affecting the United States, issues volcanic ash advisories and provides ash cloud forecasts. For more information on volcanoes, visit NOAA's Volcano website
Recent Volcano Observatory Activity Reports from USGS
Semisopochnoi Weekly Update issued Aug 22, 2014 11:26 Volcano Alert Level ADVISORY - Aviation Color Code YELLOW
The number of earthquakes recorded at Smeisopochnoi has decreased significantly over the past two weeks, and is approaching background levels. During the past week, a small number of lower-frequency seismic signals, sometimes associated with volcanic fluids or magma, began to be detected. Nothing unusual was observed in mostly cloudy satellite images over the past week. AVO has received no reports from pilots or mariners of any unusual activity. Details...
Cleveland Weekly Update issued Aug 22, 2014 11:26 Volcano Alert Level ADVISORY - Aviation Color Code YELLOW
Elevated temperatures at the summit were observed this past week during clear satellite views. During clear weather, the recently installed webcam showed an occasional steam plume rising from the summit vent.
Transmission of web-camera images is still in the testing phase, and images will be posted on AVO's public web site soon. Details...
Shishaldin Weekly Update issued Aug 22, 2014 11:26 Volcano Alert Level WATCH - Aviation Color Code ORANGE
Low-level eruptive activity continues at Shishaldin. Elevated surface temperatures at the summit were detected in clear satellite views throughout the week. A steam and gas plume has been occasionally visible in web camera and satellite images. Sound waves consistent with low-level eruptive activity were detected from the direction of Shishaldin on infrasound sensors located in Dillingham and on Akutan Island beginning on August 9 and continuing. No significant activity has been noted in seismic data. Details...
Cascade Range Weekly Update issued Aug 22, 2014 12:00 Volcano Alert Level NORMAL - Aviation Color Code GREEN
Activity Update: All volcanoes in the Cascade Range of Oregon and Washington are at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; and Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.
Recent Observations: Monitoring systems show that activity at Cascade Range volcanoes during the past week has remained at background levels. Details...
Kilauea Daily Update issued Aug 22, 2014 07:06 Volcano Alert Level WATCH - Aviation Color Code ORANGE
Activity Summary: Kīlauea continued to erupt at its summit and within the East Rift Zone, and gas emissions remained elevated. Deflation at the summit slowed to a stop overnight and the lava lake level was 45–50 m below the Overlook crater rim. At the middle East Rift Zone, the June 27th flow advanced to the northeast, partly confined to a large ground crack.
Recent Summit Observations: Deflation at Kīlauea's summit, which started on August 18, slowed through the day yesterday and stopped overnight. The lava lake level stopped falling as well and was 45–50 m below ... Details...
Pagan Weekly Update issued Aug 22, 2014 11:56 Volcano Alert Level ADVISORY - Aviation Color Code YELLOW
Low-level unrest continued at Pagan Volcano throughout the past week. A steam and gas plume was visible in web camera earlier in the week. For the latter half of the week, seismic and web-camera data streams have not been transmitting. Nothing unusual was observed in mostly cloudy satellite images during the week.
Volcanic gas from Pagan may be noticed downwind of the volcano as a distinctive sulfurous odor. Additional information about volcanic gas and vog can be found on the web at this address: http://hvo.wr.usgs.gov/hazards/FAQ_SO2-Vog-Ash/main.html
Access to the island may be ... Details...
Semisopochnoi Daily Update issued Aug 21, 2014 11:58 Volcano Alert Level ADVISORY - Aviation Color Code YELLOW
Earthquakes continue to be recorded at Semisopochnoi, including a few, small, lower frequency events that have occurred over the past few days. Nothing unusual was observed in cloudy satellite images. AVO has received no reports from pilots or mariners of any unusual activity. Details...
Cleveland Daily Update issued Aug 21, 2014 11:58 Volcano Alert Level ADVISORY - Aviation Color Code YELLOW
Nothing observed in mostly cloudy web camera and satellite images over the past day. Details...
Shishaldin Daily Update issued Aug 21, 2014 11:58 Volcano Alert Level WATCH - Aviation Color Code ORANGE
Low-level eruptive activity continues at Shishaldin. A steam plume extending about 60 km north of the volcano was observed yesterday in satellite images, and elevated surface temperatures at the summit were detected in satellite views overnight. Sound waves from the direction of Shishaldin continue to be detected on an infrasound array located on Akutan Island. Details...
Kilauea Daily Update issued Aug 21, 2014 08:53 Volcano Alert Level WATCH - Aviation Color Code ORANGE
Activity Summary: Kīlauea continued to erupt at its summit and within the East Rift Zone, and gas emissions remained elevated. The summit deflated gradually and the lava lake level fell slightly. At the middle East Rift Zone, the June 27th flow advanced through forest northeast and east-northeast of the vent.
Recent Summit Observations: Gradual deflation at Kīlauea's summit, which started on August 18, continued over the past day. The lava lake level dropped as well and was around 45 m below the Overlook crater rim this morning. A swarm of long-period earthquakes ~8 ... Details...
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