TSUNAMI ADVISORY WARNING BULLETIN ISSUED FOR AMERICAN SAMOA DUE TO UNDERWATER TONGA VOLCANO

Courtesy of https://www.tsunami.gov/

TSUNAMI ADVISORY WARNING BULLETIN ISSUED FOR

AMERICAN SAMOA DUE TO UNDERWATER TONGA VOLCANO

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Tonga hit by tsunami after underwater volcano eruption

Six underwater #volcanoes discovered near #Sicily, #Mediterranean Sea

Scientists have discovered a series of previously unknown volcanoes just off the coast of SW Sicily, Italy. The three northern volcanoes show a tuff cone-like morphology while the three most southern edifices have a truncated-conical shape. Ages of all newly discovered volcanoes are Late Quaternary. Only the northernmost volcano shows indications of a post-Last Glacial Maximum magmatic reactivation.

The Graham and Terrible banks, located about 35 km (21 miles) from the south-western coast of Sicily, host a large number of volcanic constructs, the most famous being the ephemeral Ferdinandea Island, authors said in the abstract of the new study, published recently in Elsevier’s Marine Geology.

These volcanoes occur along two N-S trending strike-slip lineaments that constitute the lithospheric-scale Capo Granitola-Sciacca, Fault Zone.

In the study, the researches presented recently acquired swath bathymetric data and magnetic measurements, in conjunction with high-resolution seismic profiles, which reveal the presence of another six volcanic edifices located very close to the Sicilian coasts, one of which is only 7 km (4.3 miles) away.

3 of these volcanic constructs have been previously identified only on the basis of available seismic profiles, but their morphology and their volcanic nature had so far not been documented. 2 edifices to the north show a possible tuff cone/ring-like morphology modified by crater breaching, while the three southernmost volcanoes have a truncated-conical shape.

The northwestern-most volcano (here called Actea) shows a more complex morphology, probably representing the remnants of a previous crater rim.

Seismic data analysis suggests that the six volcanic edifices were generated during a pre-Last Glacial Maximum (ca. 20 000 B.P.) magmatic phase associated with a tectonic event.

Only the Actea volcano shows indications of magmatic reactivation, possibly between the LGM and the initial post-LGM transgressive phase. This reactivation is evident by the emplacement of a prominent young lava flow.

The discovery of submerged volcanoes so close to the populated coast of Sicily demonstrates that there are large submerged areas near the littoral that are still little known and studied, and underlines how crucial it is to analyze the issue of volcanic risk for densely inhabited coastal areas like Sicily.

Courtesy of planetxnews.org

https://tinyurl.com/yxg9czek

#Underwater #Volcano Discovered Near #Mayotte

 

Undersea Volcano Called Kick ‘Em Jenny Rumbling off Grenada

An active underwater volcano off Grenada’s northern coast called Kick ’em Jenny was rumbling Thursday and regional disaster authorities were put on alert, though they said it posed no threat of triggering a destructive tsunami.

 

Since its discovery in the 1930s, Kick ’em Jenny has erupted beneath the surface of the Caribbean Sea at least 12 times, most recently in 2001. The volcano, which rises 1,300 meters (4,265 feet) above the seafloor on a steep slope of the Lesser Antilles ridge, hasn’t caused any known deaths or injuries.

 

The Seismic Research Center at the University of the West Indies said seismic activity had increased in the volcano, which sits 8 kilometers (5 miles) north of Grenada. Recreational divers have reported seeing some “degassing” on the seafloor off Grenada’s west coast as gas-rich magma bubbles.

 

Center researchers put the alert level at “orange,” which means an eruption could take place within 24 hours. An eruption would stir up high waves and heat surrounding waters to boiling temperatures. Scientists say the volcano can also shoot hot rocks up through the water column.

 

Under the alert, all boats must stay at least 5 kilometers (3 miles) from the volcano. Kick ’em Jenny poses the greatest threat to mariners since the gases it releases can lower the density of water so significantly vessels can lose buoyancy and sink.

 

Acting Prime Minister Elvin Nimrod said Kick ’em Jenny poses “no significant threat” to Grenada or other coastal communities on nearby islands for now.

 

“There is no need to move people away from coastlines,” he told reporters.

 

People were advised to go about their lives normally. But some were jittery as seismic activity ramped up, knocking out Internet service.

 

“People are just wondering what’s next,” said Kendel Mark, a resident of the outlying island of Carriacou.

 

In a 1939 eruption, Kick ’em Jenny shot a cloud of ash 270 meters (900 feet) above the sea surface. Its eruptions since then have been weaker.

Courtesy of abcnews.go.com

http://goo.gl/vMdAOA

Mount Etna Volcano Eruption On 12th May 2015

Seafloor sensors record possible eruption of underwater Axial Volcano

If a volcano erupts at the bottom of the sea, does anybody see it? If that volcano is Axial Seamount, about 300 miles offshore and 1 mile deep, the answer now is yes.

 

Thanks to a set of high-tech instruments installed last summer by the University of Washington to bring the deep sea online, what appears to be an eruption of Axial Volcano on April 23 was observed in real time by scientists on shore.

 

“It was an astonishing experience to see the changes taking place 300 miles away with no one anywhere nearby, and the data flowed back to land at the speed of light through the fiber-optic cable connected to Pacific City — and from there to here on campus by the Internet in milliseconds,” said John Delaney, a UW professor of oceanography who led the installation of the instruments as part of a larger effort sponsored by the National Science Foundation.

 

Delaney organized a workshop on campus in mid-April at which marine scientists discussed how this high-tech observatory would support their science. Then, just before midnight on April 23 until about noon the next day, the seismic activity went off the charts.

 

The gradually increasing rumblings of the mountain were documented over recent weeks by William Wilcock, a UW marine geophysicist who studies such systems.

 

During last week’s event, the earthquakes increased from hundreds per day to thousands per day, and the center of the volcanic crater dropped by about 6 feet (2 meters) over the course of 12 hours.

 

“The only way that could have happened was to have the magma move from beneath the caldera to some other location,” Delaney said, “which the earthquakes indicate is right along the edge of the caldera on the east side.”

 

The seismic activity was recorded by eight seismometers that measure shaking up to 200 times per second around the caldera and at the base of the 3,000-foot seamount. The height of the caldera was tracked by the bottom pressure tilt instrument, which measures the pressure of the water overhead and then removes the effect of tides and waves to calculate its position.

 

The depth instrument was developed by Bill Chadwick, an oceanographer at Oregon State University and the National Oceanic and Atmospheric Administration who has also been tracking the activity at Axial Volcano and predicted that the volcano would erupt in 2015.

 

The most recent eruptions were in 1998 and 2011. 

 

The volcano is located about 300 miles west of Astoria, Oregon, on the Juan de Fuca Ridge, part of the globe-girdling mid-ocean ridge system — a continuous, 70,000 km (43,500 miles) long submarine volcanic mountain range stretching around the world like the strings on a baseball, and where about 70 percent of the planet’s volcanic activity occurs. The highly energetic Axial Seamount, Delaney said, is viewed by many scientists as being representative of the myriad processes operating continuously along the powerful subsea volcanic chain that is present in every ocean.

 

“This exciting sequence of events documented by the OOI-Cabled Array at Axial Seamount gives us an entirely new view of how our planet works,” said Richard Murray, division director for ocean sciences at the National Science Foundation. “Although the OOI-Cabled Array is not yet fully operational, even with these preliminary observations we can see how the power of innovative instrumentation has the potential to teach us new things about volcanism, earthquakes and other vitally important scientific phenomena.”

 

The full set of instruments in the deep-sea observatory is scheduled to come online this year. A first maintenance cruise leaves from the UW in early July, and will let researchers and students further explore the aftermath of the volcanic activity.

Courtesy of washington.edu

http://tinyurl.com/n9k6hy2