#bogoslof

[oenothera5]

“Bogoslof Island from the northwest. Alaska, 1895.”

Purington collection

USGS Denver Library Photographic Collection Library ID: pcw00066

[earthstory]

Submarine Volcano No More?

Bogoslof, located in the Bering Sea, is a submarine volcano…at least for now. Most of the mountain, including the erupting vent, is underwater with just a small island of land above sea level. We posted a few weeks ago (http://bit.ly/2khoF4O) about how the eruptions, which started in December, are significantly altering the shape of this remote Aleutian Island.

A satellite photo taken on January 18 during an eruptive event shows that the plume, which rose to an altitude of 9.4 km (31,000 ft) at least, is two distinct colors: white and gray/brown. The white part is mostly steam and water vapor; the top part is full of ash. It’s common for submarine eruptions to have mostly water vapor and steam because the water traps much of the ash. Bogoslof is a shallow submarine volcano and some ash has been observed in the plumes, but this is the first time it’s been such a significant amount, leading scientist to speculate that the vent may have broken through the surface of the water. Additionally, thermal data is also showing temperatures high enough to suggest lava might be above sea level. There’s no direct evidence yet that the vent has breached the surface, so a verdict has not been reached.

While scientists can’t currently get close to Bogoslof and there’s no equipment on the island, they are still able to monitor the eruption using seismic data, infrasound (low-frequency sound), volcanic lightning, satellite data, and pilot observations. The island itself is uninhabited but the eruption could become an aviation hazard.

RE

Photo Credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response Captions by Kathryn Hansen

References: http://earthobservatory.nasa.gov/IOTD/view.php?id=89476 http://go.nasa.gov/2kJE0It https://volcano.si.edu/volcano.cfm?vn=311300

[wigmund]

From NASA Earth Observatory Image of the Day; January 20, 2017:

Ash Cloud Tells a Story of a Volcano Rising

About halfway down the Aleutian Island chain, tiny Bogoslof Island rises from the Bering Sea. Nobody lives there; the larger Unalaska and Umnak islands to the south have proven more favorable for human settlement. But when Bogoslof erupts, scientists and aircraft pilots take note.

“Bogoslof is just so off the grid, so to speak,” said Erik Klemetti, a volcanologist at Denison University and author of the Eruptions blog at Wired magazine. “However, it ends up being important to know what it’s doing for the sake of flights over the Aleutians.”

Because the Alaskan island is so remote, scientists monitor the eruptions from a distance by satellite and seismologic data. At 11:35 a.m. local time (22:35 Universal Time) on January 18, 2017, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image of a plume rising from the volcano.

Much of the volcano is under water; the tallest parts reach about 150 meters (500 feet) above sea level and span just a few pixels in this image. “Submarine eruptions in the Aleutian arc are rare,” said Chris Waythomas, a geophysicist at the Alaska Volcano Observatory (AVO). “This is the first submarine eruption AVO has been able to monitor with a combination of instruments and techniques—seismic, infrasound, satellite, lightning—so it’s definitely something new for us.”

Note how the plume appears to be two colors. The lower part is white and composed primarily of steam and water vapor. Because the vent has been under water for most of the eruption, its plume contains more water vapor than a plume from a typical terrestrial volcano in Alaska. The upper part of the plume is dark gray-brown and rich in ash. According to Waythomas, “this is the first significant ash-rich volcanic cloud observed during the Bogoslof eruption.”

The presence of an ash cloud has led scientists to speculate that the vent might now be above sea level, but there is no direct evidence. Still, the island is changing shape with every large eruptive event. Thermal data (not pictured) show high temperatures for the first time, a clue that lava might be finding its way to the surface above the water line.

References and Related Reading:

Alaska Volcano Observatory (2017, January 19) Bogoslof. Accessed January 19, 2017.

Klemetti, E. (2017, January 5) Explosive Eruptions Continue to Rock Alaska's Bogoslof Volcano. Wired Science: Eruptions Blog. Accessed January 19, 2017.

NASA Earth Observatory (2017, January 3) Bogoslof Kicks Off 2017 with a Bang.

Smithsonian Institution, Global Volcanism Program (2017, January 17) Bogoslof. Accessed January 19, 2017.

NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Caption by Kathryn Hansen. Instrument(s): Terra - MODIS

[earthstory]

Before and After

In the latter part of December, a small volcanic island off the coast of Alaska suddenly awakened. That island represents a volcano called Bogoslof – a volcano in the Aleutian Island chain that rises slightly above the waters of the Pacific. Prior to December, its last known eruption was in 1992, so the picture at the left represents basically how this small hunk of rock looked in early December.

The Alaska Volcano Observatory released the second photo this week. Although several features (marked by numbers) are clearly visible, after the series of ongoing explosive eruptions several major changes have happened in the shape of the island, with the expansion most likely representing growth of the volcano through new lava flows or deposition of tephra.

The actual center of the eruption is a crater at the center of the semicircular island. The activity is ongoing, and at the time of this photo the darker water likely represents a mixture of ocean water and volcanic tephra produced by the most recent volcanic output.

The Aleutian Islands lie above a subduction zone where the Pacific Plate sinks into the mantle. In the process the downgoing plate gives off water that reduces the melting point of mantle rocks, eventually producing a chain of volcanoes above it called a volcanic arc. The entire Alaskan Peninsula, the Aleutian Islands, and the Kamchatka Peninsula are all made of volcanic rocks produced by this process.

-JBB

Image credits: AVO http://www.avo.alaska.edu/images/image.php?id=103801 http://www.avo.alaska.edu/images/image.php?id=14114

More on the eruptions: https://www.avo.alaska.edu/activity/Bogoslof.php http://bit.ly/2hpxPrY

[yedi24haber]

Alaska'da Bogoslof Yanardağı'nda patlama

ANCHORAGE ABD’nin Alaska eyaletindeki Bogoslof Yanardağı’nda patlama meydana geldi. Alaska Yanardağ Gözlemevi, eyaletin güneybatısındaki Bogoslof Yanardağı’nın yaklaşık 11 kilometre yüksekliğe kül ve gaz püskürttüğünü açıkladı. Aralık ayından bu yana faaliyette olan yanardağdaki patlamanın 16 dakika sürdüğü belirtildi. Patlamanın ardından Havacılık Uyarı Kodu, en üst düzey olan kırmızıya…

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[uafgina]

“Too Many Lights, Too Many Sources”  ...or...  “Who Put the Bogus in Bogoslof?”

As described in this blog post, https://uafgina.tumblr.com/post/155398902124/volcanoes-aurora-and-clouds-oh-my, during hours of darkness, the Day Night Band detects visible light from a number of sources including reflected moonlight, the northern lights, city lights, ships, and even volcanoes.  

Satellite imagery, and not just the Day Night Band, has been used before to identify volcanoes.  For example, here’s a blog post from the University of Wisconsin showing imagery capturing the eruption of Pavlof Volcano in 2014. http://cimss.ssec.wisc.edu/goes/blog/archives/17179

So one might ask, is it possible to see a bright spot from Bogoslof Volcano in Day Night Band imagery?  It turns out this is unlikely.  Dave Schneider of the USGS’ Alaska Volcano Observatory mentions that the business end of Bogoslof Volcano, its “vent,” is under water and is thus not able to shine particularly brightly from the point of view of a weather satellite.  But wait, then what’s that bright spot in the Day Night Band imagery if it is not a volcano?  It turns out this is actually the town of Unalaska.  As shown in the map below, Bogoslof is about 35 miles northwest of Unalaska Island, and if you’re not careful, the lights of the small town of Unalaska could be mistaken for the lights of a volcano’s vent…and that is exactly the error in the previous blog post.  

Just this very morning Bogoslof got out of bed in a bad mood, perhaps upset about recent inaccuracies in this blog, and unleashed an explosive eruption sending a volcanic cloud up to 30,000 ft.  For the latest information on developments at Bogoslof, please consult the Alaska Volcano Observatory’s web site https://www.avo.alaska.edu/activity/Bogoslof.php

Also, a general description of Bogoslof is available at this link http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Bogoslof

[lovingwonderlanddetective-blog1]

Alaska's Bogoslof Volcano Unexpectedly Erupts, Sparks Aviation Alert - Tech Times

Alaska’s Bogoslof Volcano Unexpectedly Erupts, Sparks Aviation Alert – Tech Times

[ad_1] A sudden eruption of an isolated volcano in Alaska has led to a series of warnings and alerts in the region. Although the event seems to be a rather isolated one, having not caused any casualties or damage, the area continues to be closely monitored to avoid any problems a new eruption might create. On Dec. 20, several airplane pilots reported an eruption on the small island called…

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