[Vulkanen] The Ring of Fire #8: Het rommelt en borrelt

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Earthquake swarm beneath Loihi volcano Hawaii
The USGS Hawaii Volcano Observatory (HVO) reported increased seismic activity at the submarine Lōʻihi volcano in Hawaii from May 11 to 12, 2020. More than 100 earthquakes were detected, but USGS noted that there is no indication that a submarine eruption has occurred and there are no significant hazards of concern to the Island of Hawaiʻi at this time. Lōʻihi is the youngest Hawaiian volcano located approximately 35 km (21.7 miles) SE of Pahala, at a water depth of approximately 1 km (3 300 feet). Its last major activity was back in 1996.

The swarm, which began around 13:00 UTC (03:00 LT) on May 11, included 79 M2 quakes and 19 M3 and above. It's located beneath the southeast rift zone and southeastern flank at depths of 3 600 to 12 400 m (11 800 to 40 682 feet) below sea level or 1 to 9.8 km (0.6 to 6 miles) below the volcano's surface.

This is a significant increase above long term background rates of fewer than three tremors per day at Loihi, generally measuring M2 below.

The number of quakes peaked at 14 per hour, between 23:00 to 00:00 UTC from May 11 to 12 (13:00 to 14:00 LT on May 11), and then decreased afterward. Earthquake rates have been less than four per hour since early Tuesday, May 12.

Tina Neal with the USGS HVO said her team is monitoring the volcano for activity and that she expects other signs of eruption. Loihi's last major activity was around 24 years ago, during a swarm of more than 4 000 events.

Neal added that given Loihi's location underwater, it is difficult to pinpoint what exactly is happening at the volcano, but she noted that the current increased seismic activity in the area does not pose a threat to Hawaii residents.

"This swarm may represent a brief magmatic intrusion or movement of magmatic fluids within the volcanic edifice," USGS said in a statement issued 22:22 UTC on May 12. "Although the swarm appears to have diminished in intensity if earthquakes become shallower, it could lead to the beginning of a submarine eruption, similar to what occurred in 1996."

If an eruption would occur, USGS said it may cause partial draining of its summit magma chamber, as well as summit collapse. Abrupt changes to the volcano's surface could displace massive volumes of ocean water, which may generate small local tsunami waves.

Earthquakes of magnitude 4 and above could occur if the swarm were to intensify and these may be felt on the Island of Hawaiʻi.

If an eruption or stronger earthquakes occur, very small tsunami waves may affect southeast shores of the Island of Hawaiʻi. Relatively low-energy, steam- and gas-driven explosions can occur at the depth of Lōʻihi, but with limited local effects on the volcano and surrounding ocean water.

There is no direct relationship between the current Lōʻihi swarm and the ongoing increased seismicity observed in Pāhala over the past year, USGS said.

The Lōʻihi swarm is ~35 km (21.7 miles) southeast of Pāhala, at significantly shallower depths. The current Lōʻihi swarm is also unrelated to seismicity observed on the south flank of Kīlauea.

Loi'hi seamount is an active volcano on the seafloor south of Kīlauea Volcano, about 30 km (19 miles) from the shoreline of the Island of Hawaiʻi. The top of the seamount is about 975 m (3 199 feet ) below sea level. The volcano consists of a broad summit area marked by three pit craters and two prominent rift zones extending from the summit about 22 km (13.6 miles) SSE and about 15 km (9.3 miles) NNE. The volcano likely has a shallow magma chamber between 1 to 2.5 km (0.6 to 1.6 miles) deep below the summit.

Earthquake activity has been recorded near Lōʻihi since 1952. Prior Lōʻihi earthquake swarms occurred in 1952, 1971–72, 1975, 1986, 1988, 1990, 1991, 1996, 2005, and 2017, and were characterized by hundreds to thousands of earthquakes occurring over weeks to months with magnitudes ranging up to M4.9.

The largest earthquake detected at Lōʻihi was M5.1 in May of 2005. Many of the 1952 Lōʻihi earthquakes were felt in coastal communities and one of the earthquakes generated a small tsunami that swept inland about 180 m (600 feet) at Kalapana; no damage was reported.

The 1996 Lōʻihi earthquake swarm was one of the most intense earthquake swarms recorded by the HVO monitoring networks and is summarized below.

For the six weeks commencing July 16, 1996, HVO recorded more than 4 000 earthquakes in the LOIHI area. 95 of these earthquakes were between magnitude 4.0 and 4.9, and nearly 400 were stronger than magnitude 3.

Most of the earthquakes occurred during the last half of July during three time periods, each lasting about two to five days and separated by less than one to four days. Subsequent undersea expeditions to the area discovered that the volcano's summit area had collapsed to form a new crater about 550 m (1 800 feet) across and 275 m (900 feet) deep.

Hydrothermal vents were observed in the new crater, and evidence was found of newly erupted lava.

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Eruption at Sangay volcano produces pyroclastic flows, covers several provinces in ash, Ecuador

A strong eruptive event at Ecuador's Sangay volcano on Tuesday, June 9, 2020, produced a thick column of ash that rose up to 7 km (23 000 feet) above sea level. Several provinces were covered in ash, flights delayed and some roads closed.

Ashfall was reported in the provinces of Santa Elena, Guayas, Los Ríos, Chimborazo, and Morona Santiago. The greatest ashfall was reported in the Alausí canton, Chimborazo Province. Residents living in affected regions were urged to wear protective masks.

Intermittent volcanic ash emissions were noted in infrared satellite imagery along with a brilliant hotspot at the summit, extending SE, the Washington VAAC reported at 06:22 UTC.

Remnant volcanic ash extended well W and WSW of the summit to about 300 km (185 miles) downwind, the center reported at 10:43 UTC.

Geophysical Institute of Ecuador (IGEPN) said pyroclastic flows were generated during the event and descended down the southeastern flanks of the volcano. Lava flows remain active, it added.

Yesterday's event is most likely related to the collapse of one or more lava fronts that descended down the southeastern flank of the volcano, the institute added.

Continuous puffs were again reported at 02:05 UTC on June 10, extending up to 85 km (50 miles) from the summit. Models indicated continued movement toward the W

Benjamin Bernard of the IGEPN said the ash spread into Guayas province, with a 'quantity arriving ner Guayaquil.'

Guayaquil airport halted all flights until they cleaned the runway, airport authorities said. The city is located 175 km (110 miles) W of Sangay.

Several roads in the provinces of Los Rios and Chimborazo were reportedly closed due to heavy ashfall.

Residents in affected regions, especially Guayaquil, were asked to wear protective masks to avoid respiratory problems.

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Alerts raised after significant earthquakes under Makushin volcano in Alaska, U.S.

Two earthquakes with magnitudes larger than 4.0 were registered in the vicinity of Makushin volcano, Alaska over the past 12 hours, representing a significant departure from background earthquake activity. The last eruption of this volcano took place in 2005 (VEI 1). A powerful VEI 5 eruption took place in 6100 BCE ± 50 years. Although no large eruptions have occurred in this century, small-to-moderate explosive eruptions have been recorded at Makushin since 1786.

The events -- measuring M4.5 at 21:16 UTC on June 15, M4.1 at 00:34 UTC on June 16, and M3.9 at 02:38 UTC on June 16 -- could be associated with volcanic unrest, the Alaska Volcano Observatory said.

As a result, the Aviation Color Code was raised to Yellow and Volcano Alert Level to Advisory.

"The unrest could result in a future eruption, however, that is not a certainty," AVO said. "Aftershocks continue, as would be expected with earthquakes of this size."

The volcano is monitored with a network of seismic instruments, web camera, GPS, satellite data, and regional infrasound and lightning detection instruments.

The ice-covered, 1800 m (5 905 feet) high Makushin volcano on northern Unalaska Island west of the town of Dutch Harbor is capped by a 2.5 km (1.5 miles) wide caldera. The broad, domical structure of Makushin contrasts with the steep-sided profiles of most other Aleutian stratovolcanoes.

Much of the volcano was formed during the Pleistocene, but the caldera (which formed about 8 000 years ago), Sugarloaf cone on the ENE flank, and a cluster of about a dozen explosion pits and cinder cones at Point Kadin on the WNW flank, are of Holocene age.

A broad band of NE-SW-trending satellitic vents cuts across the volcano. The composite Pakushin cone, with multiple summit craters, lies 8 km (5 miles) to the SW of Makushin.

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Increased seismicity at Pavlof volcano, Alaska

Seismic activity at Pavlof volcano has increased on September 21, 2020, prompting the Alaska Volcano Observatory (AVO) to raise the Aviation Color Code to Yellow and Alert Level to Advisory.

While this does not necessarily mean that an eruption is likely or imminent, past eruptions at Pavlof occurred with little or no warning, AVO stated.

There is currently no observed eruptive activity or emissions in cloudy satellite imagery and web camera views.

"However, the seismic activity represents an increase from background levels and we are thus increasing the Aviation Color Code and Alert Level to YELLOW/ADVISORY," AVO said.

Pavlof is a snow- and ice-covered stratovolcano located on the southwestern end of the Alaska Peninsula about 953 km (592 miles) southwest of Anchorage.

The volcano is about 7 km (4.4 miles) in diameter and has active vents on the north and east sides close to the summit.

Geological summary
The most active volcano of the Aleutian arc, Pavlof is a 2 519-m-high (8 264 feet) Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera.

Pavlof and its twin volcano to the NE, 2 142-m-high (7 027 feet) Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays.

A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera.
Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides.

The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows. (GVP)

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Indonesian volcano Mount Ili Lewotolok erupts, closing airport
No injuries reported but authorities create exclusion zone around the crater

Indonesia’s Mount Ili Lewotolok erupted on Sunday, releasing a column of smoke and ash 2.5 miles (4km) into the sky, triggering a flight warning and the closure of the local airport.

There were no reports of injuries or damage from the eruption in a remote part of the south-east Asian archipelago. But authorities raised the volcano’s alert status to its second-highest level as they warned of possible lava flows.

A 1.2-mile no-go zone around the crater was also expanded to 2.5 miles, while flights were advised to steer clear of the area as volcanic ash rained down on Wunopitu airport in East Nusa Tenggara, which was temporarily closed.

“People are advised to not carry out any activities within a 4km radius from the crater,” Indonesia’s geological agency said.

Indonesia is home to about 130 active volcanoes due to its position on the Ring of Fire, a belt of tectonic plate boundaries circling the Pacific Ocean where frequent seismic activity occurs.

In late 2018, Anak Krakatau, a volcano in the strait between Java and Sumatra islands, erupted and caused an underwater landslide that unleashed a tsunami, killing more than 400 people.

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Heightened volcanic unrest at Mount Ruapehu, New Zealand

The temperature of the Crater Lake (Te Wai ā-moe) at Ruapehu volcano has decreased from 43 to 41 °C (109 - 106 °F) during the past week. The level of volcanic tremor continues to be moderate to strong and a small number of shallow volcanic earthquakes have been recorded. While the crater lake may have stopped heating, volcanic activity at Ruapehu remains elevated -- the Volcanic Alert Level remains at Level 2 and the Aviation Colour Code at Yellow since December 21, 2020.

"Since our last update [on December 21, 2020], Ruapehu’s Crater Lake (Te Wai ā-moe) temperature has decreased slightly. The temperature reached a maximum of 43 °C (109 °F) on December 21 that subsequently declined to about 41 °C (106 °F)," GeoNet's Duty Volcanologist Agnes Mazot said on December 28.

A lake temperature peak of about 40 - 46 °C (104 - 115 °F) is common during these heating-cooling cycles; on at least 7 occasions since 2007, the lake temperature exceeded 40 °C.

Using this lake temperature decrease, it is estimated that the energy input into the lake has decreased from ~400 to ~200 MW (megawatt).

Elevated volcanic tremor is still ongoing along with a few volcanic earthquakes, Mazot added.

The largest of these earthquakes was M2.2 on December 26, located under the volcano. Volcanic earthquakes of this size are uncommon and the combination with elevated tremor and still high lake temperature indicate moderate to heightened volcanic unrest. Because of this, the Volcanic Alert Level remains at Level 2.

"We continue to closely monitor Ruapehu, and this week we will attempt a gas flight to measure volcanic gas emissions. We will also attempt to sample the water at the crater lake for further chemical analyses. Together, these will help us identify processes occurring at depth beneath the volcano."

The Volcanic Alert Level is still at Level 2 which reflects the current level of volcanic activity. Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of volcanic unrest. The Aviation Colour Code remains at Yellow.

The Volcanic Alert Level should not be used to forecast future activity, however, at Volcanic Alert Level 2, eruptions are more likely.

Volcanic Alert Level 2 indicates the primary hazards are those expected during volcanic unrest: steam discharge, volcanic gas, earthquakes, landslides and hydrothermal activity. While Volcanic Alert Level 2 is mostly associated with environmental hazards, eruptions can still occur with little or no warning.

The Department of Conservation (DOC) has closed the summit area of Ruapehu, including a 2 km (1.2 miles) radius from the center of Te Wai ā-moe/Crater Lake.

"Our priority is to protect public safety, so we ask visitors to respect the exclusion zone under Volcano Alert Level 2 [VAL2] for their own safety," Tongariro Operations Manager Connie Norgate said.

Mount Tongariro and the Tongariro Alpine Crossing are not affected by increased volcanic unrest at Mount Ruapehu and remain open.

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Taal volcano alert status raised to Alert Level 2 (increasing unrest), Philippines

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) has raised the alert status of Taal volcano from Alert Level 1 (low level of unrest) to Alert Level 2 (increasing unrest) on March 9, 2021.

Since February 13, 2021, the volcano has been exhibiting increased unrest based on the following monitoring parameters:

Volcanic earthquakes:

The Taal Volcano Network (TVN) recorded a total of 28 volcanic tremor episodes, 4 low-frequency volcanic earthquakes (LFVQs), and 1 hybrid earthquake at shallow depths of less than 1.5 km (0.93 miles) beneath Taal Volcano Island or TVI in 24 hours to midnight UTC, March 9.

Volcanic tremors have increased seismic energy compared to previously recorded episodes and ranged between 3 to 17 minutes in duration.

The total number of volcanic tremor events has risen to 866 since the onset of increased activity on February 13.

In addition to these, a total of 141 LFVQs have occurred at depths within 1 km (0.62 miles) beneath TVI and immediate vicinities. Overall, seismic activity in the past month indicates increased magmatic and hydrothermal activity at shallow depths beneath TVI.

Survey observations in mid-February 2021 recorded a temperature high of 74.6 °C (166 °F) and continuing increase in acidity to pH 1.59 from a pH of 2.79 in January 2020 of the MCL.

Increasing acidity is caused by sustained volcanic gas input into the shallow hydrothermal system that feeds into the lake, signifying degassing of magma intruded at depth during the January 2020 eruption.

Ground deformation:

Integrated real-time ground tilt and continuous GPS and daily Electronic Distance Measurement (EDM) monitoring and Interferometric SAR (InSAR) data analysis indicate ongoing slight deformation of TVI centered on a pressure source on its southeast sector.

Continuous GPS and InSAR data further yield very slow but steady inflation and/or expansion of the Taal region since the end of the 2020 eruption, at very much slower and stabilized rates compared to deformation before and right after the eruption.

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Nicaragua volcano blankets communities in ash

The San Cristobal volcano, the highest in Nicaragua and one of its most active, spewed a cloud of ash Tuesday that blanketed the city of Chinandega and surrounding communities, a local journalist told AFP.

The surprise eruption ejected a column of smoke and ash that was dumped as far as 17 kilometers (10.5 miles) from the volcano's foot, Nicaragua journalist Carol Altamirano said.

"Everything is grey, the crops of rice, sesame, vegetable gardens and fruit trees and the cattle pasture is covered in ash," said Altamirano.

The INETER territorial studies institute predicted less intense action in the coming days and no threat to residents.

The massive ash deposit lasted about 30 minutes, and deep rumbling from the volcano alarmed locals. Cars switched on their headlights as everything went dark.

Farmers in the area covered their water sources and moved their animals to safe places, while in the city people used umbrellas, caps and face masks to shield themselves from the ash rain, said the journalist.

The 1,745-meter (5,725 foot) high San Cristobal is one of seven active volcanoes in the Central American country.

It is located in the Chinandega region, 132 kilometers northwest of the capital Managua.

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Unusual earthquakes highlight central Utah volcanoes

If you drive south through central Utah on Interstate 15 and look west somewhere around Fillmore, you’ll see smooth hills and fields of black rock. The area is, aptly, named the Black Rock Desert. It may not look like much, but you’re looking at some of Utah’s volcanoes.

A pair of earthquake sequences, in September 2018 and April 2019, focused scientists’ attention on the Black Rock Desert. The sequences, which included the main quakes and their aftershocks, were very different from the Magna earthquake that shook the Wasatch Front in 2020 and other Utah earthquakes. The Black Rock sequences were captured by the Utah Regional Seismic Network and by nearby temporary seismic equipment deployment that was monitoring a geothermal well. Earthquakes in the Black Rock Desert are rare and capturing the seismic recordings from these earthquakes provides a glimpse into the volcanic system of the Black Rock Desert that, while not showing any signs of erupting, is still active. A study of the earthquake sequences is published in Geophysical Research Letters.

“The results showed us that we should give more attention to the Black Rock area,” says Maria Mesimeri, a postdoctoral research associate with the University of Utah Seismograph Stations. “We need to improve seismic and volcanic monitoring in this area, so that we are aware of small changes that may occur.”

The earthquake sequences, with main shocks of magnitude 4.0 and 4.1 respectively, were picked up by both the Utah Regional Seismic Network and a dense temporary network of seismometers deployed as part of Utah FORGE, an experimental geothermal project funded by the U.S. Department of Energy and operated by the University of Utah, located about 19 miles south of the Black Rock Desert near Milford, Utah. The temporary network allowed researchers to detect more aftershocks than usual. For example, the regional network detected 19 earthquakes as part of the April 2019 sequence. But the dense temporary network detected an additional 35 quakes. Each additional aftershock provided a bit more information for seismologists studying the sequence.

The Black Rock sequences showed some interesting features that set them apart from the 2020 Magna sequence and other Utah earthquake sequences. While the initial Magna quake occurred at a depth of about six miles below the surface, a typical depth for Utah earthquakes, the Black Rock quakes were much shallower—around 1.5 miles below the surface.

“Because these earthquakes were so shallow,” Mesimeri says, “we could measure surface deformation [due to the quakes] using satellites, which is very unusual for earthquakes this small.”

Also, Mesimeri and her colleagues found, the quakes produced much lower-frequency seismic energy than usually seen in Utah quakes. And one of the main types of seismic waves, shear waves or S-waves, wasn’t detected in the Black Rock sequences.

Volcanoes? In Utah?

PHOTO CREDIT: Paul Gabrielsen

Volcanic rocks found in the Black Rock Desert, Utah.

Download Full-Res Image
All of these signs point to the Black Rock sequences having a very different origin than the Magna sequence, which was generated by movement of the Wasatch Fault. The Black Rock quakes, on the other hand, may have been generated by ongoing activity in the Black Rock volcanic field.

What are volcanoes doing in the middle of Utah? The Wasatch Mountains (and Wasatch Fault) form the eastern margin of a region called the Basin and Range province that stretches west to the Sierra Nevada. The province is being stretched apart by plate tectonics, and that stretching thins the crust, allowing more heat to rise up from the Earth’s interior. In the Black Rock area, that heat resulted in eruption of basalt lava up until around 9,000 to 12,000 years ago.

So what do these earthquake sequences mean for the volcanoes of the Black Rock Desert?

“Our findings suggest that the system is still active and that the earthquakes were probably the result of fluid-related movement in the general area,” Mesimeri says, referring to potentially magma or heated water. “The earthquakes could be the result of the fluid squeezing through rock or the result of deformation from fluid movement that stressed the surface faults.”

Activity in a volcanic field does not mean eruption, and Mesimeri says that there’s no evidence that any eruption is imminent in the Black Rock Desert. But, she says, it’s an area that geoscientists may want to monitor a little more closely.

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Op vrijdag 9 april 2021 00:43 schreef Houtenbeen het volgende:
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‘Hazy skies’ as sulfuric smog from Taal volcano envelops Manila

MANILA: One of the Philippines’ most active volcanoes, Taal, was on Wednesday continuing to release high volumes of the toxic gas sulfur dioxide (SO2) into the skies around the capital region and nearby provinces.

State volcanologists warned residents to stay indoors and wear face masks as a smog enveloped the capital Manila and surrounding areas.

Located 45 miles south of Manila, Taal sits in the middle of a lake and is the country’s smallest but second-most active volcano with a history of deadly explosions.

In a statement, the Philippine Institute of Volcanology and Seismology (Phivolcs) said there was “evidence that the SO2 emitted by Taal had spread to Metro Manila and adjoining areas, causing hazy skies. Phivolcs routinely checks open satellite data information for volcanic SO2 and thermal flux anomalies on monitored active volcanoes in the Philippines.”

The plumes, it added, extended almost 20 kilometers above sea level, and were mainly spread over the Batangas, Laguna, Cavite, Rizal, Bulacan, Pampanga, Bataan, and Zambales provinces and the national capital region.

“Satellite detection on June 29 showed an even larger coverage of Luzon Island,” the institute said, adding that SO2 plumes had reached parts of central and northern Luzon on Tuesday.

Phivolcs noted that the data confirmed its “observation of volcanic smog or vog over the Taal region,” for which an advisory was issued on Monday. On Tuesday, the institute recorded the highest SO2 emission at 14,326 tons per day.

It added that it had initially received public inquiries about the presence of SO2 and vog in Metro Manila and the surrounding provinces but “negated these observations due to the lack of substantiating evidence on our part and the general direction of the wind and SO2 dispersal from Taal to the northeast and east since June 28.

“We also released statements that the haze over Metro Manila is mainly due to smog from human activities,” it said based on interpretation supported by information from the Department of Science and Technology-Philippine Institute of Volcanology and Seismology (Dost-Phivolcs).

Phivolcs pointed out that as a scientific institution, it had been “reminded again of the value of uncertainty and the limitations of our data, the value of citizen observation and the need to challenge our own perceptions, interpretations, and ideas constantly.”

The institute reassured the public that it was “committed to providing the best and most current volcano monitoring data available.”

Meanwhile, it added that an alert level 2 or the threat of sudden steam or gas-driven explosions, volcanic earthquakes, and lethal accumulations or expulsions of volcanic gas “may occur any time” within the Taal volcano island.

“Local government officials are therefore advised to continuously assess and strengthen the preparedness of previously evacuated barangays (villages) around Taal lake in case of renewed unrest.”

Civil aviation authorities were also advised to inform pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from explosions and wind-remobilized ash could pose hazards to aircraft.