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

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Increase in earthquake activity under Lake Taupō, New Zealand

GeoNet is reporting an increase in earthquake activity under Lake Taupō since May 2022. Lake Taupō is a large caldera volcano, a special type of volcano that has rare but unusually large eruptions.

While Lake Taupō sits above the Taupō volcano, the recent earthquakes are not considered to be an indicator that an eruption is on the way, GeoNet scientists said.
This activity is similar to recent periods of elevated earthquakes activity and ground deformation measured in 2008-2009 and 2019.

The Volcanic Alert Level for Taupō Volcanic Centre remains at Level 0.
In 2022, five clusters have been active, beneath the central part of Lake Taupō, north of the lake at Wairakei, Rotokawa, and Ngatamariki, and at Tūrangi.1

The clusters at Wairakei, Rotokawa, and Ngatamariki are generally interpreted as being related to geothermal power development, and the cluster at Tūrangi is probably caused by typical fault movement.

It is the cluster beneath the central part of Lake Taupō, that overlies the Taupō volcano, that has seen an increase in activity since May 2022.

Earthquake activity like this is very typical globally and has been common in the Lake Taupō area, occurring every few years.

This earthquake activity is similar to recent earthquake episodes in 2008-2009 and 2019 under Lake Taupō. Further back, Lake Taupō has seen swarms and earthquake episodes with many more, and larger, earthquakes that have persisted for much longer.

The most active periods of earthquakes occurred in 1895, 1922, 1964-65, and 1983-84.

lake taupo earthquakes january 1 to july 21 2022 bg
Earthquakes located by GeoNet in the Lake Taupō area from January 1 to July 21, 2022. All earthquakes shown here were located less than 30 km deep. There are just over 300 earthquakes shown on the map. Credit: GeoNet
“Earthquake swarms are very common in the Rotorua-Taupō area and larger ones will last weeks to months and include many hundreds of earthquakes,” said GeoNet Duty Volcanologist Agnes Mazot.

“The area under Lake Taupō (both inside and outside of the caldera) has been seismically active since 2000, with just over 5 000 earthquakes located by our instruments. Since the start of May 2022, we have located over 300 earthquakes, mostly beneath the central part of the lake. The earthquakes have been clustered in small groups in various locations.

“The earthquakes this year have ranged in size from about magnitude 1.0 up to 3.6, while 90% of the depths ranged between 4 and 14 km [2.5 – 8.7 miles] below the surface. The largest earthquake in the sequence has been too small to cause any damage, but almost 300 people living in the area reported feeling it.”

Geological summary
Taupo, the most active rhyolitic volcano of the Taupo volcanic zone, is a large, roughly 35 km (21 miles) wide caldera with poorly defined margins. It is a type example of an “inverse volcano” that slopes inward towards the most recent vent location.

The caldera, now filled by Lake Taupo, largely formed as a result of the voluminous eruption of the Oruanui Tephra about 22 600 years before present (BP).

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Op zaterdag 30 juli 2022 20:34 schreef Perrin het volgende:
Het rommelt in Ijsland
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Possibly the first eruption of magma at Ioto volcano in 1 000 years, Japan

The Japan Meteorological Agency (JMA) reports that for the first time in 1 000 years, volcanic eruptions spewing magma are believed to have taken place just off the southern coast of Ioto volcano, also known as Iwoto, Iwojima and Iojima.

Small eruptions started on July 11, 2022, some 900 m (2 950 feet) away from the coast. From July 12 to 15, they occurred every 5 minutes, and continued through the rest of the month, creating water columns up to 30 m (98 feet) high.

Analysis of the rocks that washed ashore on the island showed small cavities inside the rocks, which, officials believe, are cooled lava. In addition, the temperature inside some of the rocks was as high as 120 °C (3.93 °F), JMA said.

Masashi Nagai, a researcher at the National Research Institute for Earth Science and Disaster Resilience (NIED) who specializes in volcanic geology, thinks the most recent magma eruptions were the first since those that occurred about 1 300 years ago.

Earlier this year, the land surface of Ioto island was found to be rising at a rate of 1 m (3.3 feet) per year, which has no parallel elsewhere in the world, JMA said in April 2022.

Nagai’s geological studies showed that Ioto was a large stratovolcano between several hundred thousand years and 100 000 years ago or later. Even then, it might have been a volcanic island with its peak rising above the sea surface.

A large-scale eruption of the volcano occurred about 100 000 years ago, leaving a 10 km (6 miles) wide caldera in its center.

Another large-scale eruption occurred around 2 700 years ago and produced vast volumes of submerged lava and pyroclastic flows. Several further eruptions happened beyond the caldera until around 800 years ago, when Mount Suribachiyama was formed.

It is likely that this is the time when the island began to grow and it hasn’t stopped since.

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The intense seismic activity beneath Lake Taupō (Taupō-nui-a-Tia) continues.

The earthquake swarm itself has occurred at roughly regular intervals of approx. 30 quakes per week. Since the swarm began in May, the rate has been more-less constant, but the local observatory GeoNet New Zealand has registered about 490 events at depth less than 30 km so far.

The distribution of earthquakes has formed into two clusters (see attached image) in the central part of the lake. The smaller, western cluster is located around Karangahape Cliffs and the larger, eastern cluster is centered north-east of Horomatangi Reef.
Another image depicts a number of earthquakes since 2000 including both M 3.6 quakes on 17 May and 11 July.
GPS instruments detected a ground deformation around the lake showing a horizontal uplift by 12 mm.
GeoNet New Zealand continues: Taupō Volcanic Centre is part of the Taupō Volcanic Zone, a tectonically very active region with many known faults and active volcanism. Activity in this region is often related to a mix of regional deformation processes and the magmatic system under the volcanoes. While the observations beneath Lake Taupō to date represent an increase to the normal background activity, they do not stand out with respect to previous periods of unrest in 2008-2009 and 2019 (see Figure 2). We believe that the 2022 earthquakes and ground deformation are similar to those of 2008-2009 and 2019, which has helped to inform our view that Volcanic Alert Level 0 is currently appropriate for the Taupō Volcanic Centre.
The Volcanic Alert Level remains at 0

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Earthquake swarm under Ta’u volcano continues, American Samoa
The earthquake swarm related to Taʻū Island, American Samoa, that started in late July 2022 continues. The Aviation Color Code remains at Yellow.

Data from the new seismometers confirms that the source location of earthquakes has not moved for many days. This tells us that the cause of the earthquakes has not shifted within the earth, the Hawaiian Volcano Observatory (HVO) said on August 30.1

The American Samoa Emergency Operations Center did not receive any felt reports for the past 24 hours. However, the USGS seismic network detected at least 30 earthquakes that were large enough to be felt by people on the Manuʻa Islands.

“It is unclear if this earthquake unrest will escalate to a volcanic eruption and exactly where an eruption might occur,” HVO said.

“An eruption could pose significant hazards to residents of American Samoa; these hazards include volcanic gases, volcanic ash, low-level localized explosions of lava, lava flows, earthquake shaking, and tsunami.”

The primary hazard of concern at this time is earthquake shaking, although no physically damaging earthquakes have occurred as part of this swarm.

In the coming weeks, USGS staff will install Global Positioning System (GPS) receivers to improve the Manuʻa Islands’ monitoring network. The GPS equipment will detect very slight movements of the ground. As a result, GPS data will help us better understand what is happening beneath the ground and provide more accurate hazard assessments.

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Elevated seismic activity prompts closure of Mauna Loa summit
HONOLULU (HawaiiNewsNow) - Elevated seismic activity prompts closure of Mauna Loa summit backcountry until further notice, the Hawaii Volcanoes National Park said Wednesday.

“Mauna Loa is not erupting,” USGS said in an update Wednesday night. They added there is no imminent threat of an eruption and the closure is precautionary.

However, HVO also said the volcano is currently “experiencing heightened unrest.”

According to scientists, the volcanic alert level remains at advisory as of Wednesday night, and the aviation color code remains at yellow.

They recorded 44 small temblors in 24 hours, just below the summit and upper-elevation flanks.

In June, there were up to 10 earthquakes a day. In the past two weeks, there’ve been about 50 a day.

HVO monitoring seismic swarm at Mauna Loa, but says there’s no cause for alarm
Scientists monitoring the seismic waves said they will notify the park if conditions change. USGS will start issuing daily updates.

They also say nearby towns should be ready for a future eruption because the world’s largest active volcano is overdue.

The last time Mauna Loa erupted was in 1984.

HVO said Mauna Loa Road and the Mauna Loa Lookout at 6,662 feet elevation remain open to the public.

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Renewed activity at Anak Krakatau volcano, Indonesia

Eruptive activity at Anak Krakatau volcano, Indonesia increased again over the past two days, with several low-level eruptions. A total of 7 eruptions were recorded from 10:57 UTC on October 24 to 02:49 UTC today, bringing the total number of eruptions since the start of the year to 78.

The first eruption after August 4 took place at 10:57 UTC on October 24, with the height of the ash column observed ± 150 m (490 feet) above the peak (± 307 m / 1 000 feet above sea level).

The column was black with thick intensity towards the northeast. This eruption was recorded on a seismograph with a maximum amplitude of 20 mm and a duration of 32 seconds.

The second eruption took place at 14:11 UTC, with a maximum amplitude of 44 mm and a duration of 47 seconds. Gray to black ash column rose up to about 300 m (1 000 feet) a.s.l.

Four eruptions were recorded on October 25, with ash columns and durations similar to those of the previous day.

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Where will Hawaii's biggest volcano erupt from?

HONOLULU (AP) — The ground is shaking and swelling at Mauna Loa, the largest active volcano in the world, indicating that it could erupt. Scientists say they don't expect that to happen right away but officials on the Big Island of Hawaii are telling residents to be prepared in case it does erupt soon. Here's are some things to know about the volcano.

WHERE IS MAUNA LOA?

Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii, which is the southernmost island in the Hawaiian archipelago. It's not the tallest (that title goes to Mauna Kea) but it's the largest and makes up about half of the island's land mass.

It sits immediately north of Kilauea volcano, which is currently erupting from its summit crater. Kilauea is well-known for a 2018 eruption that destroyed 700 homes and sent rivers of lava spreading across farms and into the ocean.

Mauna Loa last erupted 38 years ago. In written history, dating to 1843, it's erupted 33 times.

The Big Island is mostly rural and is home to cattle ranches, coffee farms and beach resorts. It's about 200 miles (320 kilometers) south of Hawaii's most populous island, Oahu, where the state capital Honolulu and beach resort Waikiki are both located.

WILL MAUNA LOA ERUPT LIKE KILAUEA?

Mauna Loa's eruptions differ from Kilauea's in part because it is taller. It's greater height gives it steeper slopes, which allow lava to rush down its hillsides faster than Kilauea's.

It's enormous size may allow it to store more magma, leading to larger lava flows when an eruption occurs.

Frank Trusdell, research geologist at the Hawaiian Volcano Observatory, which is part of the U.S. Geological Survey, said data indicates that Mauna Loa has a much larger magma reservoir than Kilauea, which may allow it to hold more lava and rest longer between eruptions than Kilauea.

WHERE WILL MAUNA LOA ERUPT FROM?

Scientists won't know until the eruption begins. Each eruption since 1843 started at the summit. Half the time, the volcano later also began erupting from vents at lower elevations. The other half of the time it only erupted in the summit caldera.

Scientists can't tell far in advance when and where Mauna Loa will open new vents and erupt.

Vents generally form along the volcano's rift zone. That's where the mountain is splitting apart, the rock is cracked and relatively weak and it's easier for magma to emerge.

An eruption from vents on the southwest rift zone could hit residential communities, coffee farms or coastal villages on the west side of the island. Lava could reach homes in just hours or days.

The west side's most populous town would be protected from any Mauna Loa eruption by the presence of another active volcano. The broad flanks of that volcano, Hualalai, sit between Mauna Loa's southwest rift zone and Kailua-Kona and would block any lava heading toward the coastal community.

An eruption from the northeast rift zone could send lava toward the county seat of Hilo or other towns in East Hawaii. It could take lava weeks or months to reach populated areas on this side of the mountain.

Scott Rowland, a geologist at the University of Hawaii at Manoa, said there's no pattern when it comes to where an eruption will occur.

“Just because the last one was on the northeast rift zone does not mean the next one will be down the southwest rift zone,” he said.

WILL MAUNA LOA EXPLODE LIKE MOUNT ST. HELENS?

Fifty-seven people died when Washington state's Mount St. Helens erupted in 1980 and blasted more than 1,300 feet (400 meters) off the top of the mountain. Steam, rocks and volcanic gas burst upward and outward. A plume of volcanic ash rose over 80,000 feet (24,384 meters) and rained down as far as 250 miles (400 kilometers) away.

Hawaii volcanoes like Mauna Loa tend not to have explosion eruptions like this.

That's because their magma is hotter, drier and more fluid, said Hannah Dietterich, a research geophysicist at the U.S. Geological Survey's Alaska Volcano Observatory.

The magma in Mount St. Helens tends to be stickier and traps more gas, making it much more likely to explode when it rises.

The gas in the magma of Hawaii’s volcanoes tends to escape, and so lava flows down the side of their mountains when they erupt.

Hawaii's volcanoes are called shield volcanoes because successive lava flows over hundreds of thousands of years build broad mountains that resemble the shape of a warrior's shield.

Shield volcanos are also found in California and Idaho as well as Iceland and the Galapagos Islands. Alaska's Wrangell-St. Elias National Park has eight shield volcanoes including Mount Wrangell.

Volcanoes like Mount St. Helens are called composite or stratovolcanoes. Their steep, conical slopes are built by the eruption of viscous lava flows and rock, ash and gas. Japan's Mount Fuji is another example of a composite volcano.

HOW DO SCIENTISTS MONITOR MAUNA LOA?

The Hawaiian Volcano Observatory has more than 60 GPS stations on Mauna Loa taking measurements to estimate the location and the amount of magma accumulating beneath the surface.

Scientists use tiltmeters to track long-term changes in the tilting of the ground, helping them identify when the ground is swelling or deflating. A rapid change in tilt can indicate when an eruption will occur.

There's also a thermal webcam at Mauna Loa's summit that will identify the presence of heat. And satellite radar can keep track of ground swelling and deflation.

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Op woensdag 2 november 2022 23:35 schreef Perrin het volgende:
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After centuries lying dormant, this Alaska volcano is once again showing signs of life

Eruption unlikely, scientists say, despite rising magma levels below Mt. Edgecumbe in Alaskan panhandle



Mount Edgecumbe pictured on May 19. Scientists traced seismic activity in the Alaskan panhandle to rising magma beneath the mountain, which has not erupted for centuries. (Max Kaufman/Alaska Volcano Observatory)

After centuries of inactivity, a volcano in the Alaskan panhandle has awakened from dormancy.

Scientists have traced a swarm of minor earthquakes around Sitka, Alaska, in 2020 to magma activity below Mount Edgecumbe (L'úx Shaa), around 450 kilometres northwest of Prince Rupert, B.C.

Through computer modelling with satellite radar, scientists at the Alaska Volcano Observatory were able to pinpoint in April that the many small quakes were being caused by rising magma levels below the 976 metre-high peak at the southern end of remote Kruzof Island.

Despite the activity, scientists say an eruption is very unlikely, and no emergency protocols need to be put in place.

Magma causing ground to lift
According to the observatory's findings released last month, the volcanic activity has been brewing since 2018 but remained undetected for several years due to minimal monitoring in the area.

Magma levels have risen by about 10 kilometres from a depth of 20 kilometres since around late 2014, said Ronni Grapenthin, associate professor of geodesy at the University of Alaska and lead author of the study.

The study says the rising magma pools have also caused deformations in the ground around the volcano — the most striking of which is centred just east of the mountain, where an area of around 17 kilometres in diameter has lifted nearly 27 centimetres in less than four years.

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Grapenthin likened the rising magma to an inflating balloon.

"If you have magma that is moving to a shallower depth, it's moving into a space and adds pressure, then the surface on top of that would kind of gently move upwards," he said.

No imminent eruption
Mount Edgecumbe last erupted explosively about 4,000-5,000 years ago, according to Grapenthin. Oral histories from the Klingit Nation in Alaska also cite smaller explosive activity around 900 years ago.

Grapenthin says Edgecumbe is not going to erupt anytime soon.

"The magma is just going to continue to pool where it is and sit there happily. We see that happening a lot around volcanoes. Magma more often just moves to shallower depth and then doesn't erupt," he said.

Max Enders of the U.S. Geological Survey and Max Kaufman of the UAF Geophysical Institute at a temporary seismic station on Crater Ridge, near Mount Edgecumbe. Enders and Kaufman are also with the Alaska Volcano Observatory. ( Max Kaufman/Alaska Volcano Observatory (Submitted by Ronni Grapenthin))
The City of Prince Rupert said its emergency personnel had been made aware of the regional volcanic activity and has reviewed its emergency plans.

"At this point, there has been no local alert or hazard watch issued for our area," it said in a statement to CBC News.

Melanie Kelman, a volcanologist with the Geological Survey of Canada who monitors volcanic hazards, also says an eruption is unlikely.

"It is in an area where there's air traffic above, so obviously, it's a concern for the aviation community if it were to erupt," said Kelman.

"Right now, it's really a sign of showing the speed of magmatic unrest. Often this kind of unrest is not followed by an eruption."

Ongoing monitoring
However, Grapenthin says the risk of an eruption could increase if too much magma moves into the area where it pools, increasing pressure and causing the rock to break.

He also says a large earthquake would increase the probability.

"That would literally shake the magma like you would shake a soda, and that would rapidly increase those pressures," he said.

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Grapenthin says the observatory is still trying to determine what caused the resurgence of volcanic activity. Researchers have installed on-the-ground instrumentation to monitor seismic activity in the area.

Alongside monitoring earthquakes in the area, scientists at the observatory are looking into whether the deformation patterns are changing and if there are any gasses being brought to the surface.

The United States Has a New Volcanic Eruption; Ahyi Seamount

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Remote undersea volcano likely erupting
HONOLULU (AP) - A volcano is likely erupting deep beneath the Pacific Ocean in the U.S. Commonwealth of the Northern Mariana Islands, but scientists don’t know for sure because it’s so inaccessible.

All indications are that the Ahyi Seamount began erupting in mid-October, the U.S. Geological Survey said Monday. The Northern Marianas are about 3,800 miles (6,115 kilometers) west of Honolulu.

Scientists are looking to see if the activity is shallow earthquakes or if material exploded from the crater, said Matt Haney, a USGS research geophysicist. Scientists are checking satellite data to see if there’s discolored water, which could suggest material is coming out of the volcano, he said.

“There’s nothing right now that suggests that this eruption will intensify and become a large eruption,” Haney said.

Still, mariners would want to avoid the immediate area, he said.

Activity from an undersea volcanic source was picked up last month by hydroacoustic sensors some 1,400 miles away (2250 kilometers) at Wake Island.

With help from the the Laboratoire de Geophysique in Tahiti and data from seismic stations in Guam and Japan, scientists analyzed the signals to determine the source of the activity was likely Ahyi Seamount, the USGS said in a statement.

Activity has been declining in recent days, the statement said.

Ahyi seamount is a large conical submarine volcano. Its highest point is 259 feet (79 meters) below the surface of the ocean. It’s located about 11 miles (18 kilometers) southeast of the island of Farallon de Pajaros, also known as Uracas.

“There are no local monitoring stations near Ahyi Seamount, which limits our ability to detect and characterize volcanic unrest there,” the agency said. “We will continue to monitor available remote hydrophonic, seismic, and satellite data closely.”

The seamount is part of the Mariana Volcanic Arc, which is a chain of over 60 active volcanoes stretching over 600 miles west of and parallel to the Mariana Trench, the world’s deepest point.

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Small earthquakes and ground deformation continue at Taupo volcano, New Zealand

Minor volcanic unrest continues at New Zealand’s Taupō volcano, as shown by continued small earthquakes and ground deformation. The Volcanic Alert Level remains at 1. While Volcano Alert Level 1 is mostly associated with environmental hazards, the potential for eruption hazards also exists.

The earthquakes and deformation at Lake Taupō have continued since the last bulletin issued by GeoNet on October 11, 2022.1

The rate of earthquake activity has varied since the increase started in May. After a peak of about 30 – 40 events per week from June to September, the number of earthquakes dropped over the last month to about 10 – 12 per week.

The number has now risen again, over the last two weeks, to a little over 20 events per week.

GeoNet has located 840 earthquakes since the start of 2022, mainly at depths from 4 to 13 km (2.5 – 8 miles) beneath the center of Lake Taupō.

The earthquakes in the last 2 weeks, the largest of which was M3.6 on November 4, have been concentrated in the central portion of the lake, south of Horomatangi Reef.

In addition to seismic activity, GeoNet volcanologists continuously monitor ground deformation (land movement) around Lake Taupō.

Their GNSS (GPS) instruments around the lake continue to observe both horizontal and vertical changes. A site on Horomatangi Reef in the center of the lake indicates that uplift at a rate of approximately 60 ± 20 mm (2.3 ± 0.8 inches) per year has continued since May 2022.

“We interpret the ground deformation and earthquake activity to be caused by activity associated with magma and hydrothermal fluids inside the volcano,” GeoNet Duty Volcanologist Paul Jarvis said.1

“This activity could continue for the coming weeks or months at varying rates or intensities. While some of the earthquakes have been felt in areas around Lake Taupō, the deformation is currently only detectable by our sensitive ground-based monitoring instruments.”

In broad terms, such volcanic unrest occurs when magma or magma-heated hot water and steam moves deep within the ground beneath a volcano, changing the stresses there and producing earthquakes and ground movement. There have been 17 previous episodes of unrest at Taupō over the past 150 years and none have resulted in an eruption, Jarvis noted.

The Volcanic Alert Level (VAL) was raised to Level 1 for Taupō Volcano on September 20, 2022. This was based on the current data but was also supported by new knowledge from research programs on volcanic eruptions and unrest at Taupō Volcano.

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El Salvador on alert near Chaparrastique volcano

Authorities in El Salvador have warned residents near the Chaparrastique volcano in the country's east to be alert after it began to erupt on Sunday.

The Environmental Ministry's observatory reported explosions in the central crater of the volcano located about 83 miles (135km) east of the capital. It said the eruption's intensity was a 1 on a scale from 0 to 8.

The eruption began when the volcano launched rock and ash to areas surrounding the crater. There were no reported injuries.

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Unrest observed at Ahyi Seamount, Aviation Color Code raised to Yellow, Northern Mariana Islands

Satellite and remote geophysical data show signs of unrest at Ahyi Seamount, Northern Mariana Islands, prompting the USGS to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory on November 28, 2022.

While marine hazards are already possible above or near the volcano, aviation hazards are possible only in event of increased activity.
Signs of unrest at Ahyi Seamount have been observed in satellite and remote geophysical data. A plume of discolored water above Ahyi Seamount has been visible persistently in satellite data since November 18, 2022.

This discoloration could be due to degassing or eruption at the volcano, but we cannot say for certain due to a lack of local monitoring stations.1

Starting in mid-October, hydroacoustic sensors at Wake Island, 2 270 km (1 410 miles) east of Ahyi, began recording signals consistent with activity from an undersea volcanic source.

In collaboration with the Laboratoire de Geophysique in Tahiti, a recent combined analysis of the hydroacoustic signals together with data from seismic stations located at Guam and Chichijima Island, Japan, confirm that the source of this activity is at or near Ahyi seamount. Hydrophone signals continue to be observed but have decreased in the past few weeks.

Due to the current activity, the aviation color code is being raised from Unassigned to Yellow and the Alert Level from Unassigned to Advisory.