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

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Mount St. Helens experiences largest seismic increase since last eruption ended in 2008

Elevated seismic activity has been observed at Mount St. Helens in the United States since July 15, 2023 — representing the largest short-term increase in earthquake rates since the last eruption ended in 2008. No significant changes have been observed in other monitoring parameters and there are no signs of an imminent eruption.

Mount St. Helens has experienced a noticeable uptick in seismic activity over the past three months, with more than 400 earthquakes located by the Pacific Northwest Seismic Network since July 15. The frequency peaked in late August to early September, recording 40 to 50 earthquakes per week. In recent times, this figure has stabilized at around 30 earthquakes per week. For comparison, the average number of monthly earthquakes since 2008 is approximately 11.

The most substantial earthquake during this period registered at a magnitude of 2.4 on August 27. The depth of these seismic events ranged between 2 km and 6 km (1.2 and 3.7 miles) below sea level, translating to approximately 4 to 8 km (2.5 to 5 miles) below the crater floor. Despite the increased seismicity, no alterations have been observed in ground deformation, volcanic gas, or thermal emissions.

This recent activity marks the most significant short-term increase in earthquake rates at Mount St. Helens since the last eruption ended in 2008. Yet, the volcano remains at a normal Alert Level, and the Aviation Color Code is still Green. Past seismic sequences with even higher event counts occurred in 1988 – 1992, 1995 – 1996, and 1997 – 1999. None of these sequences led to eruptions.

The earthquakes are generally considered to be associated with the pressurization of the magma transport system. This pressurization can be caused by the arrival of additional magma, a process known as recharge. The volcano is fed by magma originating near the base of the crust at depths of about 25 km (~16 miles). This magma then ascends and accumulates in a reservoir situated 4 to 10 km (~2.5 to 6 miles) below sea level. Recharge events can trigger increased stresses that result in earthquakes.

There have been no significant changes in hazards at Mount St. Helens as a result of this activity.

Mount St. Helens has a complex geological history that spans tens of thousands of years. Prior to its devastating eruption in 1980 (VEI 5), the volcano exhibited a conical shape, earning it the nickname “Fujisan of America.” The 1980 event significantly altered the volcano’s topography by removing the upper 400 m (1 312 feet) of its summit through slope failure. This resulted in a 2 x 3.5 km (1.24 x 2.17 miles) breached crater, which has since been partially filled by a subsequent lava dome.

The volcano has seen nine major eruptive periods, with the earliest starting approximately 40 to 50 000 years ago. Its activity during the Holocene epoch has made it the most active member of the Cascade Range, a mountain range that includes several other volcanoes.

The older edifice of Mount St. Helens was primarily formed through the eruption of tephra, lava domes, and pyroclastic flows. These eruptions took place before 2 200 years ago and contributed to the mountain’s structure, although few lava flows extended beyond its base at that time. The modern edifice consists of a variety of geological materials, including basalt as well as andesitic and dacitic products, originating from both the summit and flank vents.

Eruptions in the 19th century were notably different, originating from the Goat Rocks area on the northern flank of the volcano. These eruptions were among the first to be witnessed by early settlers in the region.

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Op maandag 20 november 2023 20:25 schreef -CRASH- het volgende:

More Injected Magma Causes Uplift in Iceland: Geologist Reviews the Latest Data and Info

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Marapi-vulkaan op Indonesische eiland Sumatra barst uit, elf klimmers dood

Op het Indonesische eiland Sumatra zijn de lichamen van elf bergbeklimmers gevonden. Ze zijn om het leven gekomen na een uitbarsting van de Marapi-vulkaan. Drie mensen zijn levend teruggevonden. Nog twaalf anderen worden vermist, maar de zoektocht is tijdelijk stilgelegd vanwege een kleinere nieuwe uitbarsting.

Eerder op de dag werd duidelijk dat er 75 bergbeklimmers in de omgeving van de Marapi waren ten tijde van de uitbarsting. 49 van hen konden al snel geëvacueerd worden. Velen hebben brandwonden opgelopen en worden daarvoor behandeld.

De bijna 2900 meter hoge vulkaan op West-Sumatra, niet te verwarren met de Merapi-vulkaan op Java, barstte gisteren uit en spuwde as tot 3 kilometer hoogte de lucht in. De autoriteiten hebben omwonenden opgedragen om 3 kilometer afstand te houden van de vulkaan. De op een na hoogste veiligheidswaarschuwing is van kracht.

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Dodental uitbarsting Marapi-vulkaan Sumatra loopt op naar 22

Het dodental na de uitbarsting van de Marapi-vulkaan op het Indonesische eiland Sumatra - niet te verwarren met de Merapi op Java - is opgelopen tot 22. De lichamen van vijf slachtoffers zijn geborgen. Een persoon wordt nog vermist.

Het bereiken van de overleden bergbeklimmers wordt bemoeilijkt door de gevaarlijke omstandigheden: uitbarstingen veroorzaken hete wind en de hellingen van de vulkaan zijn erg steil. Er zijn zo'n 200 bergingswerkers ingezet.

Bij de eerste uitbarsting op zondag kwamen de aswolken tot wel 3 kilometer hoog. 49 klimmers konden toen worden geëvacueerd. Gisteren werden de zoekacties tijdelijk gestaakt vanwege een tweede uitbarsting, waarbij de hete as van de vulkaan tot wel 800 meter hoog de lucht in spoot.

Dorpen op zo'n 5 à 6 kilometer van vulkaan werden bedekt met puin. Omwonenden van de vulkaan kregen het advies mondkapjes en brillen te dragen, om zichzelf tegen de as te beschermen.

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Phreatic eruption, pyroclastic flows at Mayon volcano, Philippines

A phreatic eruption occurred at the Mayon volcano summit on Sunday, February 4, 2024, at 08:37 UTC, lasting 169 seconds. The event generated a 1 200 m (4 000 feet) tall ash plume, rockfalls and pyroclastic flows. The volcano’s Alert Level remains at 2 and authorities are reminding the public to avoid the Permanent Danger Zone.

On Sunday, February 4, 2024, at 08:37 UTC (16:37 local time), the Mayon Volcano in the Philippines erupted in a phreatic explosion that lasted for approximately 169 seconds. The eruption was characterized by a booming sound, the occurrence of rockfall, pyroclastic density currents (PDC), and the generation of a 1 200 m (4 000 feet) tall plume that drifted southwest. This is about 3.6 km (12 000 feet) above sea level.

Following the eruption, the Philippine Institute of Volcanology and Seismology (Phivolcs) has reiterated the importance of not entering the 6 km (3.7 miles) Permanent Danger Zone (PDZ) surrounding the volcano due to the potential hazards such as sudden steam-driven eruptions, landslides, and lahars, especially during heavy and prolonged rainfall.

Mayon Volcano, known for its perfect cone shape and as the most active volcano in the Philippines, remains at Alert Level 2, indicating a moderate level of unrest.

The volcano, which rises majestically above the Albay Gulf northwest of Legazpi City, has a history of eruptions dating back to 1616 CE, ranging from Strombolian to basaltic Plinian types.

Its eruptive history is marked by cyclical activity that typically begins with basaltic eruptions, followed by andesitic lava flows that have occasionally reached populated areas, causing significant damage and fatalities. The 1814 eruption, one of its most violent, resulted in over 1 200 deaths and widespread destruction.

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Ash produced by Popo extends more than 250 km
Increased eruptive activity continues at Mexico’s Popocatepetl volcano on March 1, 2024. The activity over the past 24 hours consisted of 148 exhalations and 1 034 minutes of tremor.

Satellite images below, captured on February 28, show a large ash column reaching up to 6.7 km (22 000 feet) above sea level and extending for more than 250 km (155 miles) from the top of the volcano into the Gulf of Mexico:

Mexico City’s Benito Juárez International Airport (AICM), while confirming its operational status, has reported cancellations of 22 domestic and international flights due to the ash, which has also prompted safety checks following incidents of planes encountering ash en route to the capital.

Slight ashfall was reported in the municipalities of Hueyapan, Yecapixtla and Tetela del Volcán, Morelos; in Ixtacuixtla, Panotla, Tepetitla, Nativitas, Zacatelco, Santa Apolonia Teacalco, San Damián Texóloc, Tetlahuaca, Zacatelco, Xicohtzingo, Papalotla, Tenancingo, Santa Catarina Ayometla, Magdalena Tlaltelulco, San Francisco Tetlanohcan and Teolocholco, Tlaxcala; in Iztacalco, Iztapalapa and Coyoacán, Mexico City; and finally in Atlautla, Ayapango, Ecatzingo, Chalco, Tenango del Aire, Temamatla, Ozumba, Tepetlixpa, Tlalmanalco and Amecameca, State of Mexico.

The alert status remains at Level 2. Residents and tourists are advised not to approach the crater within 12 km (7.4 miles) radius.

Authorities warned residents that lahars could occur if heavy rainfall remobilizes these fresh ash deposits.

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Short-lived explosion at Atka volcanic complex, Aviation Color Code raised to Yellow, Alaska

A small, short-lived explosion was detected at the Atka volcanic complex in Alaska at 03:36 UTC on March 28, 2024 (19:36 AKDT on March 27).

As a result, the Alaska Volcano Observatory (AVO) has raised the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory.

The event was detected in local infrasound and seismic data and was followed by a few minutes of elevated seismic tremor. Processing of the local infrasound data indicates the explosion originated from the summit crater of Korovin, one of several volcanoes within the Atka volcanic complex. No ash emissions have been observed in satellite images, AVO added.

The last eruptive period at this volcano lasted from November 2006 to March 2007 (VEI 1). The volcano has a history of VEI 1 to 3 eruptions since 1812.

The Atka Volcanic Complex consists of a central shield and Pleistocene caldera with several post-caldera volcanoes. A major dacitic explosive eruption accompanied the formation of the caldera about 500 000 to 300 000 years ago. The most prominent of the post-caldera stratovolcanoes are Kliuchef and Sarichef, both of which may have been active in historical times.

This is the largest (approximately 200 km3 / 48.2 mi3) volcanic center in the central Aleutians. The closest town is Atka (16 km / 10 miles) SW of the volcano, with a population of 71.

Hot springs and fumaroles are located on the flanks of Mount Kliuchef and in a glacial valley SW of Kliuchef.

Korovin, at the NE tip of Atka Island, is the most frequently active volcano of the complex, and contains a double summit with two craters. The NW summit has a small crater, but the 1-km-wide (0.6 miles) crater of the SE cone has an open cylindrical vent of widely variable depth that sometimes contains a crater lake or a high magma column.

A fresh-looking cinder cone lies on the flank of the partially dissected Konia volcano, located on the SE flank of the dominantly basaltic Korovin. Some late-stage dacitic lava flows are present on both Korovin and Konia.

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Eruption of Ruang volcano
A series of powerful eruptions took place at Ruang volcano in Indonesia’s North Sulawesi province starting at 17:08 UTC on April 16, 2024 (01:08 LT, April 17). As a result, the Aviation Color Code was raised to Red, the Alert Level to 3 of 4, and local authorities started evacuating more than 800 people living on the island as a preventive measure. The last eruptive episode at this volcano was in September 2002 (VEI 4).

Authorities have raised the alert level to the second highest level (3 of 4), Heruningtyas Desi Purnamasari, an official at Indonesia’s Center for Volcanology and Geological Hazard Mitigation (PVMBG) said, adding that the eruptions were triggered by recent earthquakes on the island.